Question 1

Which feature of an organism would make it more suitable as a model organism?

Accepted Answer

If an organism is related to a large number of other organisms that exhibit some similarities, it is more likely that research conducted on the model organism will provide insight into a variety of other organisms. This makes it a better model organism.

Question 2

Which human gene would be most unusual?

Accepted Answer

Most human genes contain introns, so a gene completely lacking introns would be unusual. The presence of introns and the process of alternative splicing (choice C) are common in human genes. The length of a gene (choices A and B) can vary widely, and having four introns (choice D) is not uncommon in human genes.

Question 3

A piece of DNA that is about 6,500 nucleotides long is found in 10 to 30 locations (depending on the individual) throughout the genome of a fish.It uses an RNA intermediate and is both transcribed and translated.This element is most likely a(n)

Accepted Answer

The fact that this element uses an RNA intermediate and is both transcribed and translated indicates that it is a retrotransposon. The only retrotransposons listed as choices are LINEs, which can be several kilobases long and are found in multiple copies throughout the genome. RNA transposons are also retrotransposons, but they are typically smaller and found in fewer copies. DNA transposons do not use an RNA intermediate for transposition. SINEs (short interspersed nuclear elements) are also retrotransposons, but they are shorter (around 300 base pairs) and typically found in higher copy numbers than the described element. Short tandem repeats are repetitive sequences of 2-6 nucleotides and are not transposons.

Question 4

Which statement about pseudogenes is true?

Accepted Answer

Pseudogenes are non-functional copies of genes that have accumulated mutations that render them inactive. In some gene families, there appears to be little selection pressure for the deletion of pseudogenes, resulting in the proliferation of pseudogenes. Therefore, it is possible for gene families to have many pseudogenes. Option A is incorrect because the number of functional genes and pseudogenes in a gene family varies and could be equal. Option B is incorrect because pseudogenes can look very similar to functional genes. Option C is incorrect because pseudogenes generally arise from loss-of-function mutations rather than gain-of-function mutations. Option D is incorrect because gene families with pseudogenes may have many or few pseudogenes depending on the level of selection pressure.

Question 5

Butterflies use taste receptors to detect the presence of different foods.The receptors are encoded by genes in a gene family.Which circumstance would most likely lead to the evolution of pseudogenes in this gene family?

Accepted Answer

If there is a shift from feeding on many species to feeding on just one, it is likely that the taste receptors for the no-longer consumed foods will gradually become vestigial and eventually turn into pseudogenes. This is because mutations that render the receptors non-functional will no longer be selected against.

Question 6

In which aspect of the genome would you expect the most variation among different plant species?

Accepted Answer

Plants have evolved a variety of defenses against natural enemies, such as herbivores and pathogens, and these defenses can vary greatly between different species. Therefore, the genes involved with defenses against natural enemies would be the most variable among different plant species.

Question 7

The most likely reason why the plant Arabidopsis thaliana has more protein-coding genes than flies or nematodes have is that

Accepted Answer

The Arabidopsis genome contains many duplicated genes, which may contribute to the larger number of protein-coding genes compared to flies or nematodes. Duplications of genes can lead to specialized functions and a greater diversity of gene products. The other options (A, B, C, and E) do not necessarily contribute to an increase in protein-coding genes.

Question 8

Suppose a scientist engineered the mass movement of transposable elements in the genomes of a group of fruit flies, and then these flies had offspring.A control group of flies that were from the same genetic strain but had not had a mass movement of transposable elements also had offspring.The most likely result would be that the average survival rate of the experimental offspring would be _______ than that of the control offspring, and that the genetic variance in the experimental offspring would be _______ in the control offspring.

Accepted Answer

Transposable elements can introduce genetic mutations and variability. This increased genetic variance might lead to some offspring being less fit for survival, hence a potentially lower average survival rate. However, the genetic variance would be higher due to the introduced mutations and rearrangements in their genomes.

