Question

a.) Before individual II-2 had an affected son, this family believed the condition followed a dominant mode of inheritance.  Why does the phenotype of III-1 support a recessive rather than a dominant mode of inheritance?

Use the pedigree below for the following questions. The characteristic depicted is rare. I 2 II 1 2 3 1 Before individual II-2 had an affected son, this family believed the condition followed a dominant mode of inheritance. Why does the phenotype of III-1 support a recessive rather than a dominant mode of inheritance? TT T 4 3 (12pt) JES Arial k Save and Submit to save and submit. Click Save All Answers to save all answers. Save All A

b.) Could the mode of inheritance actually be dominant? Explain using appropriate genetic terms.

c.) In order to better understand the risk of passing this condition on to additional offspring, individual II-2 sought genetic counseling which resulted in the drawing of this pedigree. This action makes her the ______________________.

d.)

1. IF the characteristic is X-linked recessive, what are the genotypes for the following individuals?

2.What is the term for the genotype of individual III-1?

I-2:________

II-2:________

II-3:________

III-1:________

Answer 1

a) The pedigree shows X-linked (trait passes from affected or carrier female to male) recessive inheritance. The phenotype of the III-1 support recessive trait because the affected III-1 (X•Y) has both unaffected parent (XX• and XY). If it is dominant, one of those parent should be affected. Here, II-2 female parent act as carrier (XX•).

b) Only one character support that the trait is dominant that is the trait doesn't skip generations but the unaffected parent of affected III-1 support that the trait is recessive.

c) This action makes II-2 carrier of this trait.

d)

1. If it is X-linked, the genotypes of

I-2 = X•X•

II-2 = XX•

II-3 = XY

III-1 = X•Y

2. The term for the genotype of III-1 is affected male.

X'x' I 2 XY XX XY bi 2 3 XY

X'x' I 2 XY XX XY bi 2 3 XY