Question 1

Which of the following can lead to transition mutations?

Accepted Answer

Both incorporation of a base analog and chemical modification of an existing base can lead to transition mutations by altering base-pairing properties.

Question 2

Mutations resulting from exposure to physical or chemical agents are called __________ mutations.

Accepted Answer

induced

Question 3

A __________ mutation does not alter the amino acid sequence of the resulting protein.

Accepted Answer

A silent mutation is a change in the DNA sequence that does not result in a change in the amino acid sequence of the protein. This is because the genetic code is redundant, meaning that different codons (triplets of nucleotides) can code for the same amino acid. Therefore, a change in the third nucleotide of a codon may not change the resulting amino acid.

Question 4

Spontaneous mutations are caused by

Accepted Answer

Spontaneous mutations can occur due to errors in DNA replication as well as insertion of transposons. Radiation can also cause mutations, but it is not limited to spontaneous mutations. Therefore, option E is not the best choice. Option B only includes the insertion of transposons, leaving out the possibility of errors in DNA replication, making it an incomplete choice. Option C is not sufficient as it only includes radiation as a cause of mutations. Hence, option D is the best choice as it includes both errors in DNA replication and insertion of transposons as potential causes of spontaneous mutations.

Question 5

A mutation that changes the amino acid sequence of the resulting protein by substitution is called a __________ mutation.

Accepted Answer

A missense mutation is a genetic change that alters the DNA sequence and leads to a different amino acid being incorporated into the resulting protein. This type of mutation can have a significant impact on the structure and function of the protein.

Question 6

Lethal mutations can be maintained in diploid organisms if they are

Accepted Answer

Lethal mutations can be maintained in diploid organisms if they are recessive. This is because in diploid organisms, there are two copies of each allele, one from each parent. If a recessive lethal mutation is present on one copy and the other copy is functional, the organism can still survive and pass on the mutated allele to its offspring. However, if the mutation is dominant, it will be expressed even if only one copy is present, and the organism will not survive to pass on the mutation. Deletions may or may not be lethal, depending on the specific genes affected.

Question 7

A mutation from the most prevalent form of a gene to a mutant form is called a __________ mutation.

Accepted Answer

A forward mutation changes the wild-type allele of a gene to a different form, typically resulting in a different phenotype or loss of function, contrasting with a reverse mutation, which would revert a mutant allele back to the wild-type.

Question 8

Mutations that result in the death of an organism when expressed are called __________ mutations.

Accepted Answer

Lethal mutations result in the death of an organism when expressed. Dominant and recessive mutations refer to the type of inheritance pattern, while conditional mutations require specific environmental or genetic conditions to be expressed.

Question 9

__________ are physical or chemical agents that cause mutation.

Accepted Answer

The answer of __________ are physical or chemical agents that...

Question 10

_______ are strains that are unable to grow on a minimal medium that supports growth of the wild type strain but are able to grow on the minimal medium if one or more nutritional supplements are added.

Accepted Answer

Auxotrophs are strains that are unable to synthesize certain essential nutrients, such as amino acids, and therefore require them to be provided in the growth medium. The ability to grow on minimal medium only when certain supplements are added indicates a lack of ability to synthesize those nutrients, making the strain an auxotroph.

Question 11

The __________ __________ is the most prevalent form of a gene in a population.

Accepted Answer

The answer of The __________ __________ is the most prevalent...

Question 12

Which of the following is considered a reverse mutation that will restore the wild type phenotype?

Accepted Answer

All the choices describe scenarios where the wild type phenotype is restored, either by reverting to the original sequence, altering the sequence to restore the original protein function, or restoring function through other means.

Question 13

Microbial strains that can grow on minimal medium are called __________.

Accepted Answer

Prototrophs are microbial strains that are able to grow on minimal medium, which only contains the basic nutrients required for growth, including carbon, nitrogen, phosphorus, and other vitamins and minerals. These strains are capable of synthesizing all of the organic molecules they need for growth from these basic nutrients, without requiring any additional supplements. In contrast, auxotrophs are microbial strains that require additional nutrients, such as specific amino acids, vitamins, or other compounds, to be provided in order to grow on minimal medium. Autotrophs are organisms that are capable of synthesizing all of their organic compounds from simple inorganic substances, such as carbon dioxide and water. Minitrophs is not a commonly used term in microbiology.

Question 14

__________ mutations occur in the promoter or operator region of a gene or set of genes and affects the expression of the downstream genes without affecting the amino acid sequences of the gene products.

Accepted Answer

The answer of __________ mutations occur in the promoter or...

Question 15

Which of the following types of mutation may play an important role in driving evolution because they are often nonlethal and, therefore, remain in the gene pool?

Accepted Answer

Missense mutations often only result in a change of a single amino acid in a protein, which may or may not affect its function. If the change is not severe enough to cause death or a significant disadvantage in survival, the mutation can remain in the gene pool and potentially spread through a population via genetic drift or natural selection. Nonsense and frameshift mutations often result in nonfunctional proteins, which can be lethal or severely disadvantageous and are therefore more likely to be eliminated from the gene pool. Deletions can have varying effects depending on their location and size.

Question 16

A mutagen that inserts between the stacked bases of a DNA double helix, distorting the DNA to induce single-pair insertions or deletions is called a(n) __________ agent.

Accepted Answer

Intercalating agents are mutagens that insert between the stacked bases of a DNA double helix, distorting the DNA to induce single-pair insertions or deletions. Therefore, the best choice is C - intercalating.

Question 17

A __________ mutation is one that causes premature termination of the synthesis of the protein product.

Accepted Answer

A nonsense mutation is a type of point mutation that causes a premature stop codon to be inserted into the DNA sequence, resulting in the premature termination of protein synthesis. This can lead to a truncated protein that is usually non-functional or unstable.

Question 18

__________ mutations affect only a single base pair in a gene.

Accepted Answer

The answer of __________ mutations affect only a single base...

Question 19

Lethal mutations can be recovered in haploid organisms if they are

Accepted Answer

Conditional mutations are only expressed under certain conditions, such as specific environmental factors or developmental stages. Therefore, they can be recovered in haploid organisms if these conditions are controlled or manipulated. Dominant mutations, on the other hand, are always expressed and cannot be recovered in haploid organisms. Active mutations and "none of the choices" are not relevant terms in this context.

Question 20

As the result of exposure to a mutagen, cytosine is substituted for thymine in one strand of DNA. Upon subsequent DNA replication, one of the daughter cells will have a GC pair in this position instead of an AT pair. This is called a(n) __________ mutation.

Accepted Answer

A substitution of one nucleotide for another is a point mutation. If the substitution involves a purine being replaced by a pyrimidine, or vice versa, this is called a transversion. If the substitution involves a purine being replaced by another purine, or a pyrimidine being replaced by another pyrimidine, this is called a transition. In this case, thymine (a pyrimidine) has been replaced by cytosine (another pyrimidine), making it a transition mutation. Frameshift mutations involve the insertion or deletion of nucleotides, while insertion mutations involve the addition of one or more nucleotides to the DNA sequence.

Quiz 14: Microbial Genetics Mechanisms of Genetic Variation