Question 1

Proteins can acquire new functions via

Accepted Answer

Gene duplication is a common mechanism for the evolution of new functions in proteins. When a gene undergoes duplication, the duplicate gene is free to accumulate mutations without affecting the function of the original gene. These mutations can result in changes to the protein sequence that lead to new functions or changes to the regulation of the gene that alter when and where the protein is produced. Other mechanisms, such as retrotransposons, biased gene conversion, and concerted evolution, can also involve changes to gene sequences, but they do not always result in the acquisition of new functions for proteins. Bioprospecting involves the search for new natural resources, including potential new protein functions, but it is not a mechanism for the evolution of proteins.

Question 2

Which of the following is not likely to occur after a gene duplication event?

Accepted Answer

It is unlikely for both genes to become pseudogenes after duplication, as this would result in a loss of function without any evolutionary advantage. Typically, at least one gene retains its function.

Question 3

Which of the following statements about genome evolution is true?

Accepted Answer

This statement is true, some salamanders have about 40 times as much DNA as humans do. The other statements are false or misleading. Humans have only about 2-3 times more genes than Drosophila, not 10-20 times more (A). While it is true that many species have more protein-coding genes than bacteria, the comparison of 500 times more is an exaggeration (B). A larger genome does not necessarily indicate greater complexity, as some organisms with simpler body plans can have larger genomes than more complex organisms (D).

Question 4

In a sequence of DNA taken from various species of snails, researchers have found that the rates of nonsynonymous substitutions and synonymous substitutions are roughly the same. What can we infer from this pattern?

Accepted Answer

If the rate of nonsynonymous substitutions and synonymous substitutions are roughly the same, it suggests that most of the amino-acid changes are neutral, meaning they are not positively or negatively selected for. This pattern is consistent with the neutral theory of molecular evolution, which posits that most mutations have little to no effect on an organism's fitness.

Question 5

Genes from many isolates of the influenza virus have been sequenced. In certain regions of the genome, nonsynonymous substitutions occur much more frequently than do synonymous substitutions. What can we infer from this pattern?

Accepted Answer

The pattern of nonsynonymous substitutions occurring more frequently than synonymous substitutions suggests that there is strong selection for change in this gene. This may be due to functional constraints or adaptation to changing environmental conditions.

Question 6

In which of the following would you expect the greatest extent of lateral gene transfer?

Accepted Answer

Bacteria have various mechanisms for transferring genetic material horizontally, such as transformation, transduction, and conjugation. These mechanisms make it easier for bacteria to acquire and incorporate genes from other organisms. In contrast, lateral gene transfer in plants, invertebrates, and vertebrates is much less common and more limited.

Question 7

Which of the following would be the strongest evi­dence that most noncoding DNA is slightly deleterious?

Accepted Answer

If most noncoding DNA is slightly deleterious, then it would accumulate more in populations with smaller effective sizes due to weaker selection. Therefore, species with smaller population sizes would have more noncoding DNA, making choice B the strongest evidence. Choices A and E do not necessarily provide evidence for the deleterious nature of noncoding DNA, while choices C and D do not address the issue of deleteriousness.

Question 8

In which of the following animals would you find the enzyme lysozyme?

Accepted Answer

Lysozyme is a widespread enzyme found in the secretions of many animals, including mammals, birds, reptiles, insects, and even some bacteria. It plays a role in the immune system by breaking down bacterial cell walls.

Question 9

Which of the following statements is true?

Accepted Answer

Large genomes can slow down development because they require more time and energy to replicate and regulate during development. Selection against the accumulation of junk DNA is not necessarily more effective in species with small populations, and noncoding sequences are not typically thought to be advantageous.

Question 10

Which of the following are foregut fermenters?

Accepted Answer

Both langurs and cattle are known to be foregut fermenters, while lemurs are not.

Question 11

Some birds have an enlarged esophageal chamber called a

Accepted Answer

The enlarged esophageal chamber in some birds is called a crop. The other options (hoatzin, tranversion, locazen, vulva) are not related to a bird's enlarged esophageal chamber.

Question 12

Which of the following statements about genomes is true?

Accepted Answer

None of the statements are true. Some plants have larger genomes than some animals, but it varies widely within each group. Humans do not have the largest genome size of all animals; lungfish, for example, have much larger genomes. While bacterial genomes are typically smaller than those of eukaryotic organisms, much of the bacterial genome codes for functional genes.

Question 13

Researchers suspect that the gene FOXP2, which is involved in speech and cognition, has been under positive selection in the human lineage. Which of the following would provide the strongest support for such a claim?

Accepted Answer

A higher rate of nonsynonymous substitutions (changes in the DNA sequence that result in a different amino acid being encoded) compared to synonymous substitutions (changes that do not change the amino acid) suggests that the gene is under positive selection, as natural selection is favoring changes that result in a different protein sequence. This provides strong evidence that FOXP2 has been under positive selection in the human lineage as it is involved in speech and cognition.

