BS 161 Chapter 14 Homework

If DNA repair mechanisms were perfect, which of the following would MOST likely result? All of these choices are correct. The rate of evolutionary change would dramatically increase. Humans would live forever. Humans would stop aging, because aging is a collection of DNA mutations. Evolution as we know it would stop because mutations are the only source of new genetic variation.

Evolution as we know it would stop because mutations are the only source of new genetic variation.

In living organisms, on average, about one nucleotide in every _____ is mistakenly substituted for another during each round of DNA replication. 100,000 1 billion 1000 100 10 billion

10 billion

In the standard genetic code (Table 4.1, shown below), how many codons for amino acids allow synonymous mutations in the third position? 29 19 39 49 59

59

A population of mosquitoes is exposed to the pesticide DDT for several generations. At the end of that time, most individuals in the population are resistant to DDT. The MOST likely reason is that: Some individuals in the original population had the mutations that led to resistance. DDT caused the mutations that led to resistance. By chance, new mutations that led to DDT resistance arose after DDT was used. Somatic mutations in the original population were passed on to subsequent generations. Random mutations in each generation made mosquitoes resistant to DDT.

Some individuals in the original population had the mutations that led to resistance.

Why do data on observable mutant phenotypes underestimate the actual frequency of mutation? (Select all that apply.) Most mutations result in death of the individual or an inability to reproduce. Some mutations in protein-coding regions of the genome are synonymous mutations. Many mutations are in noncoding regions of the genome.

Some mutations in protein-coding regions of the genome are synonymous mutations. Many mutations are in noncoding regions of the genome.

A family can share a genetic risk of developing cancer if: All of these choices are correct. the cancer is caused by somatic cell mutations. the cancer is caused by germ-line mutations. a somatic cell mutation in one of the genes implicated in the cancer occurred in an ancestor. a germ-line mutation in one of the genes implicated in the cancer occurred in an ancestor.

a germ-line mutation in one of the genes implicated in the cancer occurred in an ancestor.

Any heritable change in the genetic material is _____. a mutation detrimental to the organism, and potentially, to the species usually the result of a reactive chemical or radiation usually evident in an abnormal number of chromosomes

a mutation

If a cytosine base in DNA is converted into uracil, the site is repaired by: DNA ligase. base excision repair. nucleotide excision repair. mismatch repair.

base excision repair.

Insertions and deletions of single nucleotides: cause frameshift mutations. add or delete amino acids to or from the normal polypeptide. shorten chromosomes. cause missense mutations. cause cancer.

cause frameshift mutations.

A nonsense mutation: shifts the reading frame of a messenger RNA. is usually due to a nucleotide substitution in the third position of a codon. changes a codon for an amino acid into a codon for chain termination. changes the identity of one amino acid in a polypeptide chain.

changes a codon for an amino acid into a codon for chain termination.

A loss-of-function mutation is one in which the function of a gene is completely knocked out or obliterated. Which of the following mutations results in the loss of function of one or more genes? (Select all that apply.) frameshift deletion duplication translocation inversion

deletion frameshift

An agent that increases mutation rate is a _____. carcinogen antigen mutagen teratogen

mutagen

Consider the tryptophan codon 5′-UGG-3′ in the standard genetic code (Table 4.1, shown below). Can a single base change in this codon create a synonymous mutation? Can a single base change in this codon create a nonsense codon? yes; yes no; yes no; no yes; no

no; yes

Point mutations that cause amino acid replacements are called: synonymous (silent) mutation. transition mutation. nonsynonymous (missense) mutation. nonsense mutation. stop mutation.

nonsynonymous (missense) mutation.

The main mutagenic effects of ultraviolet light are to produce chemical cross-links between adjacent thymines in a DNA strand. These could be repaired by: base excision repair. DNA ligase. mismatch repair. nucleotide excision repair.

nucleotide excision repair.

The enzyme _____ repairs 99% of mismatched bases immediately during replication. DNA ligase DNA polymerase None of the answer options is correct. uracyl glycosylase AP endonuclease

DNA polymerase

Mutations will always decrease the activity of a gene. True False

False

Which of the following statements applies to frameshift mutations? They are known risk factors in breast cancer, but not colon cancer. They create a premature stop codon at the site of mutation. They are known risk factors in most forms of cancer, including breast and colon cancer. They cause the insertion or deletion of a single amino acid from the polypeptide chain. They change the amino acid sequence downstream from the mutant site.

They change the amino acid sequence downstream from the mutant site.