Biology 1202: MasteringBiology Chapter 23
Crossing over, resulting in an increase in genetic variation, occurs between _____.
Nonsister chromatids of homologous chromosomes. [This process produces chromosomes containing genes inherited from both parents.]
(Click on the diagram to start the animation.) This animation illustrates _____ as it occurs during _____.
crossing over ... prophase I. [Crossing over, the exchange of genetic material between the nonsister chromatids of homologous chromosomes, occurs during prophase I.]
Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population?
Alleles that promote "tallness" will decrease in frequency. [A reduction in "tallness" alleles is the change expected as a result of this type of selection.]
(Click on the diagram to start the animation.) Which of these gametes contain one or more recombinant chromosomes?
B, C, F, and G. [These gametes carry chromosomes produced as a result of crossing over.]
The ease with which humans travel across the globe is likely to increase _____.
Gene flow. [When people travel or migrate, they take their alleles with them.]
A mutation occurs when _____.
There is a change in the DNA sequence of a gene [This is the definition of mutation.]
Genetic drift is a process based on _____.
The role of chance.
In human gamete production there is an average of _____ crossover events per chromosome pair.
2-3. [These crossover events increase the genetic variation among gametes.]
Which of these individuals is a homozygous genotype?
AA [When both of the alleles of a given gene pair are the same, the individual is homozygous for that gene.]
All the genes in a population are that population's _____.
Gene pool. [All the alleles of all the genes of a population make up a gene pool.]
Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.
Genetic drift. [Modern travel and migration decreases the chances of there being a small, isolated population.]
Homologous pairs of chromosomes are lined up independently of other such pairs during _____.
Metaphase I.