Question

17 multiple choice 1 point
in humans skin color is polygenic with more dominant alleles being associated with more melanin, the pigment that gives human skin its color, and therefore darker skin. some humans have a condition known as albinism. albinism is an inherited condition that leads to someone having very light skin, hair, and eyes. what is the most likely genotype of an individual with albinism, if skin color is controlled by 3 genes?
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18 multiple choice 1 point
in chickens feather color is codominant with three phenotypes present: white, black, and white with black spots. if a white chicken is crossed with a spotted chicken what is the probability of each phenotype in the next generation?
0 white : 0 black : 1 spotted
1 white : 0 black : 1 spotted
0 white : 1 black : 1 spotted
1 white : 1 black : 2 spotted

Explanation:

For Question 17

Step1: Recall albinism genetics

Albinism occurs when no dominant alleles (which produce melanin) are present for the polygenic skin color trait.

Step2: Match to genotype

For 3 skin color genes, the only genotype with no dominant alleles is all recessive.

Step1: Define codominant alleles

Let $W$ = white allele, $B$ = black allele. White chickens are $WW$, spotted chickens (codominant) are $WB$.

Step2: Set up Punnett square

Cross $WW \times WB$:

Gametes	$W$	$W$
$B$	$WB$	$WB$

Step3: Calculate probabilities

$WW$ (white): $\frac{2}{4} = 50\%$, $WB$ (spotted): $\frac{2}{4} = 50\%$, $BB$ (black): 0. Simplify to ratio.

Answer:

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For Question 18