Question 1

Addition or deletion of one or two nucleotides in the coding part of a gene produces a nonfunctional protein, whereas addition or deletion of three nucleotides often results in a protein with nearly normal function. Explain.

Accepted Answer

The answer of Addition or deletion of one or two...

Question 2

What is unique about RNA tumor viruses (retroviruses) that allows their RNA genome to be replicated and inserted as DNA into host cells?

Accepted Answer

The answer of What is unique about RNA tumor viruses...

Question 3

EcoRI restriction mapping on a sample of a large piece of DNA resulted in six distinct bands following agarose gel electrophoresis. Similar mapping on an identical sample that was subjected to high intensity ultraviolet light resulted in only four distinct bands. What might best explain the reduction in the number of detectable bands in the UV light-treated sample?

Accepted Answer

The answer of EcoRI restriction mapping on a sample of...

Question 4

Why are dideoxynucleotides used in DNA sequencing?

Accepted Answer

The answer of Why are dideoxynucleotides used in DNA sequencing?...

Question 5

If a plasmid does not contain an origin of replication, what would happen if you were to transfect it into bacteria?

Accepted Answer

The answer of If a plasmid does not contain an...

Question 6

Suppose you have a cell line that expresses a protein whose structure you know but not the function. Describe an experiment that would help you determine the protein's function.

Accepted Answer

The answer of Suppose you have a cell line that...

Question 7

Suppose you have a cell line that expresses a protein whose structure you know but not the function. You use RNA interference to block expression of the protein. How could you confirm that the interference was effective?

Accepted Answer

The answer of Suppose you have a cell line that...

Question 8

Which statement correctly represents the distinction between the terms "genotype" and "phenotype"?
A) Phenotype is the genetic composition of an organism, and genotype is the physical appearance.
B) There is no difference between a genotype and a phenotype.
C) A phenotype is dominant, and a genotype is recessive.
D) The genotype is the genetic composition of an organism, and the phenotype is its physical appearance.

Accepted Answer

The genotype refers to the genetic makeup of an organism, while the phenotype refers to its physical traits and characteristics. In other words, the genotype is the set of inherited genes that determine specific traits, and the phenotype is the observable expression of those genes.

Question 9

In Gregor Mendel's experiments on pea genetics, he determined that yellow seed color, Y, was dominant over green seed color, y. In a cross between two plants, one with yellow seeds and the other with green seeds, all the seeds produced from the offspring were yellow. What was the genotype of the parent plant with yellow seeds?
A) YY
B) Yy
C) yY
D) yy

Accepted Answer

Since all of the offspring had yellow seeds, the parent with yellow seeds must have been homozygous dominant (YY). If it was heterozygous (Yy), there would have been a 50% chance for green seeds in the offspring. If it had been homozygous recessive (yy), all the offspring would have had green seeds.

Question 10

The two strands of DNA in the double helix are held together by
A) interactions between the sugar residues of each chain.
B) interactions between phosphate residues of each strand.
C) hydrogen bonds between the bases of each strand.
D) covalent bonds between the bases of each strand.

Accepted Answer

The two strands of DNA in the double helix are held together by hydrogen bonds between the nitrogenous bases. These bases include adenine (A), thymine (T), cytosine (C), and guanine (G), and they always pair in the same way: A with T and C with G. The hydrogen bonds between these complementary base pairs are relatively weak, allowing the strands to separate during DNA replication and transcription.

Question 11

The process by which proteins are made from RNA templates is called
A) transcription.
B) translation.
C) transposition.
D) interpretation.

Accepted Answer

The process by which proteins are made from RNA templates is called translation. Transcription is the process by which RNA is synthesized from DNA, while transposition is the movement of genetic material within a genome. Interpretation is not a term commonly used to describe this process.

Question 12

Which molecule serves as an adaptor between amino acids and mRNA during translation?
A) rRNA
B) DNA
C) tRNA
D) siRNA

Accepted Answer

tRNA (transfer RNA) serves as an adaptor between amino acids and mRNA by recognizing the codon (a sequence of three nucleotides) on mRNA and bringing the correct amino acid to the growing protein chain during translation.

Question 13

The enzyme that synthesizes DNA using RNA templates is called
A) DNA polymerase.
B) RNA polymerase.
C) ribozymes.
D) reverse transcriptase.

Accepted Answer

The enzyme that synthesizes DNA using RNA templates is called reverse transcriptase. This enzyme is found in retroviruses, which have RNA as their genetic material and use reverse transcriptase to convert their RNA into DNA for integration into the host cell's genome.

Question 14

A restriction enzyme with a four-base recognition site would cleave DNA with a statistical frequency of once every
A) 4 base pairs.
B) 256 base pairs.
C) 4,096 base pairs.
D) 65.5 kilobases.

