Why Pea Plants? Mendel chose to study garden peas, because: 1. They reproduce & have a short life cycle 1

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1 Name: Date: Per: Genetic Notes Genetics Genetics Vocab Identify the definitions and/or vocabulary words below. You will need to know these terms moving forward! 1. P Generation 2. Hybrid (F1) Generation 3. F2 Generation 4. Monohybrid Cross 5. Dihybrid Cross 6. Punnett Square 7. Dominant (allele) 8. Recessive (allele) 9. Genotype 10. Phenotype Gregor Mendel The scientific study of heredity is called! Who was Gregor Mendel? - Austrian Monk - Worked with in his monastery Correctly believed that factors ( ) retain their from generation to generation - EXAMPLE marbles in a bag Why Pea Plants? Mendel chose to study garden peas, because: 1. They reproduce & have a short life cycle 1

2 2. They have seven distinct & traits 3. They produce offspring in one cross 4. Ease in manipulating (because they -fertilize AND cross pollinate) Mendel s Experiments After studying, Mendel concluded that: - Traits are passed from one generation to the next through - Each trait is controlled by a different form of a gene called an - Some alleles are to others called recessive traits Question: Have the recessive alleles disappeared or are they still present in the parents? What does A represent? A. Sex Cell B. Allele C. Trait D. Both B and C Mendelian Inheritance o Three types of Mendelian Patterns of Inheritance 1. Dominance 2. Law of 3. Law of Assortment What is Complete Dominance? o Recessive alleles will always be by dominant alleles - will show a dominant trait - will show a recessive trait o two identical alleles for a trait AA homozygous aa homozygous o two different alleles for a trait - Aa one of each allele Law of Independent Assortment Mendel used pea plants to see patterns in the way various traits were inherited Using his data, he saw that when two or more characteristics are inherited, individual factors assort independently during gamete production - giving different traits an equal opportunity of occurring together - Example: Green pea color isn t always inherited with wrinkled pea shape.green peas can be smooth and round too! - Example #1 blonde hair isn t always with blue eyes - Example #2 peas can be green and wrinkled OR green and round 2

3 - This idea is called the Law of Independent Assortment! This explains genetic among organisms Law of Segregation o Alleles (separate) from each other during the formation of gametes. o Occurs during in o separate à the gametes carry one allele and the other half carry the allele. o Ex: each offspring will acquire one allele from each parent. o Evidence: Mendel crossed the first generation and saw that the recessive trait showed up in about of plants. Practice Problem #1 A) A purebred purple flower mates with a purebred white flower and they have all purple flower babies. If two of the purple flower babies cross and have a mixture of both purple and white flowers, what color/trait can we say is RECESSIVE? WHY? B) What would the GENOTYPE be for the recessive flower? C) What flower color is DOMINANT? D) What would the GENOTYPE be for the dominant flower color in the P generation? Punnet Squares! What is a Punnett Square? Way to predict ALL outcomes of a cross How do you read a Punnett square? Axes represent possible gametes from each parent Boxes represent possible genotypes for offspring What is a monohybrid cross? Crosses to show inheritance of only specific Example: Crossing a homozygous dominant TALL parent with a homozygous recessive SHORT parent. ONLY crossing for the height trait Monohybrid Ratios Genotype Ratio should be broken down by genotype(s) and number(s) # TT : # Tt : # tt 0 TT : 4 Tt: 0 tt à so, we say Tt Phenotype Ratio should be broken down by physical description(s) and number(s) # Tall : # Short 3

4 4 Tall: 0 Short à so we say 100% Punnett Square Problems Practice #1 If a homozygous round pea plant is crossed with a heterozygous round pea Step 1 - Define the After reading the problem, create a key, in which you will define the alleles For example for the problem If a homozygous round pea plant is crossed with a heterozygous round pea plant, what will their offspring look like? on your paper, you should write: Key: R = round à = Step 2 Define the The parents will be x Step 3 Draw the Punnett square with the parent genotypes on top (RR) and across (Rr) Step 4 plant, what will their offspring look like? Cross the parents to find the probability of offspring by bringing the top letter down and the side letter over Step 5 Find the genotype and the phenotype of the offspring. Genotype: (letters) Phenotype: physical Finished Product! Your finished punnett square should look like this. Key: R = r = R R RR R RR Genotype: 2 : 2 Phenotype: 100% Practice #2 r Rr Rr 4