Question 14

Histones are proteins that play important roles in gene regulation. Between plants and animals, only two amino acid changes have occurred in the histone H4 protein, despite many synonymous changes. What can we infer from this observation?

Accepted Answer

The fact that there have only been two amino acid changes despite many synonymous changes suggests that there is strong stabilizing selection acting on this gene. This means that mutations in the amino acid sequence of histone H4 are not well tolerated and may disrupt its important roles in gene regulation.

Question 15

The best way to detect whether lateral gene transfer has occurred would be by

Accepted Answer

Looking for genes whose phylogenies differ from that of most of the genes would be the best way to detect whether lateral gene transfer has occurred. This is because in lateral gene transfer, a gene from one organism is transferred to another organism, resulting in a phylogeny that is different from the overall evolutionary history of the organism. Therefore, by identifying such genes with different phylogenies, one can detect potential instances of lateral gene transfer.

Question 16

The human genome contains _______ genes.

Accepted Answer

The human genome contains between 15,000 and 30,000 genes.

Question 17

Which of the following were used by investigators to study the loss of genetic material in different insects?

Accepted Answer

Retrotransposons are mobile genetic elements that can move within genomes and cause changes in gene expression. They have been widely used as molecular markers to study genetic diversity, population structure, and evolutionary relationships among different insect species.

Question 18

Which of the following statements about genomes is true?

Accepted Answer

The variation in genome size among animals is indeed greater than the variation in the number of genes, due to non-coding DNA. Most of the human genome does not code for proteins.

Question 19

Which of the following statements about lysozymes is false?

Accepted Answer

This statement is false as lysozymes have functions in mammals that are not foregut fermenters, such as in antibacterial defense.

Question 20

One reason that crickets (Laupala) have a larger genome size than fruit flies (Drosophila) is that crickets

Accepted Answer

Crickets lose DNA more slowly than fruit flies, which contributes to their larger genome size.

Quiz 24: Evolution of Genes and Genomes

Proteins can acquire new functions via

Which of the following is not likely to occur after a gene duplication event?

Which of the following statements about genome evolution is true?

In a sequence of DNA taken from various species of snails, researchers have found that the rates of nonsynonymous substitutions and synonymous substitutions are roughly the same. What can we infer from this pattern?

Genes from many isolates of the influenza virus have been sequenced. In certain regions of the genome, nonsynonymous substitutions occur much more frequently than do synonymous substitutions. What can we infer from this pattern?

In which of the following would you expect the greatest extent of lateral gene transfer?

Which of the following would be the strongest evidence that most noncoding DNA is slightly deleterious?

In which of the following animals would you find the enzyme lysozyme?

Which of the following statements is true?

Which of the following are foregut fermenters?

Some birds have an enlarged esophageal chamber called a

Which of the following statements about genomes is true?

Researchers suspect that the gene FOXP2, which is involved in speech and cognition, has been under positive selection in the human lineage. Which of the following would provide the strongest support for such a claim?

Histones are proteins that play important roles in gene regulation. Between plants and animals, only two amino acid changes have occurred in the histone H4 protein, despite many synonymous changes. What can we infer from this observation?

The best way to detect whether lateral gene transfer has occurred would be by

The human genome contains _______ genes.

Which of the following were used by investigators to study the loss of genetic material in different insects?

Which of the following statements about genomes is true?

Which of the following statements about lysozymes is false?

One reason that crickets (Laupala) have a larger genome size than fruit flies (Drosophila) is that crickets

Quiz 24: Evolution of Genes and Genomes

Proteins can acquire new functions via

Which of the following is not likely to occur after a gene duplication event?

Which of the following statements about genome evolution is true?

In a sequence of DNA taken from various species of snails, researchers have found that the rates of nonsynonymous substitutions and synonymous substitutions are roughly the same. What can we infer from this pattern?

Genes from many isolates of the influenza virus have been sequenced. In certain regions of the genome, nonsynonymous substitutions occur much more frequently than do synonymous substitutions. What can we infer from this pattern?

In which of the following would you expect the greatest extent of lateral gene transfer?

Which of the following would be the strongest evi­dence that most noncoding DNA is slightly deleterious?

In which of the following animals would you find the enzyme lysozyme?

Which of the following statements is true?

Which of the following are foregut fermenters?

Some birds have an enlarged esophageal chamber called a

Which of the following statements about genomes is true?

Researchers suspect that the gene FOXP2, which is involved in speech and cognition, has been under positive selection in the human lineage. Which of the following would provide the strongest support for such a claim?

Histones are proteins that play important roles in gene regulation. Between plants and animals, only two amino acid changes have occurred in the histone H4 protein, despite many synonymous changes. What can we infer from this observation?

The best way to detect whether lateral gene transfer has occurred would be by

The human genome contains _______ genes.

Which of the following were used by investigators to study the loss of genetic material in different insects?

Which of the following statements about genomes is true?

Which of the following statements about lysozymes is false?

One reason that crickets (Laupala) have a larger genome size than fruit flies (Drosophila) is that crickets

Which of the following would be the strongest evidence that most noncoding DNA is slightly deleterious?