Exam 20: Evolution of Genes and Traits

An excess of nonsynonymous fixed mutations between species is likely due to:

Which researcher proposed that change was caused by the environment acting directly on an organism,and that those changes acquired in an organism's lifetime were passed on to its offspring?

Suppose that you have cloned and sequenced a gene that controls fruit size in strawberry.However,you do not know the function of the gene. a)Describe how you could determine if this gene is also present in Arabidopsis (which has been fully sequenced). b)Describe how you could determine if the gene is present in day lily (which has not been fully sequenced). c)How could you determine a putative function for this gene?

Define the molecular clock.

Can behaviors be the product of selection,even when their heritability is either very low or zero? Justify your answer.

What is meant by the phrase,"The force of selection is myopic."?

Some of the most striking and best understood examples of morphological divergence are found in:

Mutations within the Oca2 gene are associated with albinism and blindness in cavefish,while mutations in MC1R have been associated with increased pigmentation in the hairs of some pocket mice.With regard to protein function,compare the mutations generating each alteration of phenotype.

Inherited blindness in some cavefish arose through:

The molecular basis of sickle cell hemoglobin is:

Which of the following processes will increase variation between populations?

Following a gene duplication event,the additional copy of the gene is identical to the original copy. a)Does the duplication event,by itself,create a novel function? b)How does a gene duplication event promote the creation of a gene with a novel function?

Suppose that a population composed of 100 individuals existed on an island in the Caribbean Sea.Two different alleles of the A gene were present in this population (a¹ and a²)at equal frequency.The following events occurred to this unlucky population.Determine what evolutionary force (mutation,migration,drift,or selection)is represented by each event.In addition,tell the effect of each event on the genetic composition of the population. a)A devastating fire caused the death of 10 individuals. b)A disease swept through the island and killed 13 individuals.The a¹ confers resistance to the disease. c)A disease swept through the island killing 13 individuals.Neither a¹ nor a² confers resistance to the disease. d)A ship containing individuals from a different island containing a¹,a²,and a³ alleles landed at the island. e)The president (whose genotype is a¹a¹)declared that all a¹ individuals had more rights than a² individuals.All a² individuals moved to another island. f)An individual who was working in a cave stumbled upon a new rock and decided to put it in his pants pockets to show his wife.Some of their babies had an a⁴.

Which of the following are requirements for evolution by natural selection? I environmental change II differential survival and reproduction III heritability of phenotypic variation IV variation in phenotype V sexual reproduction

When considering the rate of nucleotide divergence for a particular gene over time,which of the following has been observed to be true?

Most genetic variation for many human loci lies within local populations rather than between populations or races.What does this observation tell you about human genetic evolution?

The rate of change is not identical for all genes.The following graph shows the rate of change of four hypothetical human proteins (A-D).Use this graph to answer the following questions. a)Which of the proteins is changing at the fastest rate? b)Which protein is most conserved? c)Which evolutionary force (drift,selection,or migration)plays the biggest role in causing the observed difference in the rate of change between proteins A-D? d)If you do Southern hybridization to determine if the genes encoding each of these human proteins (A-D)also exist in rice,which would give the strongest hybridization signal? Justify your answer. e)If you were going to use one of the proteins to build a phylogenetic tree of various mammalian species (which diverged during the last 50 million years),which protein sequence would be most useful? Justify your answer. f)If you were going to use one of the proteins to build a phylogenetic tree of various plant species (which diverged during the past 500 million years),which protein sequence would be most useful? Justify your answer. g)If you were going to use one of the proteins to build a phylogenetic tree of a mixture of plant and animal species (which diverged 1200 million years ago),which protein sequence would be most useful? Justify your answer.

Darwin's theory of evolution was developed around three central principles: the principle of variation,the principle of heredity,and the principle of selection.Define each of these principles,and explain their role in evolution.

An orchid breeder is interested in increasing the number of stems and the length of stems that can be produced by an orchid plant.She finds a segregating population that contains a wide range of both stem number (ranging from 2 to15 stems per plant)and stem length (ranging from 2 to 7 inches in length).She selected plants from this population that either had the most stems per plant or the longest stems per plant (shown as filled regions in the diagrams below).She then interbred the plants with the most stems (or the longest stems)and grew the resulting populations of orchids.Following an additional round of selection and breeding,the breeder drew graphs to look at the distribution of plants in each generation.Shown below are graphs representing the distribution of plants in each generation in terms of stem number and stem length (in inches).For each trait,determine whether or not the trait is heritable.Justify your answers.

Assume that the following amino acid sequences were obtained for a highly conserved gene,gene X,in eukaryotes.Using this information,determine the most probable ancestral amino acid sequence.