Question

1. black coat is dominant over white coat in guinea pigs. a homozygous black pig is mated with another homozygous black pig.

(a) what are the genotypes of the parents?
(b) what will be the genotypes, phenotypes, and probabilities of the first generation?
(c) what is the probability that white offspring will be produced?

1. a heterozygous black pig is mated with a homozygous black pig.

(a) what are the genotypes of the parents?
(b) work the problem showing the possible genotypes and phenotypes of the offspring and the probabilities of each.

1. a black pig is mated to a white pig. in the f₁ generation there are 5 black and 5 white pigs. give the genotypes of the parents.

Explanation:

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Problem 1

Step1: Define allele notation

Let $B$ = dominant black allele, $b$ = recessive white allele.

Step2: Identify parent genotypes

Homozygous black = $BB$. Both parents are $BB$.

Step3: Set up Punnett Square

	$B$	$B$
$B$	$BB$	$BB$

Step4: Calculate F1 probabilities

All offspring are $BB$, so 100% black. White offspring probability = 0.

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Problem 2

Step1: Identify parent genotypes

Heterozygous black = $Bb$, homozygous black = $BB$.

Step2: Set up Punnett Square

	$B$	$B$
$b$	$Bb$	$Bb$

Step3: Calculate offspring probabilities

$\frac{2}{4}=50\%$ $BB$, $\frac{2}{4}=50\%$ $Bb$; all black phenotype.

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Problem 3

Step1: Analyze F1 ratio

5 black : 5 white = 1:1 ratio, a test cross result. White pig is $bb$, so black parent must be $Bb$ to pass $b$ allele.

Answer:

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Problem 1

(a) Both parents: $BB$
(b)

Genotypes	Phenotypes

(c) $0$

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Problem 2

(a) Heterozygous black: $Bb$; Homozygous black: $BB$
(b)

Genotypes	Phenotypes

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Problem 3

Black parent: $Bb$; White parent: $bb$