2 Chapter 4: Heredity and Reproduction

Transcription

1 Genetic Processes UNIT 2 Chapter 4: Heredity and Reproduction Genetic information is passed from one generation to the next by the process of reproduction. This genetic information is stored in DNA molecules, which are organized into genes on chromosomes. There are two types of reproduction. Asexual reproduction involves one parent, producing offspring that are genetically identical to the parent. Sexual reproduction involves two parents, producing genetically variable offspring. Each of these processes has biological advantages and disadvantages. Information about sexual and asexual reproduction, and how genetic information is transmitted during these processes, has applications related to human health, to agriculture, and to the environment. BIG IDEAS Genetic and genomic research can have social and environmental implications. Variability and diversity of organisms result from the distribution of genetic materials during the process of meiosis. Chapter 5: Mendelian Genetics Patterns of Inheritance Our understanding of how traits are transmitted during reproduction is due largely to the work of Gregor Mendel, the Father of Genetics. He used the results of many experiments to develop laws describing the inheritance of traits. There are many patterns of inheritance beyond those studied by Mendel. Patterns of inheritance include complete dominance, incomplete dominance, and codominance. Some traits, such as human skin colour, are controlled by multiple pairs of alleles, resulting in a great amount of variation. Genetic factors play a role in many disorders, such as cystic fibrosis. Genetic screening and carrier testing can help determine the risk of expressing or passing on a genetic disorder. However, there are social and ethical implications in the use of genetic screening and carrier testing. Chapter 6: Genetics beyond Mendel Genetic information is stored in DNA molecules. DNA is a double helix consisting of pentose sugars, phosphate groups, and nitrogenous bases. Mutations, which are changes in the sequence of nitrogenous bases in DNA, can occur due to environmental factors or errors in replication. Genomes of different organisms contain different numbers of genes. The human genome, which consists of about genes, has been sequenced, and this information can be used in medical and forensic applications. Genetic engineering uses a variety of techniques to manipulate genetic information. Gene therapy applies genetic engineering to overcome the effects of defective genes. Genetic engineering and gene therapy have social and environmental considerations. Manipulation of the genome has environmental and social considerations. NEL Unit 2 Genetic Processes 1 Bio11SG_U2Ch04_P01.indd 1 1/14/11 7:45:34 PM

2 4.1 The Nature of Heredity Textbook pp Vocabulary heredity deoxyribonucleic acid (DNA) locus polyploid genetics gene sexual reproduction asexual reproduction MAIN IDEA: Chromosomes carry information for traits, and traits are passed from parents to offspring in a process known as heredity. 1. Genetic material includes deoxyribonucleic acid (DNA), chromosomes, and genes. Create a graphic organizer to show the relationship between these terms. T / I C chromosomes contain genes which are portions of DNA molecules 2. List three ways in which chromosomes may vary from species to species. K/U 3. How are the terms gene, locus, and chromosomes related? T / I 4. Each gene carries information related to a specific. K/U MAIN IDEA: Each species has a characteristic number of chromosomes per body cell. Body cells and gemmates (sex cells) have different numbers of chromosomes. 5. Explain the difference between haploid and diploid cells, in terms of chromosomes. T / I 6. Using the values in Table 1, determine the following (a) the number of chromosomes in a haploid dog cell. T / I (b) the number of pairs of chromosomes in each human body cell. T / I Table 1 Chromosome Numbers in Assorted Species Species Chromosome number per body cell human 46 dog 78 mosquito 6 banana 22 2 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 2 1/14/11 7:45:34 PM

3 MAIN IDEA: Asexual reproduction almost always involves cell division and results in offspring that are genetically identical to their single parent. 7. Fill in Table 2 below to describe asexual reproduction. T / I Table 2 Asexual Reproduction Number of parents Biological advantage(s) Resulting offspring 8. What are some disadvantages of asexual reproduction? T / I MAIN IDEA: Sexual reproduction results in offspring that are genetically variable. Offspring inherit half of their genetic information from each of two parents. 9. Fill in Table 3 to describe sexual reproduction. T / I Table 3 Sexual Reproduction Number of parents Biological advantage(s) STUDY TIP Tables You can use tables to organize information about the two main types of reproduction. After the tables are completed, use them to compare these processes. Resulting offspring 10. Describe a possible scenario in which asexual reproduction might be more advantageous than sexual reproduction. T / I A 11. How might an organism benefit from being able to reproduce both asexually and sexually? NEL 4.1 The Nature of Heredity 3 Bio11SG_U2Ch04_P01.indd 3 1/14/11 7:45:35 PM

4 Textbook pp Asexual Reproduction: Copies and Clones Vocabulary fragmentation mitosis chromatin sister chromatid cloning biotechnology genetically modifi ed organism interphase cytokinesis MAIN IDEA: Asexual reproduction is the most common form of reproduction among unicellular organisms and is also widespread among many multicellular organisms particularly plants and fungi. 1. Among which species is asexual reproduction relatively rare? Provide a possible explanation for this. T / I 2. Complete Table 1 by writing a short description of how each organism undergoes asexual reproduction. K/U Table 1 Organisms that Undergo Asexual Reproduction Type of organism strawberry plants Mode of asexual reproduction (a) hydrae (b) aphids (c) fungi (d) LEARNING TIP Chromosome Composition An unduplicated chromosome is made up of a single DNA molecule and its associated proteins. MAIN IDEA: Cells divide during mitosis and cytokinesis. Cell division produces two daughter cells that are genetically identical to each other and to the original parent cell. 3. is the stage of the cell cycle during which the genetic material in the nucleus is divided equally into new cells. K/U 4. is the stage of the cell cycle during which the cell cytoplasm is divided. K/U 5. The mass of thread-like structures composed of DNA and proteins is called. K/U 6. The replication of chromosomes during interphase results in pairs of (a) chromatids (b) chromosomes (c) sister chromatids (d) homologous chromosomes K/U 4 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 4 1/14/11 7:45:35 PM

