Question

Which observation would be the best evidence for a recent founder event or population bottleneck?

Seleccione una:
a. Evidence that a specific genotype has a strong selective advantage in an environment
b. Census evidence for a steadily growing population
c. Evidence that population size on an island is maintained by a steady influx of migrants from the mainland
d. Roughly equal genetic variation in all subregions of a species range
e. Low genetic diversity in a single population of a widely distributed species

Which bit of genetic material would be under the greatest selective constraint?

Seleccione una:
a. Second position nucleotides of codons in a pseudogene
b. An exon that codes for the active site of a protein enzyme
c. A chromosomal region with a high recombination rate
d. DNA in the centromere of a chromosome
e. Nucleotides found at the first position of codons in an intron

Answer 1

1. E.
Founder effect or population bottleneck refer to events which bring about reduction in the genetic variability of a particular specie population. Such events typically drastically reduce the gene pool of the population and produce a smaller number of population with less genetic diversity. An example of a population bottleneck is a genocide event. Such event will destroy a large percentage of the affected population leaving only a smaller population with less genetic diversity.
2. B.
Selective constrain refers to the selective function of the gene, which determine the amount of beneficial or neutral mutations that can occur in a particular gene. The rate at which a gene can be substituted for another one determine the level of selective constrain that can be expressed in a gene. Low selective constrain brings about genetic variability while high selective constrain discourages it. For proteins generally, there is usually high selective constrain, this is because, substitution of a codon for another one will lead to the production of a protein that will not be functional.