In guinea pigs, the allele for black fur (B) is dominant over the allele for white fur (b)… — Armed Services Vocational Aptitude Battery (ASVAB)

In guinea pigs, the allele for black fur ( $B$ ) is dominant over the allele for white fur ( $b$ ). If two heterozygous ( $Bb$ ) guinea pigs mate, what percentage of their offspring is expected to have white fur?

A
$75\%$
B
$50\%$
$25\%$ Cevap
D
$0\%$

Cevap

25\%

of the offspring are expected to have white fur.

In a cross between two heterozygous parents (

Bb \times Bb

), each parent contributes a recessive allele (

b

) with a probability of

\frac{1}{2}

. The probability of producing a homozygous recessive offspring (

bb

) is

\frac{1}{2} \times \frac{1}{2} = \frac{1}{4}

, or

25\%

. Since white fur is recessive, only the

bb

genotype displays white fur.

Adım Adım Çözüm

Determine the parental genotypes and possible gametes.

Both parents have the heterozygous genotype

Bb

, producing gametes carrying either allele

B

or allele

b

with equal probability.

Heterozygous organisms possess one dominant allele and one recessive allele for a given gene.

Construct a Punnett square to determine all possible offspring genotypes.

The resulting genotypic ratio is

1\ BB

(

25\%

2\ Bb

(

50\%

), and

1\ bb

(

25\%

Mendel's Law of Segregation states that allele pairs separate during gamete formation and recombine randomly at fertilization.

Determine the phenotype associated with white fur.

Only the homozygous recessive genotype (

bb

) results in white fur, representing

1

out of

4

combinations (

25\%

Because the black fur allele (

B

) is dominant, any individual with at least one

B

allele (

BB

Bb

) will display black fur.

Anahtar Kavram

Monohybrid cross phenotypic and genotypic ratios in Mendelian inheritance

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Soru

Cevap

Adım Adım Çözüm

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