5 Yellow seeds are dominant to green seeds in peas. Show a cross between a homozygous yellow seed and homozygous green seed. Key: Y = y = Cross: Genotype: Phenotype: Practice #3 In pea plants, round seeds are dominant over wrinkled. A plant that is heterozygous for round seeds is crossed with another heterozygous plant. Hint: Use the letter R for your key! Key: = = Cross: Genotype: Phenotype: Dihybrid Punnett Squares! What is a Dihybrid Cross? A cross that shows inheritance of traits For example: homozygous round & yellow crossed with a heterozygous round & yellow seed - Homozygous round and yellow - RRYY - Homozygous wrinkled and green - RrYy Setting up a Dihybrid Step #1 Read the problem & list all 4 For example: - R = round - Y = yellow - r = wrinkled - y = green Step #2 Create the parental genotypes (each will be 4 letters) Example: (Round, Yellow) x (wrinkled, green) Step #3 Using the foil method, à First, Outer, Inner, Last à determine the sets of gametes (up to 4 possibilities) Example: 1. RRYY à 5

6 2. RrYy à,,, Step #4 Fill in the tops and sides of punnett square with gamete combinations Example: RY RY Ry ry ry Step #5 Genotype and Phenotype as usual (remember the key!) Example: - RRYY = - RRYy = Round and yellow - RrYY = KEY: R = round r = wrinkled Y = yellow y = green - RrYy = Round and yellow - So we can say ALL the offspring ( ) will be and yellow! Dihybrid Genotype Naming Practice In rabbits, grey hair (G) is dominant to white hair. Also, black eyes (B) are dominant to red eyes. What are the phenotypes of rabbits that have the following genotypes: - Ggbb: - ggbb: - ggbb: - GgBb: Dihybrid Example Problem #1 Round is dominant over wrinkled Yellow is dominant over green Two pea plants produce offspring. One is round and heterozygous for yellow seed color. The other is wrinkled and heterozygous for yellow seed color. Step 1 Determine the parental genotypes = X Determine the possible gametes! Step 2 Set up the dihybrid cross using the gametes from before 6

7 Step 3 Determine the genotype and phenotype! Genotype: 1 : 2 :: 1 Phenotype: Dihybrid Example Problem #2 Black fur (B) is dominant to white fur Long hair (L) is dominant to short hair Two guinea pigs mate. The dad is homozygous for black fur and long hair. The mom is also homozygous, but for white fur and short hair. 1) Determine the parental traits 2) Determine the possible gametes of each parent 3) What is the only genotype possibility for their offspring? Dihybrid Example Problem #2 SOLUTION 1) DAD = MOM = 2) Determine the possible gametes of each: DAD à MOM à 3) What is the only genotype possibility for their offspring? GENOTYPE: PHENOTYPE: Dihybrid Example Problem #3 o Find the possible gametes and offspring phenotype possibilities if a black lab (EEBB) mates with a chocolate lab (EEBb). Phenotypes: Pedigrees A pedigree is a that traces specific across many 7

8 Pedigrees help us determine whether alleles are or. How do you create a pedigree? - Collect information about a family s history - Organize the information in a family tree - Apply Mendel s concepts and principles Offspring are drawn below the parents Pedigree Basics: Male = Square Female = Circle Horizontal Line = Marriage Dotted line = adoption By coloring in the shapes you are indicating an trait/phenotype Other pedigree symbols Identical Twins = Incest Marriage = Fraternal Twins = Death = Pedigrees can help us determine if a trait is: 1. Dominant or 2. (passed on or chromosome) OR passed on chromosomes ) What would a dominant trait look like in a pedigree? o It will show up in generation. o How do you know? What would a recessive trait look like in a pedigree? It will be in generation. Why???? 8

