In humans, brown eye color (B) is dominant and all others are recessive (b), and
ID: 258543 • Letter: I
Question
In humans, brown eye color (B) is dominant and all others are recessive (b), and non-red hair is dominant (W) while red hair is recessive (w). What are the phenotypes of a cross between a man heterozygous with brown eyes and homozygous dominant with non-red hair mated to a woman with blue eyes and red hair? 4. In guinea pigs, black fur is dominant (B) while white is recessive (b). Rough fur is dominant (R) while smooth is recessive () What is the probability that parents who are BBRr and BbRr wll have offispring with black smooth fur?Explanation / Answer
4. Given,
The man is heterozygous with brown eyes and homozygous dominant with non-red hair. The genotype of the man will therefore be BbWW.
The woman has blue eyes and red hair. The genotype of the woman will therefore be bbww.
Gametes formed by man will be – BW, bW
Gametes formed by woman will be bw, bw.
Punnett square for the cross is as follows:
BW
bW
bw
BbWw
bbWw
bw
BbWw
bbWw
Phenotype of the offspring will be
BbWw – Brown eye color and non-red hair
bbWw – blue eye color and non-red hair.
5. Given,
Genotype of parents is BBRr, and BbRr.
Gametes formed by BBRr parent will be – BR, Br, BR, Br.
Gametes formed by BbRr parent will be – BR, Br, bR, br.
Punnett square for the cross is as follows:
BR
BR
Br
Br
BR
BBRR
BBRR
BBRr
BBRr
Br
BBRr
BBRr
BBrr
BBrr
bR
BbRR
BbRR
BbRr
BbRr
br
BbRr
BbRr
Bbrr
Bbrr
BBRR, BBRr, BbRR, BbRr – Black rough fur – 12/16 = 0.75
BBrr, Bbrr – Black smooth fur – 4/16 = 0.25
Therefore, the probability that parents who are BBRr and BbRr will have offspring with black smooth fur is 4/16 = 0.25.
BW
bW
bw
BbWw
bbWw
bw
BbWw
bbWw