Accepted Answer

A four-base recognition site means that the enzyme will only cut when it encounters a specific sequence of four nucleotides. There are 4 possible nucleotides (A, T, C, G), so the probability of finding a specific four-nucleotide sequence is 1/4^4, or 1/256. Therefore, the enzyme will cleave DNA with a statistical frequency of once every 256 base pairs.

Question 15

Why can't a digest of human genomic DNA be resolved by gel electrophoresis?
A) Once cut by the restriction enzyme, the fragments are unstable
B) A typical digest of the human genome produces too many fragments to resolve
C) The fragments will be too large to move through the gel
D) The fragments will all be the same size

Accepted Answer

A typical digest of the human genome with restriction enzymes produces millions of fragments, making it impossible to resolve individual bands on a gel electrophoresis. This results in a smear rather than distinct bands.

Question 16

The characterization of restriction endonucleases was a key step in the development of recombinant DNA technology. What is the function of these enzymes?
A) Synthesis of complementary strands of DNA from a DNA template
B) Synthesis of RNA from a DNA template
C) Ligation of two digested DNA strands
D) Cleavage of DNA at specific sequences

Accepted Answer

Restriction endonucleases cleave DNA at specific sequences, which is important in recombinant DNA technology for cutting and manipulating DNA fragments.

Question 17

Which character is not necessary in a plasmid vector to facilitate successful cloning?
A) Origin of replication
B) Gene conferring resistance to antibiotic
C) Restriction site
D) Strong bacterial promoter

Accepted Answer

The origin of replication is necessary for plasmid replication, the gene conferring resistance to antibiotic is useful for the selection of transformed bacteria, and the restriction site(s) allow for the insertion of foreign DNA into the plasmid. However, the presence of a strong bacterial promoter is not necessary for successful cloning as it only serves to drive expression of the inserted DNA in the bacteria.

Question 18

A cDNA molecule is
A) DNA synthesized from an RNA template using the enzyme reverse transcriptase.
B) the nucleic acid portion of a ribosome.
C) a DNA molecule capable of independent replication in a host cell.
D) RNA or single-stranded DNA, complementary to the mRNA of a gene of interest, that hybridizes with the mRNA and blocks its translation.

Accepted Answer

A cDNA molecule is synthesized from an RNA template using the enzyme reverse transcriptase. This allows for the conversion of RNA into DNA, which can be useful in studying gene expression and genetic manipulation.

Question 19

A PCR reaction does not require
A) a heat stable DNA polymerase.
B) DNA containing the sequence to be amplified.
C) short single stranded DNA primers complementary to each end of the target sequence.
D) sodium dodecyl sulfate.

Accepted Answer

Sodium dodecyl sulfate (SDS) is a detergent often used in protein extraction, but it is not necessary for a PCR reaction. The other choices (heat stable DNA polymerase, DNA template, and primers) are all essential components of a PCR reaction.

Question 20

How many molecules would be produced from two molecules of DNA following five rounds of PCR amplification?
A) 10
B) 32
C) 64
D) One billion

Accepted Answer

Each round of PCR doubles the number of DNA molecules. After 5 rounds, the number of copies is 2 to the power of 5, which equals 32. Therefore, 64 molecules of DNA would be produced (since two starting molecules were used).

Quiz 4: Fundamentals of Molecular Biology

Addition or deletion of one or two nucleotides in the coding part of a gene produces a nonfunctional protein, whereas addition or deletion of three nucleotides often results in a protein with nearly normal function. Explain.

What is unique about RNA tumor viruses (retroviruses) that allows their RNA genome to be replicated and inserted as DNA into host cells?

Why are dideoxynucleotides used in DNA sequencing?

If a plasmid does not contain an origin of replication, what would happen if you were to transfect it into bacteria?

Suppose you have a cell line that expresses a protein whose structure you know but not the function. Describe an experiment that would help you determine the protein's function.

Suppose you have a cell line that expresses a protein whose structure you know but not the function. You use RNA interference to block expression of the protein. How could you confirm that the interference was effective?

Which statement correctly represents the distinction between the terms "genotype" and "phenotype"?

The two strands of DNA in the double helix are held together by

The process by which proteins are made from RNA templates is called

Which molecule serves as an adaptor between amino acids and mRNA during translation?

The enzyme that synthesizes DNA using RNA templates is called

A restriction enzyme with a four-base recognition site would cleave DNA with a statistical frequency of once every

Why can't a digest of human genomic DNA be resolved by gel electrophoresis?

The characterization of restriction endonucleases was a key step in the development of recombinant DNA technology. What is the function of these enzymes?

Which character is not necessary in a plasmid vector to facilitate successful cloning?

A cDNA molecule is

A PCR reaction does not require

How many molecules would be produced from two molecules of DNA following five rounds of PCR amplification?