BIO CH. 23

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Natural selection changes allele frequencies because some _________ survive and reproduce more successfully than others.
a. alleles
b. loci
c. gene pools
d. species
e. individuals

E

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is:
a. new mutations that occurred in the preceding generation.
b. genetic drift due to the small size of the population.
c. the reshuffling of alleles in sexual reproduction.
d. geographic variations within the population.
e. environmental effects.

C

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating:
a. the bottleneck effect.
b. disruptive selection.
c. frequency-dependent selection.
d. neutral variation.
e. stabilizing selection

E

The nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?
a. gene variability= 0%; number of alleles = 0
b. gene variability= 0%; number of alleles = 1
c. gene variability= 0%; number of alleles = 2
d. gene variability >0%; number of alleles = 2
e. Without more information, gene variability and number of alleles cannot be determined.

B

There are 40 individuals in population 1, all with genotype A1A1, and there are 25 individuals in population 2, all with genotype A2A2. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is most likely an example of :
a. genetic drift.
b. gene flow.
c. disruptive selection.
d. discrete variation.
e. directional selection.

A

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy- Weinberg equilibrium, what proportion of the flies carry both A1 and A2?
a. 0.70
b. 0.49
c. 0.21
d. 0.42
e. 0.09

D

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