EOC Review Reporting Category 2 Mechanisms of Genetics

Transcription

1 EOC Review Reporting Category 2 Mechanisms of Genetics The student will demonstrate an understanding of the mechanisms of genetics. Langham Creek High School By PresenterMedia.com

2 TEK 6A Identify the components of DNA, and describe how information specifying the traits of an organism is carried in the DNA. DNA DNA stands for Deoxyribonucleic acid DNA is the master copy of an organism s genetic information. The information in DNA contains instructions used to form nearly all of an organism s proteins. DNA is the blueprint for how an organism works and how it looks. For example, DNA determines eye color, body structure, and enzyme production. DNA is passed on every time a cell divides. The DNA in all of your cells is the same. DNA is also passed from one generation of an organism to the next.

3 DNA Nucleic acids are made of smaller subunits (monomers) called nucleotides. A nucleotide is made of a sugar, a phosphate, and a nitrogen base. In DNA, nucleotides form two long chains that form a double helix (like a winding staircase). The backbone of the double helix is made up of sugar molecules and phosphate groups, and the two chains are joined together by hydrogen bonds between the nitrogen bases. The two bases that form each rung of the ladder are called a base pair. In DNA, cytosine and guanine form one base pair; thymine and adenine form the other base pair. TEK 6A Identify the components of DNA, and describe how information specifying the traits of an organism is carried in the DNA.

4 DNA The order of the nitrogen bases determines everything about every organism because it tells our cells how to make proteins. A protein is made up of amino acids. How your body puts amino acids together determines how you look and how you work. DNA controls eye color and eye shape, hair color and texture, and your other traits by controlling how your proteins are put together. TEK 6A Identify the components of DNA, and describe how information specifying the traits of an organism is carried in the DNA.

5 Talk to your neighbor. DNA If a DNA sequence is ACG TCA GCA CTG what would the complementary base pair be? TGC AGT CGT GAC Explain the role DNA plays in gene expression (traits). TEK 6A Identify the components of DNA, and describe how information specifying the traits of an organism is carried in the DNA.

6 Changes in DNA A section of DNA on a chromosome that directs the making of a specific protein is called a gene. Genes control the traits inherited by an organism. If a change occurs in the sequence of nitrogen bases, the trait may be changed. Any permanent change in the sequence of nucleotides is called a mutation. Some mutations, like flower color in plants, are not harmful, but some mutations can cause disease. Although many mutations are harmful, they also add genetic diversity to a species. TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

7 Changes in DNA Any change in DNA or RNA can change which proteins are made, which can change how our cells look and how our cells function. Point Mutations Substitution mutation - a different nucleotide replaces one that was originally present Insertion mutation - a base is added Deletion mutation - a base is deleted TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

8 Frame Shift Mutations Changes in DNA Inserting or deleting one or more nucleotides Changes the reading frame like changing a sentence Proteins built incorrectly Example Original: The fat cat ate the wee rat. Frame Shift ( a added): The fat caa tet hew eer at. TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

9 Changes in DNA Mutations can also occur at the chromosomal level. Chromosomal Level Mutations Inversion - Chromosome segment breaks off, Segment flips around backwards, Segment reattaches Deletion -Due to breakage a piece of a chromosome is lost Inversion TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

10 Changes in DNA Chromosomal Level Mutations, cont. Duplication - a gene sequence is repeated Translocation involves two chromosomes where part of one chromosome is transferred to another chromosome TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

11 Changes in DNA Chromosomal Level Mutations, cont. Non-Disjunction - Failure of chromosomes to separate during meiosis this causes gametes to have too many or too few chromosomes. One form is trisomy 21 (Down s Syndrome). TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

12 Changes in DNA Mutations are usually random events. Some mutations are caused by mutagens, substances in the environment like ultraviolet light, X rays, radioactive substances, cigarette smoke, and pollutants. If mutations occur in body (somatic) cells, they can cause cancer. Only changes in gametes (eggs and sperm) are passed on to offspring. TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

13 Talk to your neighbor Changes in DNA Find the amino acid sequence for the following DNA AAG GTA CTA GCA CGA AAA TAG How would the amino acid sequence change if the following mutation occur? AAG GTA ATA GCA CGA AAA TAG What kind of mutation is this? TEK 6E Identify and evaluate changes in DNA and evaluate the significance of these changes.