5 7. Sister chromatids contain the same, found at the same, and are held together by the. K/U 8. Place the following stages of mitosis in order: anaphase, telophase, metaphase, and prophase. K/U (i) (ii) (iii) (iv) 9. Match the stages of mitosis to the sentence that best describes it. K/U (a) prophase (i) centromeres divide and chromosomes move to opposite poles of the cell (b) anaphase (ii) the first phase, during which chromosomes shorten and thicken (c) telophase (iii) spindle fibres move and align the chromosomes (d) metaphase (iv) chromosomes reach opposite poles of the cell and begin to unwind MAIN IDEA: Biotechnology has many applications that are used to benefi t society, but also has potentially negative implications. 10. Clones have little or no genetic. K/U 11. Compare the genetic makeup of a clone to the genetic makeup of the parent organism. T / I 12. Write a sentence that explains the role of each of the following organisms in the cloning of an adult mammal. K/U C (a) The surrogate mother: STUDY TIP Contrasting Contrasting, or differentiating, two processes can help you learn about each of the processes. Use this skill to learn about the stages of mitosis. Differentiate each of the stages, explaining how each differs from the others. LEARNING TIP Differentiation Dead-End An unfertilized egg cell grows and differentiates into a specialized cell with a specifi c function. Once the cell has differentiated, it loses its ability to change into a different kind of cell. (b) The egg cell donor: (c) The adult mammal to be cloned: 13. List two problems that tend to develop in mammals produced by cloning. K/U (i) (ii) 14. List three applications of biotechnology. K/U 15. Identify and describe an advantage of using cloning to produce livestock and crop plants. K/U NEL 4.2 Asexual Reproduction: Copies and Clones 5 Bio11SG_U2Ch04_P01.indd 5 1/14/11 7:45:35 PM

6 16. Why are cloned plants and animals more vulnerable to changes in the environment and new diseases than populations that exhibit genetic variability? T / I A 17. Describe a situation in which the genetic consistency of cloned livestock organisms is a risk rather than a benefit. Explain your response. T / I A 18. Identify one reason why cloning is used instead of captive breeding in some situations to increase the population of endangered species. K/U T / I 6 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 6 1/14/11 7:45:35 PM

7 Sexual Reproduction: Adding Variety Vocabulary gamete fertilization zygote ova meiosis homologous chromosome tetrad synapsis crossing over gametogenesis spermatogenesis oogenesis karyotype sex chromosomes autosomes 4.3 Textbook pp MAIN IDEA: Sexual reproduction produces genetically variable offspring by combining the genetic information from two parents. 1. Identify and describe the two key processes that occur in sexual reproduction. T / I 2. Fill in Table 1 with what you know about human sex cells. K/U Table 1 Human Sex Cells Reproductive organs that produce sex cells Name of sex cell female male MAIN IDEA: During meiosis, diploid cells undergo two cell divisions, resulting in haploid cells. 3. Compare the number of chromosomes in daughter cells produced by mitosis to the number of daughter cells produced by meiosis. T / I 4. Use a diagram to explain the difference between sister chromatids and homologous chromosomes. T / I homologous chromosomes sister chromatids NEL 4.3 Sexual Reproduction: Adding Variety 7 Bio11SG_U2Ch04_P01.indd 7 1/14/11 7:45:35 PM

8 5. Explain why the term independent assortment is appropriate to describe how homologous chromosomes are sorted during meiosis I. T / I STUDY TIP Defining Terms Defi ning terms related to a process can increase your understanding of the process as a whole. Work with a partner to review the defi nition of each of the vocabulary terms for this lesson. MAIN IDEA: Meiosis I divides homologous chromosomes. Homologous chromosomes are assorted independently of other pairs. 6. Define the following terms related to meiosis I: K/U (a) Tetrad: (b) Synapsis: (c) Crossing over: 7. The exchange of chromosomes genetic information is known as, and occurs during. K/U 8. How does crossing over contribute to genetic diversity? K/U MAIN IDEA: Meiosis II divides sister chromatids. 9. The formation of genetically variable sex cells in meiosis II is called. K/U 10. Add the following labels to Figure 1: first meiotic division, first polar body, oogenesis, ovum, three polar bodies, second meiotic division, spermatogenesis, sperm cells. K/U (a) (b) 46 chromosome number (c) (g) (d) (e) (f) (h) 8 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 8 1/14/11 7:45:35 PM

9 MAIN IDEA: Mammals have X and Y sex chromosomes and use an XX/XY system for female/male sex determination; however, there are many different sex-determination systems in living things. 11. Contrast the sex-determination mechanism of mammals with the sexdetermination mechanism of turtles and crocodiles. T / I 12. Figure 1 below represents the sex chromosomes of two individual mammals. (a) Under each diagram, write the term XX or XY. K/U (b) Circle the diagram that represents a male mammal. Figure 1 Sex chromosomes NEL Bio11SG_U2Ch04_P01.indd Sexual Reproduction: Adding Variety 9 1/14/11 7:45:36 PM

