Evolution chapter 8

A gene tree is a

• method used to determine time based on base pairsubstitutions.

• group of organisms that a taxonomist judges to becohesive units.

• group of functionally related genes located closeenough together that they segregate as a single unit.

• branched genealogical lineage of homologous allelesthat traces their evolution back to an ancestral allele.

Coalescence is the

• removal of deleterious alleles from a population.

• movement of alleles from one species orpopulation to another.

• persistence of a genetic polymorphism throughseveral speciation events.

• process in which the genealogy of any pair of homologous alleles merges in a common ancestor.

Which two phenomena can increase the rate ofcoalescence, causing more coalescent events closer to thetips of a gene tree than expected?

• positive selection and increased population size

• bottleneck events and decreased population size

• positive selection and decreased population size

• balancing selection and increased population size

Which pair is an example of orthologs?

• HIV-1 and SIV viruses

• hemoglobin subunits in humans

• BRCA1 in humans and Brca1 in mice

• the G variant and T variant of BRCA1

A paralog is

• a homologous gene that arises by gene duplication.

• a derived form of a trait that is shared by a group of related species.

• one of two or more homologous genes separatedby a speciation event.

• a noncoding stretch of DNA containing a string of short repeated segments.

When the hybrid offspring of interbreeding speciessurvive and mate with individuals from one of theparent species, this creates a phenomenon known as

• coalescence.

• introgression

• genetic hitchhiking.

• incomplete lineage sorting.

The gene tree of a particular sequence from a species___________ correlate with the phylogeny of aspecies

• may or may not

• will invariably

Which scenario would cause incomplete lineage sorting?

• A favorable allele fixes in the population very quickly.

• A hybrid offspring mates with individuals from theoriginal species.

• A substitution occurs that alters the amino acidsequence of a protein

• All the alleles of interest are present before thedivergence of species.

Which is not a source of error when constructing genetrees?

• introgression

• synapomorphies

• molecular homoplasy

• incomplete lineage sorting

A statistical method for reconstructing phylogenies thatidentifies the tree topology that minimizes the totalamount of change required to fit the data to the tree is

• neighbor joining.

• maximum likelihood.

• maximum parsimony.

• distance-matrix method.