Question 1

Horizontal DNA transfer may make it more difficult to construct phylogenetic trees.

Accepted Answer

Horizontal gene transfer, also called lateral gene transfer, is the movement of genetic material between different organisms that are not parent and offspring. This can make it more difficult to construct phylogenetic trees because it can lead to the sharing of genetic traits that would normally be used to distinguish the evolutionary history of different organisms. Horizontal gene transfer is particularly common among bacteria and other microorganisms, which can exchange plasmids and other mobile genetic elements that carry genes for antibiotic resistance, metabolic pathways, and other traits.

Question 2

The three domain systems consist of Archaea, Bacteria, Eucarya.

Accepted Answer

The three domain systems are indeed Archaea, Bacteria, and Eucarya.

Question 3

Sequencing of rRNA is useful for

Accepted Answer

Sequencing of rRNA is useful for both determining evolutionary relationships and identification of unknown bacteria. By comparing the sequence of rRNA from different organisms, scientists can determine how closely related they are and how they evolved over time. Additionally, since the sequence of rRNA is unique to different species of bacteria, it can be used as a tool for identifying unknown organisms.

Question 4

Disagreements between conclusions obtained from rDNA data and other techniques may be explained by

Accepted Answer

Horizontal DNA transfer can introduce differences in genetic information between organisms that were not inherited vertically, which can cause discrepancies between rDNA data and other techniques.

Question 5

A DNA similarity of 75% between two organisms

Accepted Answer

The answer of A DNA similarity of 75% between two...

Question 6

Why might it be easier to determine the bacterium that caused pneumonia than one that caused a wound infection?

Accepted Answer

The skin has numerous types of bacteria on it, which may interfere with the process of identifying the particular bacterium responsible for a wound infection. The lungs, however, are generally free of bacteria, making it easier to attribute pneumonia to a specific microorganism.

Question 7

Numerical taxonomy uses a battery of genotypic characteristics to classify bacteria.

Accepted Answer

Numerical taxonomy uses a wide range of phenotypic characteristics, not genotypic, to classify bacteria.

Question 8

Serratia marcescens are red when incubated at 37°C.

Accepted Answer

Serratia marcescens produces a red pigment called prodigiosin at temperatures below 30°C; at 37°C, typically used for incubation in laboratories, the bacteria do not produce the pigment and thus do not appear red.

Question 9

If the GC content of two organisms is 45% in both

Accepted Answer

The GC content alone cannot determine whether two organisms are related or not as it is a common feature in many different organisms. Further analysis is needed to determine if they are related or not. Also, the AT content cannot be inferred solely from the GC content without additional information.

Question 10

rRNA sequence comparisons are useful for determining evolutionary relationships.

Accepted Answer

rRNA sequences are highly conserved and evolve slowly, making them useful for determining the evolutionary relationships between organisms. By comparing the differences and similarities in rRNA sequences, scientists can construct phylogenetic trees and understand the evolutionary history of different species.

Question 11

If each of two bacteria have a %GC of 50%, this means that they are both definitely closely related.

Accepted Answer

While a %GC of 50% may indicate similarity in the nucleotide content, it does not necessarily mean that the bacteria are closely related. Other factors such as gene content and morphology should also be taken into consideration.

Question 12

Phylogenetic relationships between prokaryotes are most accurately determined using

Accepted Answer

Genotypic information, such as sequencing of ribosomal RNA genes, provides a more accurate representation of evolutionary relationships between prokaryotes than phenotypic characteristics, which can be influenced by environmental factors. The fossil record is not always available for prokaryotes due to their typically small size and lack of hard parts. Carbon dating is not applicable as it is used for determining the age of organic materials, not for determining evolutionary relationships.

Question 13

All known species of bacteria are described in Bergey's Manual of Systematic Bacteriology.

Accepted Answer

The answer of All known species of bacteria are described...

Question 14

A sample must contain many microorganisms in order to see any using microscopy techniques. Why?

Accepted Answer

The area on a microscope slide is much larger than the size of individual microbes, so in order to increase the chances of seeing them, a large number of microbes must be present in the sample initially.

Question 15

Streptococcus pyogenes can be easily distinguished microscopically from other Streptococcus species.

Accepted Answer

Streptococcus pyogenes cannot be easily distinguished microscopically from other Streptococcus species, and further laboratory testing is required to identify it.

Question 16

When DNA probes are used to identify bacterial DNA similarities by hybridization, the probe DNA is heated and the template DNA is treated to separate the 2 strands. Why would the probe DNA be heated?

Accepted Answer

The probe DNA is heated to break any possible hydrogen bonds that may have formed, returning it to a single-stranded state prior to hybridization. This ensures that the probe can properly hybridize with the complementary strands of the bacterial template DNA.

Question 17

Why are molecular methods particularly useful for identification of microbes when they are difficult to grow?

Accepted Answer

Molecular methods can detect and identify microbes even when they cannot be grown in culture, by detecting even very small amounts of their DNA. This makes them particularly useful for identifying difficult-to-culture microbes. Option A is incorrect because molecular methods are not always faster than culturing microbes, and sometimes culturing is necessary for full identification. Option B is incorrect because there are some microbes that are notoriously difficult to culture, making molecular methods indispensable. Option D is incorrect because molecular methods can often be more expensive than culturing, depending on the specific technique used.

Question 18

Explain the difference between a biotype and a serotype.

Accepted Answer

A biotype refers to the biochemical profile or set of phenotypic traits of a microorganism, while a serotype refers to the different surface structures/antigens (such as proteins or sugars) that can elicit separate immune responses from an individual, characterized by the presence of different antibodies in the individual's serum.

Question 19

Size and shape may allow one to differentiate between a bacterium, fungus, or protozoan.

Accepted Answer

Different microbial groups (bacteria, fungi, protozoa) have different cellular structures and types, leading to differences in size and shape that can be used for identification purposes.

Question 20

Based on DNA hybridization, humans and chimpanzees are the same species.

Accepted Answer

The answer of Based on DNA hybridization, humans and chimpanzees...

Quiz 10: Identification and Classification of Prokaryotes