Question 9

Unlike LINEs, DNA transposons

Accepted Answer

DNA transposons do not use RNA intermediates in their transposition process, unlike LINEs (Long Interspersed Nuclear Elements) which do use RNA intermediates as part of their transposition mechanism.

Question 10

Short tandem repeats, commonly used in DNA fingerprinting, are an example of

Accepted Answer

Short tandem repeats (STRs) are highly repetitive DNA sequences used in DNA fingerprinting due to their variability among individuals.

Question 11

Because they are usually more sedentary than animals, plants generally require more

Accepted Answer

Plants require more genes involved in defense against natural enemies because they cannot move to escape threats and must rely on a variety of defense mechanisms to protect themselves from herbivores, pathogens, and environmental stresses.

Question 12

The human genome encodes about _______ proteins as it has protein-coding genes.

Accepted Answer

The answer of The human genome encodes about _______ proteins...

Question 13

Arabidopsis has a genome size much smaller than that of many other plants.What is the most likely explanation for this phenomenon?

Accepted Answer

The most likely explanation for Arabidopsis having a smaller genome size than many other plants is that it has less noncoding DNA. This means that it has a higher proportion of its DNA dedicated to coding for genes and performing essential functions, rather than having a large amount of noncoding or "junk" DNA. This is a common feature of many model organisms that are used in scientific research, as their smaller genomes are easier to study and manipulate than larger, more complex genomes.

Question 14

The evolution of gene families requires

Accepted Answer

The evolution of gene families requires gene duplications, where a single gene is duplicated to create a new copy. Over time, these duplicate genes may diverge in function or accumulate mutations, leading to the formation of a gene family. Pseudogenes, transposable elements, and repetitive sequences may also play a role in the evolution of gene families, but they are not essential requirements.

Question 15

Which feature ensures that in the human placenta, oxygen will be transferred from the mother's blood to the developing fetus's blood?

Accepted Answer

The fetal form of hemoglobin has a higher affinity for oxygen compared to the adult form, which allows efficient transfer of oxygen from the mother's blood to the fetus's blood in the placenta.

Question 16

The sequence ATGCT is repeated between 50 and 75 times (depending on the individual chromosome) in a row on a chromosome.It is not transcribed.This is an example of

Accepted Answer

Short tandem repeats (STRs) are sequences of DNA that are repeated in a row on a chromosome. The sequence ATGCT repeated between 50 and 75 times fits the definition of an STR because it is a short sequence repeated many times in tandem (next to each other) and is not transcribed.

Question 17

The genomes of most animals contain multiple identical copies of genes for rRNAs

Accepted Answer

The need for multiple copies of rRNA genes in most animal genomes is primarily because transcription of a single copy would be too slow to meet the cellular demand for ribosomal RNA, which is essential for protein synthesis.

Question 18

A pseudogene is

Accepted Answer

A pseudogene is a copy of a gene that has accumulated mutations over time, rendering it nonfunctional or unable to produce a protein with the same function as the original gene. It may have originated from a gene duplication event and then lost its functionality due to mutations. Pseudogenes are found in many genomes, including the human genome, as a result of the accumulation of mutations over millions of years of evolution.

Question 19

Which explanation is currently thought to be the best reason why transposable elements are so prevalent in eukaryotic genomes?

Accepted Answer

Transposable elements are prevalent in eukaryotic genomes primarily because they have the ability to replicate within the genome. This replication allows them to persist over generations, regardless of whether they confer a benefit, are neutral, or even deleterious to the organism. Their persistence is not necessarily because they provide a direct selective advantage to the organism in terms of gene regulation, genome integrity, or increasing genetic variation, but rather because of their inherent ability to replicate and thus maintain their presence in the genome.

Question 20

You are a researcher wanting to study cellular movement during animal development.An organism that had a transparent body would be ideal.What would be the best model organism to study?

Accepted Answer

Caenorhabditis elegans is a transparent roundworm that develops rapidly and has a well-understood cell lineage. This makes it an excellent model organism for studying cellular movement during animal development.

Quiz 17: Genomes