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In: Biology

In rabbits, black hair depends on a dominant allele, B. and brown on a recessive allele,...

In rabbits, black hair depends on a dominant allele, B. and brown on a recessive allele, b. Short hair is due to a dominant allele, S, and long hair to a recessive allele, s. A short, black haired male rabbit who is homozygous dominant for both traits is mated with a brown, long haired female
a. Write the genotype (in letters) of both parents.
b. Draw the Punnett square below illustrating the cross of the parental rabbits.
c. What percentage of the offspring have long brown hair?
d. Two other rabbits are mated. The male has long, black hair and is heterozygous for hair color. The female has short, brown hair and is heterozygous for hair length. Draw this Punnett square below. What percentage of the offspring have short black hair?

Solutions

Expert Solution

Black hair rabbit will be BB
Brown hair rabbit will be bb

Short hair rabbit will be SS
Long hair rabbit will be ss

a) Genotype of both the parents since they are homozygous will be

Parent 1 with Black and short hair will be BBSS

Parent 2 with Brown and long hair will be bbss

b) The cross of the parental rabbits will be

BS X bs (since both the alleles in each parent is same due to the homozygous nature )

When we do a punnet cross we see the following :

bs BbSs

Which means that all of the offsprings after mating will have a genotype of BbSs where the dominants will rule resulting in the phenotype of Black and short haired rabbits.

c) The percentage of the offsprings having brown and long haired rabbit is 0%

Since all the offprings will have a dominant alllele resulting in all of them being Blalck and short haired.

d) When two other rabits were mated

Parent one : Long black hair(heterozygous) , the genotype will be Bbss

Parent two : Short(heterozygous) bown hair, the genotype will be bbSs

When we mate the two genotypes, it will be

Bbss X bbSs

the following allelelic combination can be used

which would be

Parent 1 : Bs and bs

Parent 2 : bS and bs

When we do a cross between them, we get the following results:

bS bs

Bs BbSs Bbss

bs bbSs bbss

Now we need to find out the percentage of offsprings having short and black hair

To have a short hair we need the dominant trait S

to have black hair we need a dominant trait B

Out of the 4 offsprings, BbSs is the only offspring with the character which means 1/4 offsporings will show short and black hair character.

which means 1/4* 100 = 25

therefore the answer is = 25%

I hope i was able to help you with the answers !:)

gladiator answered 1 year ago

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