Deck 25: Evolutionary Genetics

Question 1

Biological evolution is genetic change that takes place within a group of organisms. Anagenesis is evolution that takes place within a single lineage; cladogenesis is the splitting of one lineage into two.
-Briefly describe how evolution takes place as a two-step process.

Answer 1

First genetic variation arises. Then various evolutionary forces cause changes in the frequency of genetic variants.

Question 2

The application of electrophoresis to the study of protein variation in natural populations revealed that most organisms possess large amounts of genetic variation. The neutral-mutation hypothesis proposes that most molecular variation is neutral with regard to natural selection and is shaped largely by mutation and genetic drift. The balance hypothesis proposes that genetic variation is maintained by balancing selection.

-Which statement is true of the neutral-mutation hypothesis?

A) All proteins are functionless.
B) Natural selection plays no role in evolution.
C) Most molecular variants are functionally equivalent.
D) All of the above.

Answer 2

Most molecular variants are functionally equivalent.

Question 3

Variation in DNA nucleotide sequence can be analyzed by using restriction fragment length polymorphisms, microsatellites, and data from direct DNA sequencing.
-What are some of the advantages of using microsatellites for evolutionary studies?

Answer 3

Microsatellites are often highly variable among individuals. They can be amplified with the use of PCR, and so they can be detected with a small amount of starting DNA. Finally, the detection and analysis of microsatellites can be automated.

Question 4

The biological species concept defines a species as a group of potentially interbreeding organisms that are reproductively isolated from the members of other species. Under this concept, species are separated by reproductive isolating mechanisms, which may intervene before a zygote is formed (prezygotic reproductive isolating mechanisms) or after a zygote is formed (postzygotic reproductive isolating mechanisms).

-Which statement is an example of postzygotic reproductive isolation?

A) Sperm of species A dies in the oviduct of species B before fertilization can take place.
B) Hybrid zygotes between species A and B are spontaneously aborted early in development.
C) The mating seasons of species A and B do not overlap.
D) Males of species A are not attracted to the pheromones produced by the females of species B.

Question 5

Allopatric speciation is initiated by a geographic barrier to gene flow. A single population is split into two or more populations by a geographic barrier. With the passage of time, the populations evolve genetic differences, which bring about reproductive isolation. After postzygotic reproductive isolating mechanisms have evolved, selection favors the evolution of prezygotic reproductive isolating mechanisms.
-What role does genetic drift play in allopatric speciation?

Question 6

A phylogeny represents the evolutionary relationships among a group of organisms and is often depicted graphically by a phylogenetic tree, which consists of nodes representing the organisms and branches representing their evolutionary connections.

-Which feature is found in a rooted tree but not in an unrooted tree?

A) Terminal nodes
B) Internal nodes
C) A common ancestor to all other nodes
D) Branch lengths that represent the amount of evolutionary divergence between nodes

Question 7

Different genes and different parts of the same gene evolve at different rates. Those parts of genes that have the least effect on function tend to evolve at the highest rates. The idea of the molecular clock is that individual proteins and genes evolve at a constant rate and that the differences in the sequences of presentday organisms can be used to date past evolutionary events.

-In general, which types of sequences are expected to exhibit the slowest evolutionary change?

A) Synonymous changes in amino acid coding regions of exons
B) Nonsynonymous changes in amino acid coding regions of exons
C) Introns
D) Pseudogenes