Question

Base your answer on the pedigree chart below and on your knowledge of biology. The pedigree chart represents the inheritance of color blindness through three generations. Mary and Steve are expecting another child. What is the probability that the new baby will be colorblind

Answer 1

1/2 or 50%

Step-by-step explanation:

The probability would be 1/2 or 50%.

Color blindness is generally an X-linked recessive traits. Since males only have one X chromosome, they are either affected or not affected but females with two X chromosomes can be a carrier in addition to being affected or unaffected.

Also, males usually get their X chromosomes from their mothers while the two X chromosomes in females are contributed by each parents.

Let the allele for colour blindness be b.

Genotype of Steve would be
`X^bY`

Since, they produced a male child with color blindness, Mary is a carrier with the genotype:
`X^BX^b`

`X^bY` x
`X^BX^b`

progeny: X^BX^b (carrier female), X^bX^b (affected female), X^BY (unaffected male), and X^bY (affected male)

Probability of producing color blind children = 2/4 = 1/2

Hence, the probability of their new born baby being color blind remains 1/2 or 50%