Homework p. 148 q. 2

1. Homework p. 148 q. 2 Guinea pigs with a yellow coat colour have the genotype CYCY. Guinea pigs with cream coat colour (cream-coloured hair) have the genotype CYCW, and those with white coat colour have the genotype CWCW. Is the condition for coat colour one of complete dominance, incomplete dominance or codominance? Explain.

2. Homework p. 148 q. 2 The condition for guinea pig coat colour is one of incomplete dominance. The heterozygous coat colour is a blend of yellow and white. Complete dominance would result in either a yellow coat or a white coat. Codominance would result in individual hairs that are either yellow or white.

3. Homework p. 148 q. 3 Phenylketonuria is a genetic disorder caused by a dominant allele. People with PKU are unable to metabolize an .. amino acid, phenylalanine. If [it] accumulates, it inhibits the development of the nervous system, leading to mental retardation. The symptoms of PKU are not usually evident at birth but can develop quickly if the child is not put on a special diet. Figure 5 is a pedigree chart that shows the inheritance of the defective PKU allele in one family.

4. Homework p. 148 q. 3 I • How many generations are shown on the pedigree chart? There are three generations shown on the pedigree chart. • How many children were born to the parents of the 1st generation? There were five children born. II III

5. Homework p. 148 q. 3 I c. What are the genotypes of individuals 1 and 2 in generation I? The female is heterozygous. The male is homozygous recessive d. How is it possible that in generation II, some of the children showed symptoms of PKU while others did not? The mother has a heterozygous genotype. Homozygous recessive children can be produced when she mates with a homozygous recessive male. II III

6. Homework p. 149 q. 4 Multiple alleles control the intensity of pigment in mice. The gene D1 designates full colour, D2 designates dilute colour, and D3 is deadly when homozygous. When a full coloured male is mated to a dilute-coloured female, the offspring are produced in the following ratio: two full colour to one dilute to one dead. Indicate the genotypes of the parents.

7. Homework p. 149 q. 4 D2 D3 Phenotypic Ratios Full(2):Dilute(1):Dead(1) 50% Full Colour 25% Dilute Colour 25% Dead D1 D1D3 D1D2 D3 D2D3 D3D3

8. Homework p. 149 q. 5 Multiple alleles control the coat colour of rabbits. A grey colour is produced by the dominant allele C. The Cch allele produces a silver-grey condition, called chinchilla, when present in the homozygous condition. When Cch is present with a recessive allele, a light silver-grey colour is produced. The allele Ch is recessive to both the full-colour allele and the chinchilla allele. The Ch allele produces a white colour with black extremities. This colour is called Himalayan. An allele Ca is recessive to all alleles. The Ca allele results in a lack of pigment, called albino.

9. Homework p. 149 q. 5

10. Homework p. 149 q. 5a Indicate the genotypes and phenotypes of the F1 generation from the mating of a heterozygous Himalayan rabbit with an albino rabbit. Ch Ca Phenotypic Ratios Himalayan(2):Albino(2) 50% Himalayan 50% White Ca CaCa ChCa Ca ChCa CaCa

11. Homework p. 149 q. 5b The mating of a full-colour rabbit with a light-grey rabbit produces two full-coloured offspring, one light-grey offspring and one albino offspring. Indicate the genotypes of the parents. C Ca Phenotypic Ratios FC (2) : LG (1) : Albino(1) 50% Full Colour 25% Light Grey 25% Albino Cch CchCa CCch Ca CCa CaCa

12. Homework p. 149 q. 5c A chinchilla rabbit is mated with a light-grey rabbit. The breeder knows that the light-grey rabbit had an albino mother. Indicate the genotypes and phenotypes of the F1 generation from this mating. Cch Ca Phenotypic Ratios Chinchilla (2) : Light Grey (2) 50% Chinchilla 50% Light Grey Cch CchCch CchCa Cch CchCch CchCa

13. The Sum of the Parts Independent Assortment

14. The Law of Independent Assortment • If genes are located on separate chromosomes they are inherited independently from one another. • Mendel`s studies included investigations into the inheritance of two separate characteristics during crossbreeding. He cross-pollinated plants with yellow, round seeds with plants with green, wrinkled seeds.

15. Mendel`s Cross The genotype for green colour is yy. The genotype for wrinkled seeds is rr. This pea`s genotype is yyrr. The genotype for yellow colour is YY. The genotype for round seeds is RR. This pea`s genotype is YYRR. The gametes of the yellow pea will have YR genotypes; the gametes of the green pea will have yr genotypes. The genotype of the entire F1 generation is YyRr. What will the F1 generation look like?

16. Crossing Heterozygous Round Yellow Peas YR Yr yR yr YR YYRR YYRr YyRR YyRr Yr YYRr YYrr YyRr Yyrr yR YyRR YyRr yyRR yyRr yr YyRr Yyrr yyRr yyrr

17. Phenotypic Ratios Round Yellow (9) : Wrinkled Yellow (3) : Round Green (3) : Wrinkled Green (1) The probability of producing a round, yellow pea is 9 out of 16. What are the probabilities of producing peas that have wrinkled yellow peas, round green peas and wrinkled green peas? Wrinkled Yellow 3 out of 16 Round Green 3 out of 16 Wrinkled Green 1 out of 16

18. One Trait; Multiple Genes The colour of human eyes is determined by two genes [gey2 located on c15 and gey located on c19]. These genes are located on separate chromosomes and thus sort independently. The gey gene is epistatic over the gey2 gene. This means that the gey gene influences the expression of alleles by the gey2 gene.

19. One Trait; Multiple Genes If the gey2 genotype is BB or Bb the offspring will have brown eyes regardless of the gey genotype. If the gey2 genotype is bb the offspring will have green eyes if the gey genotype is GG or Gg. If the gey2 genotype is bb the offspring will have blue eyes if the gey genotype is gg.

20. One Trait; Multiple Genes Identify the phenotypic ratios for a cross between two parents who are heterozygous for the gey2 and gey gene. The genotype for both parents is BbGg! 5:00 4:45 4:30 4:15 4:00 3:45 3:30 3:15 3:00 2:45 2:30 2:15 2:00 1:45 1:30 1:15 1:00 0:45 0:30 0:15 0:05 0:04 0:03 0:02 0:01 0:00

21. Crossing Heterozygous Brown Eyed Parents BG Bg bG bg BG BBGG BBGg BbGG BbGg Bg BBGg BBgg BbGg Bbgg bG BbGG BbGg bbGG bbGg bg BbGg Bbgg bbGg bbgg

22. Phenotypic Ratios Brown (12) : Green (3) : Blue (1) 12 in 16 chance of Brown Eyes 3 in 16 chance of Green Eyes 1 in 16 chance of Blue Eyes