9 Let s Practice! 1. Are freckles dominant or recessive? 2. What genotype MUST II-4 and II-5 have? 3. What about III-4? 4. What about III-10???? Non-Mendelian Inheritance Five types of non-mendelian Patterns of Inheritance o Sex-linked inheritance o Incomplete Dominance o Codominance o Multiple Alleles o Polygenic Sex Linked Heredity How is Gender Determined? ALWAYS give an X CHROMOSOME Male can give either an or a What is the probability of having a boy baby? What is the probability of having a girl baby? What is a Sex-linked gene? Any gene that resides on a sex chromosome Y- linked: Only will express the trait X-linked: Females AND males will the trait Colorblindness (recessive) Hemophilia (recessive) Is there a bias for one gender to be more affected by an X-linked gene than the other? WHICH & WHY? 9

10 What is a Sex-Linked gene? o In an X a Y the "a" recessive allele will in his phenotype o In an X a X A the "a" recessive allele will be in her phenotype o Sex linked genes can be on either the X or Y chromosome o Genes on the X chromosome can be passed to either sons or daughters. o **Genes on the Y chromosome can only be passed to sons! NOT to daughters** o Females can be: - Homozygous affected à - Homozygous unaffected à - Heterozygous carriers à o Males will be: - Affected à - Unaffected à Colorblindness o Red-green colorblindness is caused by cells (cones) in the eyes that aren t working properly o Individuals who are affected can t distinguish from o Usually inherited as traits - Males only need to inherit recessive allele to have disorder (X a Y) - Females must inherit recessive alleles to have the disorder à 1 allele from mother and 1 allele from father (X a X a ) Sex-Linked Practice Problems #1 Hemophilia is a sex-linked gene carried on the X Chromosome. Let s practice phenotypes possibilities for sexlinked individuals! List all possible outcomes for hemophilia: - X H X H à - X h X h à - X H X h à - X H Y à - X h Y à Sex-Linked Practice Problems #2 Cross a regular female and a hemophilic male. Identify the phenotypic values for each gender. Parent Cross: Genotypic Ratio: Phenotypic Ratio: girls will be for hemophilia and of boys will hemophilia 10

Sex-Linked Practice Problems #3 A woman who is a carrier for colorblindness (but has normal vision) mates with a man that is colorblind. Create a key to identify all possible genotypes.

11 Sex-Linked Practice Problems #3 A woman who is a carrier for colorblindness (but has normal vision) mates with a man that is colorblind. Create a key to identify all possible genotypes. B = normal color-seeing allele b = colorblind allele X B X B = normal female = carrier female = affected female = normal male = hemophiliac male Using your key, complete a punnett square to identify their possible offspring. Genotypic Ratio: Phenotypic Ratio BY GENDER: Sex-Linked Practice Problems #4 A carrier female marries a normal male. What are the chances that they will have a hemophiliac child? Key: H = normal healthy allele h = hemophilia allele Phenotypic Ratio: X H X H = normal = carrier female X H Y = normal = hemophiliac male 1 daughter 1 daughter 1 son 1 son % they ll have a child with hemophilia? Colorblindness through Pedigrees o Colorblindness is passed along on the X Chromosome (just like hemophilia) o Using the pedigree (right), what is the genotype of II-2? 11

12 Incomplete Dominance & Codominance What is Complete Dominance? Organism only needs one dominant allele to obtain the dominant genotype Both in the homozygous (DD) or heterozygous (DD) state What is Incomplete Dominance? Incomplete Dominance type of when the phenotype is a mixture of the two phenotypes o Neither allele is completely dominant or recessive o NOT blending Example: Green beta fish (C G C G ) Blue beta fish (C B C B ) Teal beta fish (C G C B ) C B C B x C G C G = teal beta fish Incomplete Dominance Problem #1 If a red four o clock flower is crossed with a pink four o clock flower what will their offspring look like? C R C R = red C W C W = white = pink Cross: Genotype Ratio: Phenotype Ratio: Incomplete Dominance Problem #2 In the four-o clock plant, homozygous shows the red flower color and homozygous shows the white flower color. Cross a red plant with a white plant and list the genotypic and phenotypic ratios. Cross: Genotype Ratio: Phenotype Ratio: 12

