Question 1

Griffith's observations from his experiments infecting mice with smooth and rough strain Streptococcus pneumoniae were later found to be due to

Accepted Answer

Griffith's observations were due to transformation, which is the process of uptake and incorporation of DNA from the external environment.

Question 2

What specifically is passed from the donor cell to the recipient cell during conjugation?

Accepted Answer

During bacterial conjugation, single-stranded DNA is passed from the donor cell to the recipient cell. This process is facilitated by the F factor (fertility factor), which allows the formation of a conjugation pilus, but it is the DNA that is actually transferred, not the pilus itself.

Question 3

Why might an organism transform DNA that is homologous to its own?

Accepted Answer

Transforming homologous DNA can be one way for an organism to repair its own damaged genome. This process, called homologous recombination, allows for the integration of new, undamaged DNA into the existing genome, potentially repairing mutations or breaks in the DNA.

Question 4

Examine the figure shown.What happened to transform the original MRSA isolate into the small-colony variant?

Accepted Answer

The transformation of the original MRSA isolate into the small-colony variant was likely due to natural selection. The small-colony variant may have had a genetic mutation that allowed it to survive and replicate better in its environment, leading to its increased prevalence. This is an example of natural selection at work, where the most advantageous traits are selected for over time through the process of evolution.

Question 5

Which of the following forms of horizontal gene transfer involves a prophage?

Accepted Answer

Specialized transduction involves a prophage, which is a phage DNA that has integrated into the bacterial chromosome. During specialized transduction, the phage DNA excises from the bacterial chromosome and takes some of the adjacent bacterial DNA with it. This DNA is then packaged into phage particles and can be transferred to a new host cell in the same manner as generalized transduction. However, specialized transduction is more specific than generalized transduction because it only transfers a specific set of bacterial genes that are located near the site of prophage integration.

Question 6

Examine the figure shown.Which of the following correctly describes how the two organisms pictured would fare if grown in an environment without antibiotics?

Accepted Answer

Based on the figure, we can see that the small-colony variant has a mutation that makes it unable to produce as much pigment as the original isolate. Since pigment production is energetically costly for the bacteria, the small-colony variant may have an advantage in environments where resources are limited. However, this advantage may come at a cost of decreased virulence or reduced ability to compete with other bacteria. In an environment without antibiotics, the small-colony variant may still have a slight advantage over the original isolate, but it is likely that the original isolate would outcompete the small-colony variant due to its higher degree of virulence and competitiveness. Therefore, choice C is correct. The other choices are incorrect because there is no evidence to suggest that the small-colony variant would outcompete or grow better than the original isolate, and it is unlikely that neither organism would grow in an environment without antibiotics.

Question 7

Without selective pressure,a species is at risk of experiencing

Accepted Answer

Without selective pressure, a species may undergo reductive evolution, where it loses traits that are no longer necessary. There is no pressure for the species to maintain these traits, so they may be lost over time. Random mutation alone does not necessarily lead to significant changes in a species, while natural selection requires selective pressure. Endosymbiosis is a process by which one organism lives inside another, so it is not directly related to the absence of selective pressure.

Question 8

What is most important for determining the fitness of one organism versus another?

Accepted Answer

The environment is the most important factor in determining the fitness of one organism versus another because it directly influences which traits are advantageous for survival and reproduction. Organisms best adapted to their current environment are more likely to survive, reproduce, and pass on their genes.

Question 9

The elements that form living organisms first originated from

Accepted Answer

The elements that form living organisms originated from stardust as they were created during the birth and death of stars through processes such as fusion and supernovae explosions. These elements eventually formed planets, including Earth, where life emerged. While water and the oceans are important for the survival of living organisms, they are not the origin of the elements that make up life. Viruses are not considered living organisms, and while they may contain some of the same elements as living organisms, they do not play a role in their origin.

Question 10

Which of the following does NOT lead to divergence?

Accepted Answer

Fossilization does not lead to divergence as it refers to the preservation of past genetic characteristics rather than the creation of new genetic variations. Mutations, transposition, and transduction can lead to divergence by introducing novel genetic variations into a population.

Question 11

Which of the following is NOT a good scenario for a molecular clock?

Accepted Answer

The molecular clock relies on neutral mutations that accumulate over time, so using a gene that is nonessential could lead to different mutation rates and skew the results.using essential genes as a clock can be problematic, as natural selection may maintain certain sequences despite time, thus obscuring the clock-like signal. The other three options (A, B, and C) are all ideal scenarios for a molecular clock.

Question 12

Which of the following domains of life contain ether linkages in their membranes?

Accepted Answer

Ether linkages are present in the membranes of archaea. This is a characteristic feature of archaeal membranes which distinguish them from bacterial and eukaryotic membranes that contain ester linkages.

Question 13

Meaningful evolution occurs when

Accepted Answer

The answer of Meaningful evolution occurs when
...

Question 14

Why can antibiotics be used to treat the nematode cause of filarial disease?

Accepted Answer

Antibiotics can be used to treat the nematode cause of filarial disease because they target the endosymbiotic bacteria, Wolbachia, that is essential for the embryonic development, survival, and reproduction of the filarial worm. When Wolbachia is eliminated, the worm cannot develop properly and will eventually die. This makes antibiotics a promising treatment option for filarial diseases, such as lymphatic filariasis and onchocerciasis, which affect millions of people worldwide.

Question 15

Wolbachia appears to be developing into a(n)________ of its host.

Accepted Answer

The answer of Wolbachia appears to be developing into a(n)________...

Question 16

Examine the figure shown.Which organism does NOT share the same common ancestor as Escherichia and Erwinia carotovora?

Accepted Answer

The answer of Examine the figure shown.Which organism does NOT...

Question 17

If the mutation rate is not the same for all species being compared using a molecular clock,what does a phylogenetic tree demonstrate?

Accepted Answer

A phylogenetic tree, when the mutation rate varies across species, primarily demonstrates the evolutionary distance between species rather than precise divergence times. This is because the molecular clock assumption (constant mutation rate) is violated, making it difficult to accurately infer time since divergence.

Question 18

Which of the following is NOT a step in the transduction process?

Accepted Answer

Transduction involves the transfer of DNA from one bacterium to another by a virus (phage). The process described in choice A, where a DNA phage enters a bacterial cell by endocytosis, is not accurate for bacteriophages. Bacteriophages typically inject their DNA into the bacterial cell rather than entering through endocytosis.

Question 19

A protein called integrase is encoded by ________ and allows for site-specific recombination in C.diphtheria.

Accepted Answer

The answer of A protein called integrase is encoded by...

Question 20

How do bacteria protect their own DNA from restriction enzymes?

Accepted Answer

Bacteria protect their own DNA from restriction enzymes by adding a methyl group to the target sequence recognized by the enzyme, which prevents it from cutting the DNA. This process is known as methylation.

Quiz 9: Bacterial Genomes and Evolution