14 Heredity Traits are inherited from one generation to the next. Each person inherits half of their chromosomes from their mother and half of their chromosomes from their father. Genes- sections of DNA on a chromosome that control traits. There are different forms of each gene called alleles. For example, a gene for flower color may code for white flowers (one version/ allele) or red flowers (another version/ allele). TEK 6F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance.

15 Heredity Homozygous- the two alleles for a trait are the same Ex. If a plant inherits two copies of the red allele (RR) If a plant inherits two copies of the white allele (rr) Heterozygous- the two alleles for a trait are different Ex. If a plant inherits one copy of the red allele and one copy of the white allele (Rr) Genotype- the gene combination that an organism contains Phenotype- the way an organism looks Dominant the allele that shows its self if present Recessive must have 2 identical alleles for this trait to appear TEK 6F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance.

16 Heredity Punnett Squares are devices used to find out the possible offspring of a cross. For example In mice, black fur is dominant to white fur. If two heterozygous individuals (Bb) are crossed: 75% of the offspring are likely to be black. (BB or Bb) 25% of the offspring are likely to be white. (bb) TEK 6F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance.

17 Heredity Dihybrid cross - examines the inheritance of two traits. Follows the same basic rules as a simple punnett square. When setting up a dihybrid cross, you must first determine all possible gametes that each parent can contribute. Ex. In pea plants, round is dominant to wrinkled and yellow is dominant to green. Crossing two heterozygous individuals will yield a 9:3:3:1 phenotypic ratio. RrYy x RrYy 9 yellow and round 3 yellow and wrinkled 3 green and round 1 green and wrinkled TEK 6F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance.

18 Heredity Non-Mendalian Genetics Some traits don t follow the simple dominant / recessive rules that Mendel first applied to genetics. Traits can be controlled by more than one gene. Some alleles are neither dominant nor recessive. Incomplete Dominance - One allele is not completely dominant over another. The heterozygous phenotype is a blending of the two homozygous phenotypes. Example: four o clock flowers rr=red ww=white rw=pink (blending of the two alleles) TEK 6F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance.

19 Heredity Non-Mendalian Genetics, cont. Codominance - Two alleles are both expressed as a dominant phenotype Ex. Coat color in cows RR: Red WW: White RW: Roan, white with red spots (NOT pink!) Sex Linked traits are associated with gender, generally attached to the X chromosome. Ex. Hemophilia or Color blindness. TEK 6F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance.

20 Talk to your neighbor Heredity Use a punnett square to cross a light eyed individual with an individual who is heterozygous for eye color. Show the genotypic and phenotypic ratios. Use the table to create the dihybrid cross shown below. BE sure to show the genotypic and phenotypic ratios. A woman who is homozygous for normal blood clotting marries a man who has hemophilia. What are the chances of them having a son or daughter with hemophilia? TEK 6F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance.

21 Meiosis Meiosis is a special kind of cell division that produces gametes (sperm and egg) that have only half the number of chromosomes as the parent cell. Your body is made of somatic cells that each has 46 chromosomes. Of the 46 chromosomes in each of your body cells, 23 came from one of your parents, and 23 came from the other parent. The two sets of matching chromosomes are called homologous chromosomes. A cell (like a somatic cell) that contains both sets of homologous chromosomes is said to be diploid. The number of chromosomes in a diploid cell is represented by 2n. (For example, in humans 2n= 46. The body cells of a fruit fly each contain 8 chromosomes, which is written as 2n= 8.) TEK 6G Recognize the significance of meiosis to sexual reproduction.

22 Meiosis Meiosis results in cells that have half the number of chromosomes of the parent cell. The cells are called haploid cells, and they are represented by 1n. So 1n = 23 for humans. At the end of meiosis, four genetically diverse, haploid gametes are produced. TEK 6G Recognize the significance of meiosis to sexual reproduction.