Question

1. Why are abnormalities in the number of sex chromosomes in mammals usually less severe in their phenotypic effects than abnormalities in the number of autosomes?

2. Certain trees are known to occur with several different chromosome numbers. Individuals with the somatic chromosome numbers of 28, 56, 70, and 84 have been identified. With regard to chromosome number, what would be the designation given to these different individuals?

3. The following pair of chromosomes is present in an inversion heterozygote. Å marks the placement of the centromere.

Å A B C D E F G and Å a b f e d c g If a crossover event takes place between D and E in meiosis, what will the resulting products look like?

Answer 1

Answer1]

abnormalities in the number of sex chromosomes in mammals usually less severe in their phenotypic effects than abnormalities in the number of autosomes because The effects of extra Y chromosomes are relatively mild because the mammalian Y chromosome is largely heterochromatic and contains very few genes.

extra X chromosomes have milder effect campared to autosomes because,in mammals ,all X chromosome except one are genetically inactivated very early in the embryonic development.