10 Textbook pp Abnormal Meiosis and/or Fertilization Vocabulary non-disjunction trisomy monosomy Down syndrome prenatal testing MAIN IDEA: Errors in meiosis can result in abnormal numbers of chromosomes and can cause serious genetic disorders. 1. When homologous chromosomes fail to separate during meiosis the result is an abnormal number of in daughter cells. K/U 2. Fill in Table 1 below by identifying the non-disjunction disorder associated with each chromosome abnormality. K/U Table 1 Nondisjunction Disorders Non-disjunction disorder (a) Chromosome abnormality One X chromosome, no Y chromosome (b) Trisomy 21 (c) Two X chromosomes and one Y chromosome MAIN IDEA: Karyotypes can be used to evaluate chromosome numbers and diagnose genetic disorders. 3. What evidence in a karyotype would lead to a diagnosis of Patau syndrome? K/U 4. Explain why karyotypes are an effective way to diagnose non-disjunction disorders. T / I MAIN IDEA: Prenatal testing can be used to determine the likelihood of certain genetic disorders. 5. and are types of prenatal testing in which fetal cells are collected and analysed. K/U 6. is a type of prenatal screening that tests hormone levels. K/U 10 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 10 1/14/11 7:45:36 PM

11 MAIN IDEA: Assisted reproductive technologies (ARTs) are technologies used to enhance the chances of reproductive success. 7. Fill in the concept map below to show the relationship between these terms: artificial insemination, in vitro fertilization, assisted reproductive technologies, intracytoplasmic sperm injection, and laser-assisted hatching. T / I (a) Assisted reproductive technologies include (b) STUDY TIP Concept Maps You can use a concept map to show the relationship between concepts or ideas. In this section, you can use a concept map to show the relationship between various assisted reproductive technologies. Try making one other concept map that shows the relationship between other concepts in this lesson. which can be made more successful using (c) (d) MAIN IDEA: There are many applications of reproductive technologies in agriculture, industry, and wildlife conservation. 8. The use of artificial insemination in wildlife conservation has benefits and costs. List two benefits and a cost below. K/U (a) Benefits: (b) Cost: MAIN IDEA: The use of many reproductive technologies is highly controversial. 9. Write one or two sentences to support the following statement: Regardless of an individual s position on the moral and ethical implications of reproductive technologies, it is important to understand the science behind these technologies. T / I C A NEL 4.4 Abnormal Meiosis and/or Fertilization 11 Bio11SG_U2Ch04_P01.indd 11 1/14/11 7:45:36 PM

12 4.5 Cytoplasmic Inheritance Textbook pp Vocabulary maternal inheritance paternal inheritance horizontal gene transfer MAIN IDEA: Mitochondria and chloroplasts contain genetic material and are able to reproduce independently within the cytoplasm of the cell. 1. The DNA found in mitochondria and chloroplasts contains the necessary for the proper functioning of the. K/U 2. The genes in mitochondria contain information related to the process of. K/U 3. The genes in chloroplasts contain information related to the process of. K/U 4. Mitochondria originated as organisms. K/U 5. Chloroplasts originated as organisms. K/U STUDY TIP Comparing and Contrasting Comparing and contrasting can help you learn about the characteristics of objects and processes. Work with a partner to compare and contrast chloroplasts and mitochondria. MAIN IDEA: The DNA in mitochondria and chloroplasts is usually inherited maternally. 6. Compare and contrast the inheritance of mitochondrial DNA to that of nuclear DNA. T / I C 7. Define the following terms: K/U (a) Maternal inheritance: (b) Paternal inheritance: MAIN IDEA: The combination of genetic variation within organelles and the random assortment of organelles into daughter cells can produce genetic variation within the cells of individuals. 8. Write a short paragraph that explains genetic variation within organelles, using plants with variegated leaves as an example. K/U C 12 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 12 1/14/11 7:45:37 PM

13 MAIN IDEA: Some observable characteristics and genetic disorders are inherited through mitochondrial DNA. 9. A genetic disorder related to energy metabolism is likely due to changes in the DNA of the. K/U 10. Describe the process of DNA egg swapping, as it relates to mitochondrial diseases. T / I C MAIN IDEA: Horizontal gene transfer can result in one organism exhibiting a characteristic of an entirely different organism. 11. Define the term horizontal gene transfer and give an example. K/U NEL 4.5 Cytoplasmic Inheritance 13 Bio11SG_U2Ch04_P01.indd 13 1/14/11 7:45:37 PM

14 CHAPTER 4 SUMMARY Heredity and Reproduction Genetic information is passed from one generation to the next in the process of reproduction. Information about the processes involved can be used to benefit society and human health. Genetic information is contained in DNA, in the form of genes which are found on chromosomes that are passed to of spring during reproduction which can be sexual asexual which produces which produces variable of spring identical of spring called natural clones and requires the process of and requires the process of which can also be produced by meiosis cell division (mitosis and cytokinesis) biotechnology (artificial clones) 14 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 14 1/14/11 7:45:37 PM

15 CHAPTER 4 QUESTIONS For each question, select the best answer from the four alternatives. 1. Which best summarizes the source of genetic information in offspring produced in the process of sexual reproduction? (4.1) K/U (a) Genetic information from both parents is present in the offspring. (b) Genetic information from only the father is present in the offspring. (c) Completely new genetic information is generated in the offspring. (d) Genetic information from only the mother is present in the offspring. K/U Knowledge/Understanding T / I Thinking/Investigation C Communication A Application 2. Cells formed by the process of gametogenesis are (4.3) K/U (a) diploid (b) haploid (c) polyploid (d) homologous Indicate whether each of the statements is true or false. If you think the statement is false, rewrite it to make it true. 3. A karyotype can be used to determine how many genes an organism has. (4.4) K/U 4. Multiple marker screening is one type of prenatal testing. (4.5) K/U Respond to each statement or answer each question below. 5. Do you think cloning will ever completely replace sexual reproduction as a means of producing farm animals? Explain why or why not. (4.2) T / I A 6. Explain what would happen if crossing over stopped occurring in a particular species. (4.3) T / I 7. Define the term non-disjunction, and infer why non-disjunction disorders typically have drastic effects on phenotype. (4.4) T / I 8. Contrast the inheritance of nuclear genetic material and cytoplasmic genetic material during human reproduction, and explain why this difference is significant. (4.4, 4.5) T / I NEL Chapter 4 Questions 15 Bio11SG_U2Ch04_P01.indd 15 1/14/11 7:45:37 PM

