Genetics - chapter 19 Questions With Complete Solutions
Are most cancers germ-line or somatic? Correct Answers
Mostly somatic.
Describe homologous recombination repair (HRR). Correct
Answers Uses an intact homologous DNA sequence as a
template for accurate repair.
Describe non-homologous end joining (NHEJ). Correct
Answers Directly ligates DNA ends with limited processing,
often causing small insertions/deletions.
Give an example of an intercalating agent. Correct Answers
Ethidium bromide, commonly used as a DNA stain.
How can mutations outside coding regions affect expression?
Correct Answers They can alter transcription, translation, or
mRNA stability.
How does ionizing radiation (X-rays, γ-rays) damage DNA?
Correct Answers Generates free radicals, causing strand breaks
and chromosomal rearrangements.
How does MutH distinguish new DNA? Correct Answers It
recognizes hemi-methylated GATC sites; only the parental
strand is methylated.
How does UV light damage DNA? Correct Answers Causes
pyrimidine dimers (T-T or C-C), distorting the helix.
, Is NHEJ error-prone? Correct Answers Yes, it can delete or
insert bases during rejoining.
What are alkylating agents? Correct Answers Chemicals (e.g.,
EMS) that add methyl or ethyl groups to DNA bases, causing
G:C → A:T transitions.
What are base analogues? Correct Answers Molecules
resembling bases that mispair after incorporation (e.g., 5-
bromouracil mispairs with G).
What are base modifiers? Correct Answers Chemicals (e.g.,
nitrous acid) that deaminate or alkylate bases, altering pairing.
What are chemical mutagens? Correct Answers Chemicals that
increase mutation rates by modifying bases or interfering with
replication.
What are common causes of mutation? Correct Answers
Spontaneous chemical changes, reactive oxygen species,
radiation, and mutagen exposure.
What are double-strand breaks (DSBs)? Correct Answers
Breaks in both DNA strands caused by ionizing radiation,
mutagens, or ROS.
What are intercalating agents? Correct Answers Flat molecules
that insert between bases, distorting DNA and causing insertions
or deletions.
Are most cancers germ-line or somatic? Correct Answers
Mostly somatic.
Describe homologous recombination repair (HRR). Correct
Answers Uses an intact homologous DNA sequence as a
template for accurate repair.
Describe non-homologous end joining (NHEJ). Correct
Answers Directly ligates DNA ends with limited processing,
often causing small insertions/deletions.
Give an example of an intercalating agent. Correct Answers
Ethidium bromide, commonly used as a DNA stain.
How can mutations outside coding regions affect expression?
Correct Answers They can alter transcription, translation, or
mRNA stability.
How does ionizing radiation (X-rays, γ-rays) damage DNA?
Correct Answers Generates free radicals, causing strand breaks
and chromosomal rearrangements.
How does MutH distinguish new DNA? Correct Answers It
recognizes hemi-methylated GATC sites; only the parental
strand is methylated.
How does UV light damage DNA? Correct Answers Causes
pyrimidine dimers (T-T or C-C), distorting the helix.
, Is NHEJ error-prone? Correct Answers Yes, it can delete or
insert bases during rejoining.
What are alkylating agents? Correct Answers Chemicals (e.g.,
EMS) that add methyl or ethyl groups to DNA bases, causing
G:C → A:T transitions.
What are base analogues? Correct Answers Molecules
resembling bases that mispair after incorporation (e.g., 5-
bromouracil mispairs with G).
What are base modifiers? Correct Answers Chemicals (e.g.,
nitrous acid) that deaminate or alkylate bases, altering pairing.
What are chemical mutagens? Correct Answers Chemicals that
increase mutation rates by modifying bases or interfering with
replication.
What are common causes of mutation? Correct Answers
Spontaneous chemical changes, reactive oxygen species,
radiation, and mutagen exposure.
What are double-strand breaks (DSBs)? Correct Answers
Breaks in both DNA strands caused by ionizing radiation,
mutagens, or ROS.
What are intercalating agents? Correct Answers Flat molecules
that insert between bases, distorting DNA and causing insertions
or deletions.
