Question 1

Nonsense mutations occur when is introduced into the coding sequence of a gene.&#10;A)a start codon&#10;B)a stop codon&#10;C)a deletion&#10;D)an insertion

Accepted Answer

Nonsense mutations occur when a premature stop codon is introduced into the coding sequence of a gene, leading to a truncated and usually non-functional protein. A start codon is necessary for translation to begin but its introduction would not necessarily result in a nonsense mutation. Deletions and insertions can also lead to frameshift mutations, which can alter the reading frame and also result in a non-functional protein, but these are not specific to introducing premature stop codons.

Question 2

In some repair mechanisms,the parental DNA strand is used as a guide for repairing mistakes made in the newly synthesized DNA strand.The cell is able to distinguish the parental strand from the new strand because immediately following replication,the DNA is .

A)fully methylated
B)still single-stranded
C)hemi-methylated
D)non-methylated

C

Accepted Answer

Immediately following replication, the DNA is hemi-methylated, meaning that only one strand is methylated while the other is non-methylated. This allows the cell to distinguish between the parental strand and the newly synthesized strand, as the parental strand will be fully methylated while the new strand will only be hemi-methylated.

Question 3

A mutation that changes the orientation of a segment of DNA is called aan).&#10;A)inversion&#10;B)tranversion&#10;C)reversion&#10;D)frameshift

Accepted Answer

An inversion mutation changes the orientation of a segment of DNA by reversing it, resulting in the genes within the segment being flipped in order. Tranversion refers to a nucleotide mutation where a purine is replaced by a pyrimidine or vice versa. Reversion refers to a mutation that reverses a previous mutation, restoring the original DNA sequence. Frameshift mutations involve insertions or deletions of nucleotides that shift the reading frame of the gene, resulting in a different amino acid sequence.

Question 4

DNA polymerases often proofread their recently inserted nucleotides.

Accepted Answer

DNA polymerases have a proofreading function that allows them to identify and correct errors in the recently inserted nucleotides during DNA replication. This helps to maintain the accuracy of DNA replication and prevent mutations.

Question 5

A mutation has no effect on phenotype.&#10;A)frameshift&#10;B)deletion&#10;C)silent&#10;D)nonsense

Accepted Answer

A silent mutation is a type of point mutation that does not change the amino acid sequence of a protein because it codes for the same amino acid. This means that there is no effect on the phenotype, as the resulting protein is the same as the original version. Frameshift, deletion, and nonsense mutations all result in changes to the amino acid sequence and therefore can have an effect on the phenotype.

Question 6

Spontaneous mutations occur .&#10;A)from errors in replication&#10;B)when organisms grow at high temperatures&#10;C)in the presence of mutagens&#10;D)from ultraviolet radiation

Accepted Answer

Spontaneous mutations arise from errors in DNA replication, not necessarily due to external factors or environmental conditions.

Question 7

Which of the following is notorious for causing covalent bonding of adjacent thymine residues in DNA?&#10;A)X-rays&#10;B)infrared radiation&#10;C)nucleotide analogs&#10;D)ultraviolet radiation

Accepted Answer

Ultraviolet radiation is notorious for causing covalent bonding of adjacent thymine residues in DNA, resulting in the formation of a thymine dimer. This can lead to DNA mutations and potentially cancer.

Question 8

Mutations occur more frequently in hotspots.

Accepted Answer

Mutations are more likely to occur in certain regions of the genome, called hotspots. These regions may have higher rates of DNA damage or be more prone to replication errors, making mutations more likely to occur.

Question 9

Terotogenic agents .&#10;A)generate reversions&#10;B)always causes mutations&#10;C)are always carcinogenic&#10;D)have known effects on developing embryos

Accepted Answer

Teratogenic agents have known effects on developing embryos. These effects can range from structural abnormalities to functional deficits in the developing organism. It is important to avoid exposure to teratogenic agents during pregnancy to minimize the risk of birth defects. Teratogenic agents do not necessarily generate reversions, cause mutations, or always be carcinogenic.

Question 10

A mutation changes the coding sequence of the gene by inserting or deleting a single base pair.&#10;A)nonsense&#10;B)silent&#10;C)frameshift&#10;D)reversion

Accepted Answer

Frameshift mutations result from the insertion or deletion of one or more base pairs, which alters the reading frame of the gene and changes the amino acid sequence of the resulting protein. Nonsense mutations create a premature stop codon, leading to a truncated protein that is often nonfunctional. Silent mutations, on the other hand, do not change the amino acid sequence because they occur in a region of the gene that does not code for a protein. Reversion mutations return the gene to its original sequence, which is not the case with frameshift mutations.

Question 11

When second site mutations change the mutant phenotype back to the wild type,this is called .&#10;A)inversion&#10;B)reversion&#10;C)nonsense mutation&#10;D)transversion

Accepted Answer

The answer of When second site mutations change the mutant...

Deck 23: Mutations and Repair