Question

A young couple is planning to have children. Knowing that there have been a substantial number of stillbirths, miscarriages, and fertility problems on the husband’s side of the family, they see a genetic counselor. A chromosome analysis reveals that, whereas the woman has a normal karyotype, the man possesses only 45 chromosomes and is a carrier of a Robertsonian translocation between chromosomes 22 and 13.

a. List all the different types of gametes that might be produced by the man.

b. What types of zygotes will develop when each of the gametes produced by the man fuse with a normal gamete produced by the woman?

c. If trisomies and monosomies of chromosomes 13 and 22 are lethal, what proportion of the surviving offspring will be carriers of the translocation?

Answer 1

If the translocation segregates away from the normal chromosome 22 and 13, then the resulting gametes will have either: compositefunction Normal chromosome 13 and normal chromosome 22 OR compositefunction Translocated chromosome 13 + 22 Rightarrow Tf the translocation and chromosome 22 segregates away from the chromosome 13, then the resulting gametes will have either compositefunction Translocated chromosome 13 + 22 and normal chromosome 22 or compositefunction Normal chromosome 13 Rightarrow If the translocation and chromosome 13 segregate away from the chromosome 22 (rare), then gametes: compositefunction Normal chromosome 13 and translocated chromosome 13 + 22 or compositefunction Normal chromosome 22 b) compositefunction 13, 13, 22, 22 compositefunction Normal compositefunction 13, 12 + 22, 22 compositefunction Translocation Carrier compositefunction 13, 13 + 22, 22, 22 compositefunction Trisomy 22 compositefunction 13, 13, 22 compositefunction Monosomy 22 compositefunction 13, 13, 13 + 22, 22 compositefunction Tresomy 13 compositefunction 13, 22, 22 compositefunction Monosomy 13 c) If all trisomies