16 Complete the following graphic organizers. 9. Complete the following comparison matrix to compare asexual reproduction and sexual reproduction. (4.1, 4.2, 4.3) T / I C A Asexual reproduction Sexual reproduction Number of parents Key cellular process Result Biological advantage Biological disadvantage 10. Sequence and describe the phases of mitosis in the following flow chart. (4.2) T / I C A (a) (b) (c) (d) S S S 11. In the space below, make a Venn diagram below that compares the processes of meiosis and mitosis. (4.1, 4.2, 4.3) T / I C A 16 Unit 2 Genetic Processes NEL Bio11SG_U2Ch04_P01.indd 16 1/14/11 7:45:37 PM

17 Mendelian Inheritance 5.1 Vocabulary trait F 1 generation allele dominant allele Textbook pp true-breeding organism monohybrid homozygous recessive allele hybrid monohybrid cross heterozygous Punnett square cross F 2 generation genotype probability P generation law of segregation phenotype test cross MAIN IDEA: Gregor Mendel was the fi rst person to record and quantify the inheritance of traits in an organism over many generations. He did this through the selective crossbreeding of common pea plants (Pisum sativum). His experiments laid the groundwork for modern day genetics. 1. Why did Mendel select the pea plant for his experiments? Give three characteristics of the pea plant that make it ideal for crosses. 2. Explain the significance of Mendel s use of true-breeding plants in his experiments. LEARNING TIP Characteristic or Trait Do not confuse the terms characteristic and trait. Traits represent the variation within a characteristic. For example, height is a characteristic, while short and tall are traits; sight is a characteristic, while normal vision, nearsightedness, and far-sightedness are traits. 3. Explain how the characteristics that Mendel chose to study aided his study of the inheritance of traits. 4. Define monohybrid cross and explain its significance in experiments that study the inheritance of traits. NEL 5.1 Mendelian Inheritance 17 Bio11SG_U2Ch05_P01.indd 17 1/14/11 8:30:29 PM

18 MAIN IDEA: Mendel s data revealed patterns of inheritance. Table 1 Mendel s Data Characteristics P F 1 F 2 Ratio seed shape round wrinkled all round 5474 round 1850 wrinkled seed colour yellow green all yellow 6022 yellow 2001 green pod shape infl ated constricted all infl ated 882 inflated 299 constricted pod colour green yellow all green 428 green 152 yellow fl ower colour purple white all purple 705 purple 224 white fl ower position axial terminal all axial 651 axial 207 terminal stem length tall dwarf all tall 787 tall 277 dwarf 2.96 : : : : : : : 1 5. (a) Write a sentence that summarizes the mathematical pattern in Mendel s data for the F 1 generation (Table 1). (b) Write a sentence that summarizes the mathematical pattern in Mendel s data for the F 2 generation (Table 1). T / I C 6. (a) What were Mendel s two main conclusions about how traits are passed from one generation to the next? (b) What is the formal name used to describe Mendel s two conclusions? K/U LEARNING TIP Dominance In genetics, dominance refers only to which gene is expressed in an organism. It does not mean that the dominant allele is stronger, better, or more common than the recessive allele. MAIN IDEA: Genes have alternate forms called alleles. 7. A(n) is any of the alternate forms of a gene that may occur at a specific locus. K/U 8. Cells have two alleles for each gene, one from each parent. If the two alleles for a particular gene are the same, the individual is for that allele. If the two alleles for a particular gene are different, the individual is for that allele. K/U MAIN IDEA: Genes infl uence traits. 9. The set of alleles an individual has, or its genetic makeup, is known as its. K/U 10. An individual s outward appearance with respect to a specific characteristic is its. K/U 18 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 18 1/14/11 8:30:30 PM

19 11. Some alleles are dominant, while others are recessive. alleles are always expressed in the phenotype, whereas alleles do not show up unless they are the only allele present in the genotype. K/U Use Figure 1 to answer questions 12 and 13. TT Figure Based on the information in Figure 1, which allele for plant height is dominant? T / I 13. Circle any plant or plants shown in Figure 1 that are homozygous. Cross out any plant or plants that are heterozygous. K/U Tt tt 14. Explain how two different genotypes may result in the same phenotype. K/U MAIN IDEA: A Punnett square is a diagram used to predict the proportions of genotypes in the offspring resulting from a cross between two individuals. 15. (a) What does the information on each axis of a Punnett square represent? (b) What does the information inside a Punnett square represent? K/U 16. In pea plants, the trait of axial flowers, A, is dominant, and the trait of terminal flowers, a, is recessive. Draw a Punnett square in the space below that shows a cross between two pea plants heterozygous for the trait of flower position. The genotype of each parent plant is Aa. T / I C A a STUDY TIP Punnett Square A Punnet square can be used to predict the inheritance of alleles. Use a Punnett square when you are asked to fi nd the possible genotypes of offspring that result from a cross. A AA Aa a Aa aa Explain how a test cross can be used to determine the genotype of an unknown parent. K/U NEL 5.1 Mendelian Inheritance 19 Bio11SG_U2Ch05_P01.indd 19 1/14/11 8:30:30 PM

