The quiz is worth 25 points,
5 points each for parts a through e.
a) Paul's X chromosome has a pericentric inversion
b) Nancy received an inverted X from Paul, and a normal one from Donna, so
she is heterozygous for the inversion, and her two Xs would form a loop when
pairing in meiosis. The centromeres of the Xs would be within the loop.
c) Only the daughters are inversion heterozygotes. The sons received only
one X, the normal one from Donna. All daughters received Paul's inverted X
as well as one of Donna's normal Xs.
d) When Nancy's Xs formed the loop for meiotic pairing, a crossover occurred
within the loop. Jeff's X represents one of the resulting recombinant
e) Jeff's X contains both duplications and deficiencies. The telomeric
regions of his X both represent the telomeric region of the short arm of the
normal X, so this region is duplicated in him. He has no copy of the normal
distal portion of the long arm. Duplications and deficiencies represent
unbalanced karyotypes, and phenotypic abnormalities arise from this
incorrect gene dosage.