Download In-class Exercise Biology 101 Discussion: During lecture on 5/22/08

Discussion: During lecture on 2/7/17
1. We have learned that crossing over increases the genetic diversity in a population because it
reshuffles the genes of homologues. Some species have lost the ability to cross over and in other
species, like humans, have lost the ability in certain chromosomes. What factors do you think could
reduce levels of recombination between homologues?
2. Many species can reproduce either asexually or sexually. It is often when the environment changes
in some way that is unfavorable to a population that the organisms begin to reproduce sexually.
Speculate about the evolutionary significance of this switch from asexual to sexual reproduction.
3. Among the great apes, humans have 23 pairs of chromosomes, and the great apes have 24 pairs.
Given that we share an ancestor with the great apes, scientists have hypothesized that the
reduction in chromosomal number for humans occurred either by the deletion of a homologous pair
or by two chromosomes fusing together. Which hypothesis do you think is more likely and how
might you test your hypothesis?
In-class Exercise Biology 101
Discussion: During lecture on 5/22/08
1. Labrador retrievers can have coat colors of black, chocolate, and yellow. Black coat color has been
shown to be dominant over chocolate coat color but how might your group explain yellow coat
color?
2. Many animals show a phenomena known as “point restriction” where they have light fur color over
the majority of their body even though their genotype should have dark fur color all over the body.
Only in ‘restricted’ regions of the body such as the exterminates (ears, feet, nose) does the dark fur
appear. Can your group hypothesis a mode of inheritance for these “point restrictions”?
3. One of the genes for baldness is located on the X chromosome and is recessive to the allele for
normal hair at the same gene. If a bald male were to marry a carrier female, what would be the
probability that the first-born son would be bald? What percentage of the females produced in this
liaison would be carriers?