20 5.2 Variations in Heredity Textbook pp Vocabulary complete dominance incomplete dominance codominance LEARNING TIP Notation of Alleles Notation of alleles for a specifi c gene can be represented using superscripts. For example, consider the alleles for colour in snapdragons. The gene is C for colour. The alleles are red (R ) and white (W ). When you combine the notations for genes and alleles, the result is C R for the red allele and C W for the white allele. MAIN IDEA: Alleles that determine the phenotype regardless of the presence of other alleles follow a pattern of inheritance called complete dominance. 1. Mendel s experiments involved crossing homozygous dominant plants with homozygous recessive plants. In these crosses, only one allele is expressed in the phenotype despite the presence of the other allele. This pattern of inheritance called. K/U 2. Use your knowledge of complete dominance to explain why individuals who are heterozygous and those that are homozygous for the dominant allele can have different genotypes but the same phenotype. T / I A LEARNING TIP Notation of Alleles in Incomplete Dominance In incomplete dominance, alleles are neither dominant nor recessive. In this situation, uppercase letters with superscripts are used to represent different alleles. MAIN IDEA: Not all traits are inherited in simple patterns such as complete dominance. Variations in the patterns of heredity exist, and dominance is not always complete. 3. occurs when neither allele dominates the other and both exercise an influence on the phenotype, resulting in partial expression of both traits. K/U 4. The snapdragon is an organism that displays incomplete dominance for flower colour. Complete Table 1 by recording the flower colour, or phenotype, associated with each genotype. K/U Table 1 Snapdragon Genotypes and Phenotypes Genotype Phenotype C R C R C R C w C w C w 5. Consider a cross between two pink-flowering snapdragons. What percentage T / I of the offspring will have pink flowers? 6. Consider a cross between a red snapdragon and a white snapdragon. What T / I percentage of the offspring will have pink flowers? 20 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 20 1/14/11 8:30:31 PM

21 MAIN IDEA: Codominance occurs when both alleles are fully expressed, producing offspring with a third genotype. 7. Type AB blood is an example of codominance. Draw a Punnett square to show a cross between an individual with type A blood (genotype I A i) and an individual with type B blood (genotype I B i). Circle any offspring that will have type AB blood. T / I A I A i I B I B i i I A i ii MAIN IDEA: Blood type is an example of a gene with multiple alleles. The three blood type alleles are I A, I B, and i. Different combinations of the three alleles produce type A, type B, type AB, and type O blood. 8. (a) Fill in the missing information in Table 2 below to reinforce what you know about human blood types. T / I Table 2 Human Blood Types Genotype Blood type Able to receive blood from Able to donate blood to I A I A A A, AB STUDY TIP Charts and Tables Charts and tables are an effective way to organize information. Create a graphic organizer to differentiate between complete dominance, incomplete dominance, and codominance. I A i A I B I B I B i B I A I B AB ii (b) Which blood type is known as the universal donor? Why? (c) Which blood type is known as the universal recipient? Why? K/U T / I NEL 5.2 Variations in Heredity 21 Bio11SG_U2Ch05_P01.indd 21 1/14/11 8:30:31 PM

22 5.3 Pedigrees Tracking Inheritance Textbook pp Vocabulary pedigree autosomal inheritance sex-linked X-linked Y-linked STUDY TIP Pedigree Chart Symbols You can use a pedigree chart to track the inheritance of traits through generations of a family. With a partner, use fl ashcards to review the symbols used on pedigree charts. MAIN IDEA: A pedigree chart traces the inheritance of a trait among members of a family. It shows the connections between parents and offspring, the sex of individuals in each generation, and the presence or absence of a trait. 1. Use the terms in the box below to label the pedigree symbols below. K/U affected female normal female affected male normal male fraternal twins mating identical twins siblings (a) (c) (e) (g) (b) (d) (f) (h) 2. Draw a pedigree chart for the following: A man and a woman are both heterozygous for a recessive genetic disorder. They have three children: an unaffected female, an unaffected male, and an affected female. The affected female and a man who is heterozygous for the disorder have male fraternal twins who are both affected. T / I A 3. Describe how phenotypes can be used to predict genotypes in a pedigree. MAIN IDEA: The expression of genes on the sex chromosomes differs from the expression of autosomal genes. 4. If an allele is located on an autosome, or a non-sex chromosome, it is transmitted through inheritance. K/U 22 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 22 1/14/11 8:30:31 PM

23 5. In autosomal inheritance, males and females are affected at rates. K/U 6. Identify the two human chromosomes on which an autosomal allele could not be located. K/U 7. Sex-linked inheritance occurs when a allele on the X or Y chromosome of the parent is passed on to the offspring. K/U 8. Red-green colour blindness is an example of X-linked inheritance. A woman who is an unaffected carrier of red-green colour blindness and a man who has normal vision are expecting a child. Draw a Punnett square to show the possible genotypes of their offspring. Use X R to represent the normal allele and X r to represent the allele for red-green colour blindness. T / I X R X r X R X R X R X R X r Y X R Y X r Y 9. Use the information in the completed Punnett square from question 8 to answer the following questions. T / I A (a) In what percentage of male offspring would you expect to have red-green colour blindness? (b) What percentage of female offspring would you expect to be unaffected carriers of red-green colour blindness? (c) How does the expression of the red-green colour blindness trait differ between male offspring and female offspring? 10. Can a male be an unaffected carrier of a recessive X-linked trait? Explain. T / I A NEL 5.3 Pedigrees Tracking Inheritance 23 Bio11SG_U2Ch05_P01.indd 23 1/14/11 8:30:32 PM

