Genetics 301, Spring 2003
Homework Assignment #4
Problems 4.9 (also calculate distance of genes from centromere), 4.11, 5.1, 5.6, 5.8.
Also, try the following problems:
- A DNA marker (21-33) has been mapped to the centromere region of chromosome 21. The mother of a girl with Down syndrome (trisomy 21) is heterozygous for two alleles at the 21-33 locus, a and b. The father is homozygous for the c allele at the 21-33 locus. DNA testing demonstrates that the girl has all three alleles, a, b and c at the 21-33 locus. What does this indicate about the parent that contributed the extra chromosome 21 in this girl, and which meiotic division the error occurred in ?
- A man with normal vision marries a color blind woman (X-linked recessive). The man has the a allele of the X-linked gene glucose-6-phosphate dehydrogenase,(G6PDH) while the woman is heterozygous for the b and c alleles at that gene. They have a son with Klinefelter (XXY) syndrome and normal vision who is heterozygous for the a and b alleles of G6PDH. What does this indicate about the nondisjunction which resulted in their son’s chromosome abnormality?