Genetics Final

Shown below is a list of statements (a-j) and types of mutations (i-v). On the blank line following each mutation, write the letter(s) of all statements that apply to that type of mutation. Each statement may be used more than once and each type of mutation may have more than one correct answer. a) A mutation that changes UUA to UUG b) A mutation that gives methionine instead of leucine c) A mutation created by the addition of an extra nucleotide to a coding region d) An amino acid is replaced by a chemically similar amino acid due to this mutation e) A mutation that changes CCU to ACU f) Deleting a nucleotide in a coding region gives this type of mutation g) A mutation that does not alter the peptide sequence h) A mutation changing UAU to UAG i) A premature termination codon is responsible for this mutation j) An amino acid is replaced by a chemically different amino acid due to this mutation (i) Missense mutation (ii) Silent mutation (iii) Frameshift mutation (iv) Nonsense mutation (v) Synonymous mutation

(i) Missense mutation b, d, e, j (could also list c, f) (ii) Silent mutation a, g (iii) Frameshift mutation c, f (iv) Nonsense mutation h, i (could also list c, f) (v) Synonymous mutation a, g

What is a nonsense mutation?

A point mutation that converts an amino acid codon into a stop codon.

Human albinism is an autosomal recessive trait. Suppose that there is a village in Thailand where 1/10 of the population is albino. If the size of the village is 900 individuals and the population is in Hardy-Weinberg equilibrium, how many individuals are expected to be heterozygous? A. 389 B. 90 C. 421 D. 810 E. 900

A. 389

In base-excision repair, which enzyme is used to cleave base-sugar bonds, thus creating apurinic or apyrimidinic sites? A. DNA glycosylase B. DNA helicase C. UvrA D. AP endonuclease E. Restriction enzymes

A. DNA glycosylase

A mutation that changes the codon ACC to the codon ACG in a mammalian cell line is called: A. Synonymous mutation B. Nonsense mutation C. Frameshift mutation D. Missense mutation E. Antisense mutation

A. Synonymous mutation

Suppose a GTP analog is found that strongly inhibits Ras activity when bound to the mutant Ras protein (remember that Ras is an oncogene). Would this compound be an effective treatment for cancer? A. True B. False

A. True

For many generations, the following genotypic frequencies were observed in a large population of dinosaurs: 4 percent AA, 32 percent Aa, and 64 percent aa. The climate changed abruptly and resulted in the death of all homozygous recessive dinosaurs. In the next generation, the recessive homozygotes died shortly after birth. What percentage of these newborn dinosaurs died? A. 4% B. 19.7% C. 36.8% D. 8.5% E. 44%

B. 19.7%

A nonsense mutation converts: A. An amino acid to another amino acid as a result of a nucleotide substitution. B. A triplet codon coding for an amino acid to a stop codon. C. A stop codon to a triplet codon coding for an amino acid. D. A non-coding stretch of DNA to an open reading frame.

B. A triplet codon coding for an amino acid to a stop codon.

After mutagen treatment, a molecule of 2-aminopurine (an adenine analogue) incorporates into DNA and initially pairs with thymine. During replication, the 2-AP protonates. The mutational event caused by this will be: A. GC to AT B. AT to GC C. AT to CG D. GC to CG E. AT to TA

B. AT to GC

Predictable changes in allele frequencies occur in small populations as a result of genetic drift. A. True. B. False

B. False

Which of the following describes a non-conservative missense mutation? A. An extra nucleotide is incorporated into a gene. B. Mutant triplet codon codes for a different amino acid with a chemical structure that is very different than the original amino acid. C. Mutant triplet codon codes for the same amino acid as the original codon. D. Mutant triplet codon changes an amino acid to a stop codon. E. Mutant triplet codon codes for a different amino acid with a chemical structure that is similar to the original amino acid.

B. Mutant triplet codon codes for a different amino acid with a chemical structure that is very different than the original amino acid.

A guanine to thymine OR thymine to guanine mutation is called a: A. Transcription mutation B. Transversion mutation C. Conditional mutation D. Transition mutation E. Translation mutation

B. Transversion mutation

Which of the following mutations will result in cancer? A. A dominant mutation that results in reduced expression of an oncogene. B. A dominant mutation that results in overexpression of a tumor suppressor gene. C. A homozygous recessive mutation in a tumor suppressor gene that results in a non-functional protein. D. A homozygous recessive mutation in an oncogene that results in a non-functional protein. E. None of the above.

C. A homozygous recessive mutation in a tumor suppressor gene that results in a non-functional protein.

Inbreeding leads to a decreased level of: A. Homozygosity B. Migration C. Heterozygosity D. Assortative mating

C. Heterozygosity

The class of genes that block cell division (or stimulate apoptosis) in cancerous cells are called: A. DNA repair genes B. Cytoskeletal genes C. Tumor suppressor genes D. House-keeping genes E. Oncogenes

C. Tumor suppressor genes

The Basque people of the Pyrenees Mountains in Spain and France are linguistically and culturally distinct from other Europeans. This group is thought to be descended from pre-Neolithic people and has not intermarried much with other Europeans. Hence, this group also shows differences in allele frequencies from other Europeans. For example, the incidence of a blood disease caused by an autosomal recessive mutation is 1 case in 1 million people in Europeans. In contrast, 200 cases occur per 1 million people in the Basque. What is the frequency of the disease allele in the Basque if the gene is in Hardy-Weinberg equilibrium? A. 200 B. 0.0002 C. 0.001 D. 0.01414 E. 0.000001

D. 0.01414

In a human population, the genotype frequencies at one locus are 0.5 AA, 0.4 Aa, and 0.1 aa. The frequency of the A allele is: A. 0.50 B. 0.32 C. 0.90 D. 0.20 E. 0.70

E. 0.70

A small (five base pair) insertion in the middle of the coding region of a gene will cause a: A. Missense mutation B. Nonsense mutation C. Synonymous mutation D. Silent mutation E. Frameshift mutation

E. Frameshift mutation

A population is reproductively isolated. Which of the following is primarily responsible for the introduction of new alleles into the population? A. Independent assortment during meiosis. B. Somatic cell mutations. C. Inbreeding. D. Assortative mating. E. Germ line mutations.

E. Germ line mutations.

Different rates of survival/reproduction for individuals with different phenotypes is: A. Genetic drift B. Mutation C. Inbreeding D. Migration E. Natural selection

E. Natural selection

Alternative forms of a gene regulate fruit shape in tomatoes. The dominant O allele causes development of round fruit. The recessive o allele results in oblong fruit (i.e., Roma tomatoes). The following genotype frequencies were found in a population of tomatoes growing in the wild. OO 270 Oo 460 oo 220 Calculate p = the frequency of the O allele and q = the frequency of the o allele in this population. A. p = 0.768, q = 0.232 B. p = 0.484, q = 0.516 C. p = 0.284, q = 0.716 D. p = 0.452, q = 0.548 E. p = 0.526, q = 0.473

E. p = 0.526, q = 0.473

What effect do nonsense mutations have on the length of mRNA?

No effect.

What effect do nonsense mutations have on the length and function of a protein?

Nonsense mutations cause premature termination of translation. Thus, the protein will be shorter and probably non-functional.