24 5.4 Biology Journal: The Gene Hunters Textbook pp STUDY TIP Mind Maps You can use a mind map to organize information found in a reading passage. In this case, the mind map helps collect and organize the main ideas found throughout the reading selection. MAIN IDEA: The gene for Huntington s disease has been located through extensive research. Research continues as scientists seek a way to prevent or cure this disease. 1. Use the mind map below to take notes about Huntington s disease and the search for the Huntington s disease gene. K/U C Symptoms: Tools and Techniques Used in Research: Huntington s disease Mode of Inheritance: Location of Marker: 2. People from all walks of life can make contributions to science. Explain why the hunt for the gene that causes Huntington s disease is an example of this fact. T / I A 3. Scientific inquiry involves questioning, researching, identifying and controlling variables, hypothesizing, predicting, planning, performing and recording, observing, analyzing, evaluating, and communicating. How did Dr. Nancy Wexler s work fit this pattern? Use examples to justify your answer. T / I A 24 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 24 1/14/11 8:30:32 PM

25 Genetic Disorders 5.5 Vocabulary mutation carrier testing genetic screening phenylketonuria (PKU) Textbook pp MAIN IDEA: Many human disorders have a genetic component. 1. A change in the genetic code of an allele is called a. K/U 2. Which of the following disorders is not caused by a gene mutation? K/U (a) Huntington s disease (b) phenylketonuria (c) asthma (d) hemophilia 3. Indicate whether the following statement is true or false. If you think the statement is false, rewrite it to make it true: Cystic fibrosis is passed on through a dominant mutated gene. K/U 4. Complete the Punnett square below to show the possible offspring of an unaffected male carrier of cystic fibrosis and a female with two normal alleles. Use F for the normal allele and f for the cystic fibrosis allele. T / I F F F STUDY TIP Punnett Squares You can use a Punnett square to predict the proportions of genotypes in the offspring resulting from a cross between two individuals. Practise using a Punnett square for various crosses, including the one shown in question 4. f (a) What percentage of the possible offspring do not carry an allele for cystic fibrosis? (b) What percentage of the possible offspring are unaffected carriers of a cystic fibrosis allele? (c) What percentage of the possible offspring will have cystic fibrosis? 5. Would your answers to question 4 differ if the female was a healthy carrier of the cystic fibrosis allele and the male had two normal alleles? Explain your response. T / I A NEL 5.5 Genetic Disorders 25 Bio11SG_U2Ch05_P01.indd 25 1/14/11 8:30:33 PM

26 MAIN IDEA: Genetic screening is used to detect mutated genes that cause genetic disorders. 6. Genetic screening is used to identify the presence of a defective allele that leads to a genetic disorder. Explain how a genetic counsellor might use a pedigree chart in addition to DNA testing in order to diagnose a genetic disorder. T / I 7. Explain how genetic screening can be used to predict the severity of cystic fibrosis symptoms an affected individual will have. T / I 8. Explain how a mutation in BRCA1 or BRCA2 can lead to the development of cancer. T / I A MAIN IDEA: Newborn genetic screening is now used to identify the presence or absence of defective genes in many countries, including Canada. List three specific disorders that are part of Ontario s newborn screening program. K/U 26 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 26 1/14/11 8:30:33 PM

27 Explore an Issue in Genetic Screening 5.6 Textbook pp MAIN IDEA: Genetic testing has many benefi ts, but the use and ownership of the results has raised many ethical and legal issues. 1. Legal access to and ownership of genetic information are topics that will become increasingly important as the ability to test for specific genes and disorders increases. In the chart below, add facts and opinions related to each of the listed questions. When you have completed the chart, you can review the information you have recorded to help you form guidelines about these important issues. C A Question Who makes decisions about access to genetic information? Who should have access to an individual s genetic information? Should an individual ever be required by law to share genetic information? Facts and opinions STUDY TIP Organizing Facts and Opinions for Discussion Charts can be used to organize information related to complex issues. In this chart, you should record your thoughts and opinions about each of the questions listed. Then, you can use this information in group discussions. LEARNING TIP Making Decisions as a Group Before you come to a decision as a group, make a list on chart paper of pros and cons for the question at hand. Place the chart paper where all group members can see and have access to it. This can be helpful in forming new thoughts and ideas about the discussion at hand. During a brainstorming session like this one, take an accepting attitude of all the ideas presented to the group. Wait until the page is full to critique the ideas. NEL 5.6 Explore an Issue in Genetic Screening 27 Bio11SG_U2Ch05_P01.indd 27 1/14/11 8:30:33 PM

28 5.7 Multi-trait Inheritance Textbook pp Vocabulary dihybrid cross law of independent assortment product law discontinuous variation continuous variation additive allele LEARNING TIP Gene Order When completing the Punnett square for a dihybrid cross, keep the genes in alphabetical order and write the dominant alleles (capital letters) fi rst, for example, TtPp. MAIN IDEA: A dihybrid cross involves two traits. 1. A dihybrid cross involves a cross between two individuals who differ in two pairs of. 2. Mendel performed dihybrid crosses in plants that were true-breeding for two traits. For example, a plant that had yellow seed colour and round seed shape was crossed with a plant that had green seed colour and wrinkled pod shape. In this cross, the traits for yellow seed colour (YY) and round pod shape (RR) are dominant. Green seed colour (yy) and wrinkled pod shape (rr) are recessive. T / I C (a) Draw a Punnett square to show the genotypes of the resulting offspring. RY Ry ry ry RY Ry ry RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy ry RrYy RrYy RrYy RrYy (b) If the F 1 generation was then crossed, what would be the resulting genotype ratio of the F 2 generation? 3. Mendel crossed numerous heterozygous F 1 generation plants. What did his experiments reveal to him about the inheritance of traits? Explain your reasoning. T / I STUDY TIP Developing Explanations Diagrams can be used to visualize concepts and ideas. In this case, a Punnett square is used to show how alleles assort independently. Using your completed diagram, explain this concept to a friend. MAIN IDEA: Mendel s law of independent assortment states that alleles of different genes separate into gametes independently of one another. 4. In pea plants, the allele for the trait of tall plants (T) is dominant; the allele for dwarf plants is recessive (t). The allele for purple flowers (P) is dominant; the allele for white flowers (p) is recessive. Complete the Punnett square below (Figure 1) to show the dihybrid cross between two pea plants, both of which are heterozygous for these traits. T / I 28 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 28 1/14/11 8:30:33 PM

