please help 2. A rane A husband and wife phenotypically normal had a son with si

Question

please help

2. A rane A husband and wife phenotypically normal had a son with sickle cell anemia a) What are the genoxypes of the husband and wife? b) What is the probability that the couple's second child wouald have sickle cell anemia? Car c) If you know that none of the child's grandparents had sickle cell anemia, can you accuradely pre- dict the genotype for all four of the grandparents? Dihybrid Problems 1. In dogs, dark coat color is dominant to albinism, and shon-haired coat is dominant to long-haired cot. a) If a dog pure-breeding for dark, short cout is crossed with an alhino, long haired dog, what geno- types and phenotypic ratios do you expect in the offspring? b) If the pups are raised and then allowed to mate amongst themselves, what genotypes and pheno- typic ratios do you expect in the offspring? 2. In watermelons, the allele for green rinds is dominant to the allele for striped rind, and the allele for short fruits is dominant to the allele for long fruits. The genes for color and length are on different pairs of chromosomes Assume that you have two true-breeding varieties, one of which produces green and shont melons and the other of which produces striped and long melons. Describe the steps you would take to get plants that produce true-breeding green, long melons. Suggestion: Work through the Punnett square for the dihybrid cross to determine the number of dif ferent genotypes resulting from the mating that will yield green, long melons. Then use the test-cross.)

Explanation / Answer

Sickle cell anemia is an autosomal recessive trait.

Parental cross: Ss X Ss

Progeny: SS Ss Ss ss

The probability for homozygous recessive is 1/4 irrespective of the number of birth as each birth is an independent and random event.

Maternal grandparents: SS X Ss (Or Ss X Ss)

Paternal grandparents: SS X Ss (Or Ss X Ss)

Dihybrid problem 1.

a. Dark coat color = D

Albinism = d

Short hair = S

Long hair = s

Parental cross: DDSS X ddss

Progeny: DdSs

Genotypic ratio = All dogs with double heterozygous genotype

Phenotypic ratio = All dogs show dark and short-haired coat.

b. F1 selfing: DdSs X DdSs

Progeny:

Genotypic ratio = 1:1:1:1:2:2:2:2:4

Phenotypic ratio:

S_D_ = 9 = Short and dark

ssD_ = 3 = Long and dark

S_dd = 3 = Short and albino

ssdd = 1 = Long and albino

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