is dominant over albino, and short hair is dominant over long hair. The phenotyp

Question

is dominant over albino, and short hair is dominant over long hair. The phenotypic results of five crosses are shown below. (D dark coat: A-albino coat: s short hair, L-long hair) (3 pts total) 2 In guinea pigs,genes ontrolling coat color and hair length assort independently, Dark coat color Number of progeny Cross Parental phenotypes D,S D,L A,S A, L D.SxD, S 2 ASx A, S D.Lx D, L 88 31 29 12 0 0 29 3 31 31 | 30 | io | 10 Provide the genotype of the underlined parent only in each cross. Use the symbols A and a for the dark and albino coat alleles and the symbols H and h for the short- and long-hair alleles, respectively. (0.5 pt each, 2 pts total) a. Cross Parent genotype b. The starred, non-underlined parents from Crosses 2 and 4 (A, S and D, S respectively) are crossed together. What progeny phenotypes do you expect, and in what proportions? (1 pt)

Explanation / Answer

Given allele for dark coat is A,

allele for albino coat is a,

allele for short hair is H,

allele for long hair is h

Now, analyzing the phenotypic table:

All the ratios are in order  Dark coat short hair :  Dark coat long hair: Albino coat short hair : Albino coat long hair

Cross 1: Parental phenotype for both is Dark coat, Short hair, Ratio = 9;3;3;1

So, Possible genotypes are AAHH, AaHh, AaHH, AAHh

None of the parental type can be AAHH, AaHH, AAHh because then there will be no Albino aoat long hair

So, parental genotype for Cross 1 is AaHh

Cross 2: Parental phenotype for both is Albino coat short hair, Ratio = 0:0: 3:1 i.e. Dark coat short hair and dark coat long hair were not there

Now possible genotypes aaHH, aaHh

If both would be aaHH, then there cannot be aahh i.e. albino coat long hair

If one is aaHh and aaHH, then progeny would be albino coat long hair (aahh) and albino coat short hair (aaHH) in ratio of 1:1,

As the actual ratio is 3:1, both the parents have genotype aaHh.

Cross 3: Parental phenotype for both is Dark coat long hair, Ratio = 0:3: 0:1 i.e. Dark coat short hair and albino coat short hair are not there

Possible parental genotypes : AAhh or Aahh

As per observed phenotypic ratio of progeny, both parents have genotype = Aahh

Cross 4: Parental phenotypes are Dark coat short hair (possible genotypes : AAHH, AaHh, AaHH, AAHh) and Dark coat long hair (possible genotypes: AAhh, Aahh), phenotypic ratio = 3:3:1:1

Phenotypic ratio indicates that the genotype of parent with dark coat short hair is AaHh

genotype of parent with dark coat long hair is Aahh

Answer a) Genotype of underlined parent:

Cross 1 D, S i.e. dark coat short hair is AaHh

Cross 2 A, S i.e. albino coat short hair is aaHh

Cross 3 D, L i.e. dark coat long hair is Aahh

Cross 4 D, L i.e. dark coat long hair is Aahh

Answer b) Genotype of Starred parents

Cross 2 : A, S* i.e. albino coat short hair is aaHh

Cross 4 : D, S* i.e. dark coat short hair is AaHh

Crossing between aaHh x AaHh

AaHH

Dark coat, short hair

AaHh,

Dark coat, short hair

aaHH,

Albino coat, short hair

aaHh,

Albino coat, short hair

AaHh

Dark coat, short hair

Aahh

Dark coat, long hair

aaHh

Albino coat, short hair

aahh

Albino coat long hair

Phenotypic ratio: Dark coat short hair :  Dark coat long hair: Albino coat short hair : Albino coat long hair is 3:1:3:1

Gametes AH Ah aH ah aH

AaHH

Dark coat, short hair

AaHh,

Dark coat, short hair

aaHH,

Albino coat, short hair

aaHh,

Albino coat, short hair

ah

AaHh

Dark coat, short hair

Aahh

Dark coat, long hair

aaHh

Albino coat, short hair

aahh

Albino coat long hair

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