29 TP Tp tp tp TP Tp tp tp Figure 1 5. Fill in Table 1 below to show the ratio of the phenotypes of the offspring in the dihybrid cross in question 4. A (a) 9 (b) (c) 3 Table 1 Phenotypic Ratios Number of offspring Phenotype tall plants, white fl owers LEARNING TIP Sample Size Note that Mendel observed these ratios only because of his large sample size. He crossed hundreds of plants, producing thousands of offspring. As sample size increases, the closer the experimental (actual) probability gets to theoretical probability. (d) 6. An individual is heterozygous for two traits. His genotype for those traits is BbGg. In Figure 2 below, show the four possible gametes this individual can produce. T / I A BbGg Figure 2 MAIN IDEA: Genetic ratios are probabilities. 7. The probability of two independent events both occurring may be calculated using the. 8. To calculate the probability of two independent events both occurring, multiply their individual. 9. In a dihybrid cross, either a Punnett square or the probability law can be used to determine the likelihood of a particular outcome. Compare the predicted probabilities using each of these methods. T / I NEL 5.7 Multi-trait Inheritance 29 Bio11SG_U2Ch05_P01.indd 29 1/14/11 8:30:33 PM

30 MAIN IDEA: Variation in the expression of genes can be described as either continuous or discontinuous. 10. variation occurs when a trait is either expressed or is not expressed (i.e. there is no in-between trait). variation occurs in nature when the expression of a characteristic is a sum of the expression of all alleles involved. K/U 11. Classify the pea plant traits studied by Mendel as continuous or discontinuous. Write a sentence to justify your classification. T / I 12. Identify a human trait that exhibits continuous variation. K/U 13. Define the term additive allele. K/U 30 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 30 1/14/11 8:30:34 PM

31 CHAPTER 5 SUMMARY Mendelian Genetics Patterns of Inheritance Gregor Mendel is known as the Father of Genetics because of his study of the inheritance of certain tratis in pea plants. Mendel showed that the inheritance of these traits follows particular laws. law of segregation law of independent assortment based on the conclusions that which states for each characteristic, an organism carries two genes: one from each parent parent organisms donate only one copy of each gene in their gametes. During meiosis, the two copies of each gene separate, or segregate if genes are located on separate chromosomes, they will be inherited independently of one another Punnett squares Patterns of inheritance can be tracked and predicted using tools such as include pedigree charts complete dominance incomplete dominance codominance which occurs when which occurs when which occurs when one allele determines the phenotype, regardless of the presence of another allele neither allele dominates the other; both exercise an influence on the individual, resulting in partial expression of both traits both alleles are expressed fully, resulting in offspring with a third phenotype NEL Chapter 5 Summary 31 Bio11SG_U2Ch05_P01.indd 31 1/14/11 8:30:34 PM

32 CHAPTER 5 QUESTIONS K/U Knowledge/Understanding T / I Thinking/Investigation C Communication A Application For each question, select the best answer from the four alternatives. 1. Which of the following statements is one of the conclusions that forms the law of segregation? (5.1) K/U (a) Each parent passes on only one of its two alleles for each gene. (b) Dominant alleles, if present, are always passed on. (c) The frequency of genotypes among offspring is random and cannot be predicted. (d) Individuals have a single, segregated allele for each gene. 2. An individual with the genotype I A i has type A blood. What do this particular genotype and phenotype demonstrate? (5.2) K/U (a) compatible dominance (b) codominance (c) complete dominance (d) incomplete dominance Indicate whether each of the statements is true or false. If you think the statement is false, rewrite it to make it true. 3. A diagram used to show the inheritance of a trait through generations of a family is called a Punnett square. (5.3) K/U 4. Nancy Wexler is a scientist who investigated the cause of phenylketonuria. (5.4) K/U Respond to each statement or answer each question below. 5. An individual with type AB blood marries an individual with type O blood. Is it possible for their offspring to have the same blood type as either parent? Explain your response. (5.2) T / I A 6. Describe the symptoms of cystic fibrosis. Then, classify the allele that causes the disorder as dominant or recessive and state whether it is autosomal or X-linked. (5.5) K/U T / I 7. Identify one ethical issue related to genetic screening. Then, write a sentence that summarizes your opinion on this issue. (5.6) T / I A 32 Unit 2 Genetic Processes NEL Bio11SG_U2Ch05_P01.indd 32 1/14/11 8:30:34 PM

33 8. Compare and contrast discontinuous and continuous variation. Identify one way they are similar and one way they are different. (5.7) T / I 9. In humans, the allele M codes for melanin, and the allele m does not. Individuals with the genotype mm have albinism. Draw a Punnett square to show a cross between two individuals who are heterozygous for this trait and circle any possible offspring who will have albinism. (5.1) T / I C M m M MM Mm m Mm mm 10. Fill in Table 1 below to compare codominance, complete dominance, and incomplete dominance. (5.2) T / I C Table 1 Number of alleles present Codominance Complete dominance Incomplete dominance Number of alleles that affect phenotype Phenotype of heterozygote 11. Draw a pedigree chart to show the following: A man with an autosomal recessive disorder and a woman who does not carry the allele for this disorder have three children: a son, a daughter, and another son. None of the children have the disorder. The youngest son and a woman who is an unaffected carrier of this disorder have two daughters. Both of their daughters have the disorder. (5.3) T / I C A I 1 2 II III 5 6 NEL Chapter 5 Questions 33 Bio11SG_U2Ch05_P01.indd 33 1/14/11 8:30:34 PM

