PLEASE ANSWER ALL QUESTIONSIF YOU CANNOT DO NOT ANSWER 6 Col

PLEASE ANSWER ALL QUESTIONS...IF YOU CANNOT DO NOT ANSWER

6. Colorblindness is a phenotype caused by an X-linked, recessive allele (X^b). Jonathan is colorblind, but his mother is not. Which of the following is a possible genotype of his mother? (Here, X^B refers to the dominant, X-linked allele that does not cause colorblindness.)

X^b X^b

X^B X^b

X^B X^B

X^b Y

7. If Jonathan\'s mother has another son with Jonathan\'s father, who is not colorblind, what is the probability that her new son will also be colorblind? (Hint: Complete a Punnett square for Jonathan\'s mother and father.)

0%

25%

50%

100%

8. In Nina Jablonski\'s article, she explains that dark skin pigmentation in humans was historically a beneficial phenotype in __________ environments. (More than one answer may be correct!)

high UVA

low UVA

low latitude (tropical)

high latitude (polar)

Solution

Answer:

6). B. XB Xb

The X chromosomes of son will get from the mother. If the mother is heterozygous for the colorblindness, the trait can not be expressed in the mother as it is X-linked recessive disorder. But, 50% of her sons will get the disease.

7). C. 50%

XB Xb (mother, normal) x   XB Y(father, normal)

XB

Y

XB

XB XB (normal female)

XB Y (normal male)

Xb

XB Xb (normal female)

Xb Y (colorblind male)

50% sons are colorblind and the remaining 50% sons are normal.