Chapter 14: Evolutionary Mechanisms

Question 1

Describe random assortment:

Answer 1

A random assortment of chromosomes during meiosis results in gametes that have a huge number of possible combinations of the chromosomes that originally came from the male parent and the female parent.

Question 2

Describe crossing over:

Answer 2

Crossing over of chromatids during meiosis may result in pieces of chromatid being broken off and attaching to a different chromatid. This results in a changed sequence, or recombination, of the alleles along the resulting chromosome.

Question 3

What is non-disjunction ?

Answer 3

Where one or more members of a chromosome pair fail to seperate during meiosis. This results in gametes that have more or less than the correct number of chromosomes. If such gametes are involved in fertilisation, the resulting embryo will have the incorrect number of chromosomes.

Question 4

What is random fertilisation ?

Answer 4

Because one person will produce a large number of different sperm or eggs with respect to the alleles each contains, and because any sperm can fertilise any egg, there is an almost infinite number of possible combinations of alleles in the offspring.

Question 5

Describe the process of natural selection:

Answer 5

If natural selection is operating on some characteristics at the expense of others then over time, the allele frequencies for that characteristics will change. When such a situation occurs, nature is favouring one set of alleles at the expense of others, this is referred to as natural selection.