34 DNA and the Code of Life 6.1 Vocabulary nuclein X-ray crystallography scientifi c model complementary base pairing nucleotide Textbook pp MAIN IDEA: Many scientists have contributed to the discovery of deoxyribonucleic acid (DNA) as the molecule that stores and transmits genetic information from parent(s) to offspring. 1. Fill in Table 1 to keep track of the experiments discussed in this section. Explain how each experiment contributed to the discovery of DNA as genetic material. K/U Table 1 Scientist Miesher Contribution (a) Hammerling (b) Hershey and Chase (c) Levene (d) Watson and Crick (e) 2. What evidence was there that genetic material is contained in the nucleus? 3. How did Hershey and Chase prove that DNA was hereditary material? T/I NEL 6.1 DNA and the Code of Life 1 Bio11SG_U2Ch06_P01.indd 1 1/14/11 8:55:37 PM

35 STUDY TIP Diagrams You can use diagrams to learn about the structure of biological molecules. Start a visual glossary for terms in this chapter that can be diagrammed. For each, write the term and draw a diagram. At the end of the chapter, use your visual glossary for review. LEARNING TIP DNA Twist DNA exists as a right-handed double helix as a well as a left-handed double helix. The two types of helix are mirror images of each other. Watson and Crick built a model of a right-handed helix. MAIN IDEA: DNA is composed of four types of nucleotides. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. 4. Figure 1 below shows a nucleotide. Label the following components: deoxyribose sugar, nitrogenous base, and phosphate group K/U (a) O O P O Figure 1 O (b) (c) CH 2 OH O HC CH OH O HN H C CH O C N CH C CH CH 3 5. What is the only difference among the four nucleotides? K/U 6. List the four possible nitrogenous bases that are found in the nucleotides of DNA. K/U 7. Describe the relationship among the nitrogenous bases in DNA that was discovered by Chargaff. K/U MAIN IDEA: James Watson and Francis Crick determined the structure of the DNA molecule. 8. DNA consists of strands that run in directions. Each strand is made up of alternating and molecules with nitrogenous bases attached to the backbone. 9. Define the term X-ray crystallography, and describe the role this technique played in the development of Watson and Crick s model of DNA structure. T/I C 2 Unit 2 Genetic Processes NEL Bio11SG_U2Ch06_P01.indd 2 1/14/11 8:55:38 PM

36 10. Identify at least one discovery by other scientists that Watson and Crick accounted for when developing their own model of DNA. T/I MAIN IDEA: Nucleotides always pair in the same way. 11. Define the term complementary base pairing. K/U 12. Identify the complementary base pairs in DNA. K/U 13. The sequence of a piece of DNA is GATCTCGA. What is the complementary base sequence? T/I A NEL 6.1 DNA and the Code of Life 3 Bio11SG_U2Ch06_P01.indd 3 1/14/11 8:55:38 PM

37 6.2 Mutations Textbook pp Vocabulary point mutation chromosome mutation spontaneous mutation induced mutation antibiotic resistant transposon transposition microarray MAIN IDEA: A mutation is a change in the genetic code of an allele. Some mutations affect sequences of DNA in a gene, whereas others affect an entire chromosome. 1. Compare and contrast point mutations and chromosomal mutations. T/I 2. (a) In Table 1, describe what happens in each type of point mutation. K/U Table 1 Point Mutations Type of point mutation Description base-pair substitution insertion deletion (b) What are the similarities and differences among the three types of point mutations? T/I 3. A sequence of DNA is shown below. Show how each of the following types of mutations would affect the sequence by rewriting a sequence to include the mutation. For each answer, use an arrow to point out the mutation. T/I A (a) Base-pair substitution: G C G T T A C G G C (b) Insertion: (c) Deletion: 4 Unit 2 Genetic Processes NEL Bio11SG_U2Ch06_P01.indd 4 1/14/11 8:55:38 PM

38 4. All the mutations you modelled in Question 3 changed the sequence of bases read by ribosomes in the cell. What is the effect of changing the DNA sequence that the ribosomes read? T/I 5. Why aren t mutations in body cells passed on to offspring? T/I A MAIN IDEA: Mutations are caused by several factors. 6. A mutation that occurs randomly and is not due to any outside factors is called a(n) mutation. K/U 7. A mutation that is the result of exposure to a physical or chemical agent is called a(n) mutation. K/U 8. What are two chemical or physical factors that can cause mutations? K/U MAIN IDEA: Mutations can be helpful, harmful, or have no effect on organisms. 9. Explain why lactose tolerance can be described as a beneficial mutation. T/I 10. Identify a factor that can cause the proportion of lactose tolerant and intolerant individuals in a population to vary from one location to another. T/I MAIN IDEA: Bacteria have developed antibiotic resistance due to mutations, including those in the gene that directs the shapes of cell wall building-block molecules. 11. Explain why a mutation that affects a bacterium s cell wall structure might confer antibiotic resistance to the bacterium. T/I STUDY TIP Main Idea Webs You can use a main idea web to organize facts about a topic. After you have completed the main idea web for question 12, choose another topic in the chapter, and create another main idea web for that topic. NEL 6.2 Mutations 5 Bio11SG_U2Ch06_P01.indd 5 1/14/11 8:55:38 PM