Exam 9: How Genes and Genomes Evolve

For each of the following sentences, fill in the blanks with the best word or phrase in the list below.Not all words or phrases will be used; use each word or phrase only once. divergence purifying selection exon shuffling single-nucleotide polymorphisms gene duplication synteny horizontal gene transfer unequal crossing-over __________ may arise by recombination within introns and can create proteins with novel combinations of domains.Scientists and government regulators must be very careful when introducing herbicide-resistant transgenic corn plants into the environment, because if resistant weeds arise from __________, then the herbicides could become useless.Families of related genes can arise from a single ancestral copy by __________ and subsequent __________.

Which of the following statements about mobile genetic elements is TRUE?

Which of the following regions of the genome is the LEAST likely to be conserved over evolutionary time?

You are working in a human genetics laboratory that studies causes and treatments for eye cataracts in newborns.This disease is thought to be caused by a deficiency in the enzyme galactokinase, but the human gene that encodes this enzyme has not yet been identified.At a talk by a visiting scientist, you learn about a strain of baker's yeast that contains a mutation called gal1^- in its galactokinase gene.Because this gene is needed to metabolize galactose, the mutant strain cannot grow in galactose medium.Knowing that all living things evolved from a common ancestor and that distantly related organisms often have homologous genes that perform similar functions, you wonder whether the human galactokinase gene can function in yeast.Because you have an optimistic temperament, you decide to pursue this line of experimentation.You isolate mRNA gene transcripts from human cells, use reverse transcriptase to make complementary DNA (cDNA) copies of the mRNA molecules, and ligate the cDNAs into circular plasmid DNA molecules that can be stably propagated in yeast cells.You then transform the pool of plasmids into gal1^- yeast cells so that each cell receives a single plasmid.What will happen when you spread the plasmid-containing cells on Petri dishes that contain galactose as a carbon source? How can this approach help you find the human gene encoding galactokinase?

The evolutionary relationships between seven different species-G, H, J, K, L, M, and N-are diagrammed in Figure 9-25. Figure 9-25 Given this information, which of the following statements is FALSE?

Some types of gene are more highly conserved than others.For each of the following pairs of gene functions, choose the one that is more likely to be highly conserved. A.genes involved in sexual reproduction; genes involved in sugar metabolism B.DNA replication; developmental pathways C.hormone production; lipid synthesis

In humans and in chimpanzees, 99% of the Alu retrotransposons are in corresponding positions.Which of the following statements below is the most likely explanation for this similarity?

Which of the following statements about pseudogenes is FALSE?

Which of the following statements is TRUE?

Which of the following statements about retroviruses is FALSE?

The average size of a protein in a human cell is about 430 amino acids, yet the average gene in the human genome is 27,000 nucleotide pairs long.Explain.

Two individuals are represented in Figure 9-6; individual 1 is one of the parents of individual 2.The asterisk indicates the occurrence of a single mutation. Figure 9-6 What is the chance that individual 2 will inherit the mutation in individual 1?

Figure 9-7 shows an experiment used to determine the spontaneous mutation rate in E.coli.If the spontaneous mutation rate in E.coli is 1 mistake in every 10⁹ nucleotides copied, about how many colonies would you expect to see on the plates lacking histidine if you were to assay 10¹¹ cells from the culture for their ability to form colonies? Figure 9-7

Which of the following statements about gene families is FALSE?

For each of the following sentences, fill in the blanks with the best word or phrase in the list below.Not all words or phrases will be used; use each word or phrase only once. cellulose intron common neutral deleterious somatic gamete unequal homologous zygote Sexual reproduction in a multicellular organism involves specialized reproductive cells, called __________s, which come together to form a __________ that will divide to produce both reproductive and __________ cells.A point mutation in the DNA is considered a __________ mutation if it changes a nucleotide that leads to no phenotypic consequence; a point mutation is considered __________ if it changes a nucleotide within a gene and causes the protein to be nonfunctional.

There are about 700 eukaryotic genes that have obvious prokaryotic homologs.Would you predict that this set of genes would be enriched for genes that are used at distinct times during the life cycle of multicellular animals? Explain your answer.

Propose a reason to explain why highly repetitive regions of the genome are particularly susceptible to expansions and contractions in number.

Some retrotransposons and retroviruses integrate preferentially into regions of the chromosome that are packaged in euchromatin and are also located outside the coding regions of genes that contain information for making a protein.Why might these mobile genetic elements have evolved this strategy?

Which of the following would NOT be useful when finding genes in a newly sequenced mammalian genome?