Question

dominant pedigree

1. which members of the family above are afflicted with huntingtons disease? ____________
2. there are no carriers for huntingtons disease. with this in mind, is huntingtons disease caused by a dominant or recessive trait? ____________
3. how many children did individuals i-1 and i-2 have? ____________
4. how many girls did ii-1 and ii-2 have? __________ how many have huntingtons disease? __________
5. how is individual iii-2 and ii-4 related? __________ i-2 and iii-5? __________

Explanation:

1. Shaded symbols in the pedigree represent individuals afflicted with the disease.
2. Dominant genetic disorders have no carriers—individuals either have the disease (dominant allele) or do not (recessive alleles only).
3. Count all individuals in generation II who are children of I-1 and I-2.
4. Count female (circle) children of II-1 and II-2, then count how many of those are shaded.
5. II-4 is the uncle of III-2 (brother of III-2's mother II-2); I-2 is the great-grandmother of III-5 (grandmother of III-5's father II-4).

Answer:

1. I-1, II-2, II-3, II-7, III-3
2. Dominant
3. 5
4. 2; 1
5. They are niece and uncle (or aunt and nephew, with III-2 as niece, II-4 as uncle); They are great-grandmother and great-grandson (I-2 is great-grandmother, III-5 is great-grandson)