1. Welcome to Genetics: Unit 2 Seminar! Please feel free to chat with your classmates! 1

2. Agenda Brief Review Genetics Problem –#1, #2, 2.3, 2.5 and 3.1 Question 2

3. Alleles Alleles are pairs of genes that carry the same traits and are found at the same locations on pairs of chromosomes. From MotherFrom Father 3

4. Dominant – only one allele of a gene necessary to express the trait Recessive – both alleles of a gene must be identical to express that trait Autosomal Inheritance GENES 4

5. Genetic Terms Homozygous Trait - Both genes for that trait are the same.  A pea plant with two genes for tallness. Heterozygous Trait - Both genes for that trait are not the same.  A pea plant with one gene for tallness and one for shortness. 5

6. Human Molecular Genetics Homozygous - a diploid cell or organism carry two identical copies of a gene Heterozygous - a diploid cell or organism having two different alleles of a particular gene heterozygous homozygous 25%75% 6

7. Human Molecular Genetics Genotype – entire genetic constitution of an individual cell or organism, usually with emphasis on the particular alleles at one or more specific loci. Phenotype – the detectable physical and physiological characteristics of a cell or organism determined by its genotype; also, the specific trait associated with a particular allele. GENES 7

8. Practice Problem 1 Beak color is an autosomal trait in chickens. Red beaks are dominant over white beaks. The allele for red beaks is R. The allele for white beaks is r. 8

9. ClaudeFilette Practice Problem 1 Claude is a chicken that has a red beak and has a genotype of Rr. If this chicken mates with a white-beaked chicken named Filette, what will the baby chickens look like? What would be their phenotypes and genotypes? Rrrr 9

10. Claude Filette Practice Problem 1 Rr rr X ? What is their Genotype? What is their Phenotype? 10

11. Claude Filette Practice Problem 1 Rr rr X 50%50% Genotype is rr Phenotype is white beak Genotype is Rr Phenotype is white beak 11

12. Practice Problem 2 John is homozygous dominant for the T allele decides to have children with a Jane who is homozygous recessive. We will say the T allele is a Tall gene: T = tall t = short *Note: In reality, there is no tall gene. 12

13. Practice Problem 2 John is homozygous dominant for the T allele decides to have children with a Jane who is homozygous recessive. First what is John and Jane’s genotypes? John Jane 13

14. Practice Problem 2 John is homozygous dominant for the T allele decides to have children with a Jane who is homozygous recessive. First what is John and Jane’s genotypes? JohnTT Janett 14

15. Practice Problem 2 JohnTT Janett X What will their children be like? Again, include the children's genotypes and phenotypes. 15

16. John Junior Tt Jane Junior Tt Practice Problem 2 John and Jane’s Children Both are tall 16

17. Discussion Question 2.3 A woman is affected with a trait due to a dominant gene that shows 50% penetrance. What is the probability that, if she has a child, it will be affected? 17

18. 18 Incomplete Dominance Incomplete dominance = the phenotype of the heterozygous genotype is intermediate between the phenotypes of the homozygous genotypes Incomplete dominance is often observed when the phenotype is quantitative rather than discrete

19. Discussion Question 2.5 With independent assortment, how many different types of gametes are possible from the genotype K/k; L/l; M/m; P/p and in what proportions are they expected? 19

20. Discussion Question 2.5 With independent assortment, how many different types of gametes are possible from the genotype K/k; L/l; M/m; P/p and in what proportions are they expected? Gametes – egg or sperm. Each gene has two possible alleles; K or k. Therefore, the number of possible types of gametes are 2 X 2 X 2 X 2 = 16 The occur at an equal frequency. 20

21. Discussion Question 3.1 A somatic cell has 32 chromosomes aligned at metaphase. How many chromosomes are present at anaphase immediately after the centromeres have splits? 21

22. 22 Fig. 3.3 Mitosis

23. Questions? 23