Induced Mutations Practice Problems

Alkaptonuria is a genetic disorder caused by a mutated gene that affects the homogentisic acid oxidase enzyme. The mutant gene has a different BamHI restriction site than the normal gene, resulting in a Ser-to-Thr missense mutation. If a heterozygous mother (Aa) for the mutant gene and a homozygous father (aa) for the mutant gene have children, what is the expected genotypic ratio of the offspring?

Experiments conducted by Charles Yanofsky in the 1950s and 1960s helped characterize the nature of tryptophan synthesis in E. coli. In one of Yanofsky's experiments, he observed that a mutation in the gene caused premature termination of translation due to a stop codon at position 243. Which of the following base-pair substitutions could result in a stop codon at position 243 of tryptophan synthetase?

The amino acid sequence of a fragment of wild-type and mutant polypeptides is given below: 

Wild-type polypeptide:    N . . . Thr–His–Ser–Gly–Leu–Lys–Ala . . . C 

Mutant 1:      N . . . Thr–His–Ser–Val–Leu–Lys–Ala . . . C 

Mutant 2:     N . . . Thr–Gln–Leu–Trp–Ile–Glu–Gly . . .  C

Which of the following statements is correct regarding these sequences?

A wild-type polypeptide has the following sequence:

''Met–Leu–Lys–Thr–Ser–Pro–Gln–His–Arg–Asp–Cys''

Which of the following mutations would result in a truncated polypeptide? 

Escherichia coli bacterial culture undergoes exposure to ultraviolet (UV) radiation. Subsequently, the bacterial cells are cultivated on a complete medium, and 8 individual colonies (numbered 1 to 8) are chosen for further analysis. The complete medium plate is used to create four replica plates, which contain minimal medium or minimal medium added with one antibiotic (replica plates numbered 1 to 4). The results obtained are as follows:

Can you identify the colony or colonies that exhibit resistance to all the tested antibiotics?

A culture of haploid bacteria is exposed to a mutagenic agent and plated on a nutrient-rich medium. Six colonies are selected and transferred to a new plate for further study. The colonies are then replicated onto minimal media with or without specific amino acids. The results are as follows:

Which of the following colonies is most likely to have a mutation in the gene responsible for histidine synthesis? 

The auxotrophic selection method is a genetic research technique used to select and isolate cells with a specific genetic mutation by growing mutant cells on a medium that lacks an essential nutrient that the mutant cells cannot produce. Can you identify the colonies that are his⁻, arg⁻, leu⁻ using this method?

There are many genes associated with Xeroderma pigmentosum (XP) and many of these genes are involved in the DNA-repair process. This disease is characterized by an extreme sensitivity to UV rays. Which of the following genes related to this disease also plays a role in protecting cells from UV-induced damage?

Cyanobacteria were found to have been experiencing a high rate of mutation due to chemical pollution caused by an oil spill. Researchers perform mutagenesis assays using various known mutagens. The results show that the highest rate of reversion occurs when the bacteria are exposed to UV radiation.
Which of the following statements is therefore true about the impact of the oil spill on cyanobacteria?

Radiation can cause mutations in the genome in various ways. Which of the following is considered a chromosomal mutation which may be caused by radiation energy?

Chemical pollutants in the environment can induce different types of gene mutations. If an exposure to a certain chemical triggers the mutation of one nucleotide base, where one nucleotide is replaced by another, this type of mutation is considered a:

UV radiation can create a mutagenic impact on an organism's DNA. The DNA repair mechanism in which the strand segment containing the damaged DNA region is removed and replaced by a new DNA segment is called:

What are the most frequent locations for the formation of UV-induced DNA lesions?

Tobacco-specific nitrosamines and drugs such as streptozotocin can adversely impact the DNA. What type of DNA lesions can result from taking these compounds?

Single-base excision is a type of DNA repair mechanism that involves the removal of a damaged or incorrect base from the DNA molecule. All of the following are examples of single-base repairs, EXCEPT:

Which type of DNA damage can be repaired by the Base Excision Repair (BER) pathway?

Which of the following is a common form of DNA damage induced by exposure to ultraviolet (UV) radiation?

Which of the following is a bypass mechanism that permits the DNA polymerase to duplicate beyond a damaged region in the DNA, perhaps introducing mutations?

Which of the following pathways is responsible for repairing helix-distorting DNA damage?

UV irradiation causes the formation of thymine dimers in bacterial DNA. Photolyase is an enzyme that repairs thymine dimers through a process called:

Aflatoxin causes the formation of adducts with DNA, primarily at guanine bases, forming Aflatoxin-DNA adducts. These adducts can lead to mispairing during DNA replication, resulting in nucleotide substitutions or deletions. These types of mutations are considered:

Radiation can induce a mutation in the DNA sequence in which a single nucleotide is changed. This mutation is called:

A fragment of the polypeptide is sequenced for seven amino acids.
Methionine (Met), Valine (Val), Histidine (His), Leucine (Leu), Threonine (Thr), Proline (Pro), and Glutamic acid (Glu).
What is the mRNA base pair sequence that is complementary to the given polypeptide sequence?

What is the purpose of adding S9 extract in an Ames test?

How does the Ames test evaluate the DNA mutagenicity of a substance in Salmonella bacteria, particularly by using his⁻ strain, when the test compound is a pro-mutagen that requires metabolic activation to become mutagenic?

What is the significance of J. Craig Venter's patent application?

What is the controversy over the patenting of the BRCA1 and BRCA2 genes about?

What options are available to a woman if a BRCA1 gene mutation test results in a positive result?

Ames test is a biological assay that can assess a compound's mutagenic potential. Which of the following organisms are used in this experiment?

The 5-bromouracil is an artificially generated molecule that can be incorporated into the DNA. Since it highly resembles thymine, it can replace the thymine's position in the DNA sequence. Which type of mutagenic agents does 5-bromouracil belong to?

The Chernobyl accident triggered the release of radioactive iodine (I¹³¹) into the environment. This radioactive contaminant caused an increased risk of cancer and other health-related problems among the exposed population. Which of the following is considered one of the main consequences of radioactive iodine exposure?