Q: A patient’s BRCA1 gene is sequenced and three mutations are found: C93T, C121A, and T2161G. The T2161G mutation causes a P721V amino acid change and is found in 3% of individuals in a non-filtered database. What is the probability that a randomly selected individual is heterozygous for T2161G, assuming Hardy-Weinberg equilibrium?

$$2pq$$, where $$p = 0.97$$ and $$q = 0.03$$; $$2 \times 0.97 \times 0.03 = 0.0582 or 5.82$$%.

Question 1

Which of the following best describes the role of mutations in the development of cancer?

Accepted Answer

Mutation rates are increased in somatic cells, contributing to cancer.

Question 2

A proto-oncogene becomes an oncogene through which type of genetic alteration?

Accepted Answer

Gain-of-function mutation in one allele.

Question 3

Tumor suppressor genes typically require which genetic event to contribute to cancer development?

Accepted Answer

Loss-of-function mutation in both alleles.

Question 4

Which of the following is NOT a common feature of human cancer cells?

Accepted Answer

Lower DNA mutation rate.

Question 5

Why are most cancers not considered inherited, even though cancer risk can be inherited?

Accepted Answer

'Cancer' mutations are not inherited, but the possibility of being mutated is.

Question 6

A woman is heterozygous for a loss-of-function BRCA1 mutation. What is her approximate risk of developing breast cancer compared to women without the mutation?

Accepted Answer

Her risk is about 72%.

Question 7

If a direct-to-consumer genetic test for BRCA1 mutations is negative, what is the most accurate advice to give a patient?

Accepted Answer

This doesn't tell you about the function of the BRCA1 gene.

Question 8

Which of the following best explains why only one mutated allele of a proto-oncogene can trigger uncontrolled cell growth?

Accepted Answer

Oncogenes confer a dominant cancer phenotype.

Question 9

Loss-of-heterozygosity (LOH) is most relevant to which type of cancer-related gene?

Accepted Answer

Tumor suppressor genes.

Question 10

Which pathway is most directly associated with the progression from normal colonic epithelium to carcinoma in colon cancer?

Accepted Answer

APC, K-ras, and cell cycle/apoptosis genes.

Question 11

A patient’s BRCA1 gene is sequenced and three mutations are found: C93T, C121A, and T2161G. The T2161G mutation causes a P721V amino acid change and is found in 3% of individuals in a non-filtered database. What is the probability that a randomly selected individual is heterozygous for T2161G, assuming Hardy-Weinberg equilibrium?

Accepted Answer

$$2pq$$, where $$p = 0.97$$ and $$q = 0.03$$; $$2 	imes 0.97 	imes 0.03 = 0.0582 or 5.82$$%.

Question 12

Which experiment would best test the pathogenicity of a newly discovered BRCA1 mutation found in humans?

Accepted Answer

Introduce the mutation into a mouse model using CRISPR and observe cancer incidence.

Question 13

Transposons were discovered by Barbara McClintock using which combination of scientific approaches?

Accepted Answer

Genetics and cytology.

Question 14

Which of the following statements about transposons is TRUE?

Accepted Answer

Transposase recognizes a short motif and can excise and reinsert DNA.

Question 15

In the maize color genetics experiment, what is the expected outcome of a cross between a female with genotype $$c\ bz\ -$$ and a male with genotype $$C'\ BZ\ Ds$$?

Accepted Answer

No color.

Question 16

What is the main reason why most transposons in the human genome are considered 'silent'?

Accepted Answer

They do not encode transposase or are epigenetically silenced.

Question 17

Which of the following best describes the flow of genetic information as proposed by Crick, and how transposons challenge this model?

Accepted Answer

Crick's model: $$DNA \rightarrow RNA \rightarrow Protein$$; transposons: $$DNA \rightarrow DNA.$$

Question 18

Which of the following is a real-world application of double-stranded RNA interference as described in Caenorhabditis elegans?

Accepted Answer

Targeted gene silencing for functional genomics studies.

Genetic Mechanisms of Cancer and Mobile DNA Elements - Nov 17

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