Question 1

The comparison of the amino acid sequences of cytochrome c (see Figure 24.3) from plants to human showed that

Accepted Answer

The comparison of the amino acid sequences of cytochrome c from plants to humans showed that gaps and/or insertions were required in some cases to optimize the alignment. This implies that the sequences were not identical and some editing was required to align them properly.

Question 2

Gene duplication can

Accepted Answer

Gene duplication can occur through various mechanisms, including duplication of an entire genome (A). It can lead to the formation of pseudogenes when duplicated genes accumulate mutations and lose function (B). Some duplicated genes may be lost over time if they are not beneficial (C). Additionally, gene duplication can provide raw material for evolution, allowing one copy to maintain its original function while the other acquires mutations that may lead to new functions (D). Therefore, all options are correct.

Question 3

Mistakes in the replication of DNA

Accepted Answer

Mistakes in DNA replication can lead to genetic variation, which is important for evolution and adaptation. Some mistakes may be beneficial, while others may be detrimental.

Question 4

Synonymous mutations of a gene

Accepted Answer

Synonymous mutations do not change the amino acid sequence of a protein, so they are neutral with respect to the fitness of an organism. They are also favored when there is strong stabilizing selection, which means that the organism is under strong pressure to maintain the current amino acid sequence of the protein.

Question 5

Ribosomal RNA genes

Accepted Answer

Ribosomal RNA genes undergo concerted evolution, which means that copies of the genes within an individual organism and within a population evolve in a coordinated manner, leading to higher sequence similarity between copies than would be expected by chance. This is due to homogenization mechanisms like unequal crossing over and gene conversion.

Question 6

Which of the following statements about synonymous mutations is true?

Accepted Answer

Synonymous mutations are changes in the DNA sequence that do not result in a different amino acid being translated. They occur because of the redundancy of the genetic code, which allows for multiple codons to code for the same amino acid. Therefore, choice B is the correct statement. The other answer choices are incorrect because synonymous mutations do not change the amino acid composition of the protein (choice A), affect the structure of the protein (choice C), change the activity of the protein (choice D), or be lethal (choice E).

Question 7

How is the study of molecular evolution important in efforts to combat HIV and other viral pathogens that have recently emerged?

Accepted Answer

The answer of How is the study of molecular evolution...

Question 8

The experiments of Rainey and Travisano with Pseudomonas fluorescens showed that

Accepted Answer

The experiments showed that certain mutations were beneficial to the bacterium under one condition, but harmful under another. This demonstrates that the environment plays a significant role in determining the success of a particular genotype or phenotype.

Question 9

In the amino acid sequences shown in Figure 24.1, position(s) _______ are conserved and positions _______ shows the most variation in amino acid identity. The amino acids are labeled sequentially from left to right.

Accepted Answer

By comparing the amino acid sequences, we can see that positions 1, 4, and 7 are conserved, meaning that the same amino acid is found in those positions across all species. On the other hand, position 5 shows the most variation in amino acid identity, with different amino acids found in that position across different species. Therefore, the best choice is D as it correctly identifies both the conserved positions and the position with the most variation.

Question 10

Refer back to Figure 14.6 to answer this question. Which of the following nucleotide substitutions in a codon in a gene that codes for a protein would likely have the most harmful affect on the activity of the protein?

Accepted Answer

The nucleotide substitution in choice B changes the codon from encoding the amino acid serine (S) to a stop codon (UGA), which would result in premature termination of the protein and likely lead to a nonfunctional or severely impaired protein.

Question 11

A eukaryotic organism's genome

Accepted Answer

A eukaryotic organism's genome consists of all of the genes as well as noncoding regions of DNA. This includes introns, regulatory sequences, and other non-coding elements in addition to the protein-coding genes.

Question 12

Gene families are groups of _______ genes that arose by _______ and _______.

Accepted Answer

Gene families are groups of homologous genes, meaning they share a common ancestor. These genes arise through gene duplication events, where a copy of a gene is made in the genome. Over time, the duplicated gene may experience mutations that alter its function, resulting in the evolution of new genes within the family.

Question 13

Refer to Figure 24.12. Which of the following statements about this figure is false?

Accepted Answer

The answer of Refer to Figure 24.12. Which of the...

Question 14

A mutation in a gene in which an A is changed to a G is called a _______ whereas a mutation of A to T is called a _______. The former type of mutation occurs at a _______ frequency than the latter.

Accepted Answer

A mutation in which a purine (A or G) is changed to another purine (A or G) is called a transition, while a mutation in which a purine is changed to a pyrimidine (T or C) or vice versa is called a transversion. Therefore, a mutation of A to G is a transition, and a mutation of A to T is a transversion. Transition mutations occur at a higher frequency than transversion mutations because they are caused by a single-nucleotide base change, whereas transversion mutations require a substitution between two different nucleotide classes.

Question 15

The alignment of the amino acid sequences of a protein from different species

Accepted Answer

The alignment of amino acid sequences of a protein from different species may be complicated by the presence of insertions, and it can be used to calculate evolutionary divergence. Thus, both option A and D are correct, making option E the best choice. Option B is incorrect because the total number of substitutions cannot always be determined solely through sequence alignment. Option C is incorrect because different proteins evolve at different rates, so amino acid sequence alignment cannot be used as a general molecular clock.

Question 16

Comparisons of the genes that code for lysozyme and the amino acid sequence of the enzyme from a number of organisms revealed that

Accepted Answer

The answer of Comparisons of the genes that code for...

Question 17

Which of the following statements about the genomes of organisms is false?

Accepted Answer

The total size of the genome of eukaryotes varies greatly from organism to organism. For example, the human genome is about three times larger than the genome of the pufferfish.

Question 18

A neutral mutation

Accepted Answer

A neutral mutation is not subject to selection and is fixed in a population at a rate equal to the mutation rate according to the neutral theory of molecular evolution.

Question 19

Genes found in different species that diverge as a result of speciation are called _______, whereas genes in the same or different organism that arise by gene duplication are called _______.

Accepted Answer

The genes that arise as a result of speciation, meaning they existed in a common ancestor but diverged through the process of evolution, are called orthologs. On the other hand, when genes are duplicated within an organism or between different organisms, they are called paralogs. Therefore, the correct answer is C: orthologs are genes found in different species that diverge as a result of speciation, while paralogs are genes in the same or different organism that arise by gene duplication.

Question 20

Nonsynonymous mutations in a gene coding for a protein

Accepted Answer

Nonsynonymous mutations can result in the replacement of an amino acid in the protein, which can result in changes in the protein's structure and function. Depending on the location and nature of the mutation, it may be neutral, deleterious, or beneficial. Therefore, all of the answer choices are correct.

Quiz 24: Evolution of Genes and Genomes