Exam 23: Evolution of Genes and Genomes

Which animals are foregut fermenters?

Refer to the figure showing the hypothetical observed sequences from two related species and their common ancestor. If we only had information from species 1 and species 2, how many substitutions could be inferred?

Suppose the size of a population of crickets is 1,500.According to the theory that neutral variants accumulate through genetic drift, what is the probability that a newly arisen neutral mutation will become fixed in this population?

Consider the great diversity of genome size among organisms.As genome size increases, the relative proportion of noncoding DNA

Refer to the figure. Members of the JAK family of nonreceptor kinases are involved in signaling pathways.The four paralogs JAK1, JAK2, JAK3, and TYK2 are found in humans, mice, chickens, and fish, as shown in the phylogenetic tree.According to this phylogenetic gene tree,

______ were used by investigators to study the loss of genetic material in different insects.

A gene family has been accumulating nucleotide substitutions at a rate of 0.25 per million years.On average, there have been 80 substitutions between the common ancestor of this gene family and each of the various living forms of this gene.How many substitutions are expected to have evolved between any pair of living forms of genes from this gene family?

Puffer fish are resistant to poisoning by TTX, a sodium channel toxin that they produce as a defensive mechanism.TTX cannot bind to puffer fish sodium channels, because _______ nucleotide substitutions in the sodium channel gene have altered the protein structure such that the TTX binding site is lost without affecting the function of the sodium channel.

Which of the following processes or events is most likely to cause gene trees to not reflect the evolutionary history of a species?

Homologous genes from three different species are compared with the gene sequence of their most recent common ancestor.It is found that at nucleotide position 36 there are identical nucleotide substitutions for all three species.This is evidence for _______ substitutions at this position.

A parallel substitution occurs when

Two species of plants that diverged 20 million years ago have accumulated an estimated 10 nucleotide differences in gene X.Species A has had an average population size of 3 million, while species B has had an average population size of 0.5 million.Both of these plants are annuals, with one generation per year.Suppose that a sequence analysis of offspring and parents shows that the actual total mutation rate is 1.5 per million.Assuming that all mutations are either deleterious or neutral, approximately what fraction of the mutations are deleterious?

Which observation is contrary to the neutral theory of molecular evolution?

In which group would you expect the greatest extent of lateral gene transfer to take place?

The globin gene family is an example of

The bacterium Thermus aquaticus produces a reverse transcriptase that can withstand the high temperatures in PCR that are required for the two strands of the DNA template to dissociate.The search for and discovery of T.Aquaticus-derived reverse transcriptase is a prime example of _______.

A nematode has a gene that is not found in any closely related species.A similar gene, however, is found in a variety of insects.What is the most likely explanation for this observation?

Refer to the figure, which shows the process of in vitro evolution of a new RNA molecule. In which numbered step is reverse transcriptase used?

When a gene duplication occurs, _______ nucleotide substitutions are required for the evolution of a gene with a new function.

A gene that codes for a cardiac glycoside, which can be deadly if ingested, is found in two species of oleander plant.These _______ genes are _______.