13 What is Codominance? When both the dominant and recessive trait is expressed allele is dominant or recessive Example: A flower that is homozygous for red flowers (RR) is crossed with a plant that is homozygous for blue color (BB). The offspring (RB) will have spots of blue and spots of red but NO purple - x = blue and red spotted (RB) - ***NOTE: the letters are ALWAYS CAPITAL!*** Codominance Example In cattle, fur color can either be red (C R C R ), white (C w C w ) or roan (C R C w ). Example: Roan fur is both red hairs and white hairs together Codominance Example #1 Black feathers and white feathers in chickens are codominant. In the heterozygous condition the feathers are called erminette and appear blue. C B C B = C W C W = C B C W = Parents Cross: Genotype Ratio: Phenotype Ratio: Codominance Example #2 Roan is a coat color found in some cows = red hair = red and white hair (Roan) = white hair Parents Cross: Genotype Ratio: Phenotype Ratio: Multiple Alleles & Codominance Most genes can be found in more than 2 forms à Example à blood types There are 3 alleles (, B and ) We write the alleles: 1. = 2. = 3. = When combined, they create 4 blood phenotypes:, B,, and 13

14 Each parent gives us allele Because there are 3 alleles, there are total combination possibilities - Fill in the following table as a helpful guide.! Phenotype Genotype Can Receive Blood From A B AB O Blood Type Key in Detail A Blood Type Type A à I A I A Heterozygous Type A à I A i B Blood Type Type B à I B I B Type B à I B i AB Blood Type ( ) I A I B AB is the universal receiver O Blood Type ( ) ii O is the universal donor Rh and Antigens Antigens are protein markers on the surface of cells that help the immune system identify a foreign cell/virus A and B are antigens that are on the surface of red blood cells People have one, both, or none If you don't naturally produce the antigen, your body's white blood cells will attack and destroy red blood cells that carry them Examples: ² A person with AB+ blood is a universal receiver, because they already produce all of the normal antigens present on red blood cells ² A person with O- is a universal donor, because it lacks all antigens à no one's body will recognize it as foreign Rh Factor Rh factor is another protein People are either Rh+ (have protein) or Rh- (do not have protein) If you are Rh- and receive Rh+ blood, immune system makes proteins that cause blood cells to SWELL = BURST 14

15 Thus, when getting blood, both the blood type and Rh factor must be matched!!! Practice Problem #1: #1) A type AB woman marries a type O man. What are the possible genotypes of their offspring? Phenotype: Genotype: Phenotypic Ratio: Genotypic Ratio: Practice Problem #2: Papa Whittaker is convinced his blood type is AB-. Mama Whittaker has given blood many, many times and knows that she is O+. Ms. Whittaker has also given blood and is A+. Emily Whittaker is O+, just like Mama Whittaker. A) What is the genotype of II-3? B) What are the possible genotypes and phenotypes for Shannon Whittaker? Explain! C) Is it possible for Papa Whittaker to be AB-? Explain Polygenic Traits A trait is determined by genes Results in a wide range of phenotypes Example: Skin color, eye color, hair color. Challenge Problem: Key: Capital M = Melanin, darker skin color Capital N = No Melanin, lighter skin color Imagine the following couple: NN NN NN (female) x NN MN NN (male) 1. Give the phenotypes for each parents. Female: Male: 2. What is the genotype of the darkest child they could have? 3. What are the odds of producing such a child? Show your math: 4. What is the genotype of the lightest child they could have? 5. What are the odds of producing such a child? What are the odds of having a child that is heterozygous for all three genes? 15

Non Mendelian Genetics

Non Mendelian Genetics TEKS 6 Science concepts. The student knows the mechanisms of genetics, including the role of nucleic acids and the principles of Mendelian Genetics. The student is expected to: 6F