Q: Which equation correctly represents the probability of two independent events both occurring?

$$P(A \text{ and } B) = P(A) \times P(B)$$

Question 1

A couple has one child and plans to have a second. The father is a carrier for Tay-Sachs, and the mother is also a carrier. What is the probability that their second child will have Tay-Sachs disease? Use the following: Tay-Sachs is autosomal recessive. Show your calculation.

Accepted Answer

The probability is $$\frac{1}{4}$$

Question 2

Which of the following best describes the difference between forward genetics and reverse genetics?

Accepted Answer

Forward genetics starts with a phenotype and identifies the gene; reverse genetics starts with a gene and studies its function.

Question 3

CRISPR/Cas9 is a powerful tool in genetics because it allows researchers to:

Accepted Answer

Precisely edit DNA sequences at targeted locations

Question 4

In a forward genetic screen, mutagenesis is used to:

Accepted Answer

Induce random mutations throughout the genome

Question 5

A geneticist uses CRISPR/Cas9 to knock out a gene in human blood stem cells. What type of allele is most likely generated by this approach?

Accepted Answer

Null (loss-of-function) allele

Question 6

Which of the following is a key step in the CRISPR/Cas9 genome editing process?

Accepted Answer

Hybridization of guide RNA to complementary DNA sequence

Question 7

In a genetic screen for recessive alleles in a self-fertilizing organism, why is it important to propagate the F2 generation?

Accepted Answer

To allow homozygous recessive mutants to be observed

Question 8

Which of the following best explains why forward genetics is considered an unbiased approach?

Accepted Answer

It does not require knowledge or hypothesis about which genes might regulate a trait

Question 9

A researcher wants to identify all genes that can confer HIV resistance in human T-cells. Which genetic approach would be most suitable?

Accepted Answer

Combining reverse and forward genetic approaches using CRISPR/Cas9

Question 10

Which of the following is NOT a method for identifying genes involved in a process of interest?

Accepted Answer

Gene therapy

Question 11

A null allele is most useful for geneticists because:

Accepted Answer

It provides a starting point for studying loss-of-function phenotypes

Question 12

Which equation correctly represents the probability of two independent events both occurring?

Accepted Answer

$$P(A 	ext{ and } B) = P(A) 	imes P(B)$$

Question 13

In a genetic screen for dominant alleles, why is it important to screen the F1 generation?

Accepted Answer

Dominant mutations will be expressed in heterozygotes in the F1

Question 14

Which of the following is a real-world application of CRISPR/Cas9 technology?

Accepted Answer

Generating loss-of-function alleles in human blood stem cells

Question 15

A researcher hypothesizes that a gene regulates a trait based on prior knowledge of homologous gene function in other organisms. Which genetic approach is most appropriate?

Accepted Answer

Reverse genetics

Question 16

Which of the following statements about mutagens is correct?

Accepted Answer

Mutagens induce random mutations throughout the genome

Question 17

In a genetic screen for recessive alleles in Drosophila, why is an extra generation required compared to self-fertilizing organisms?

Accepted Answer

Drosophila cannot self-fertilize, so homozygous recessive mutants only appear in the F3

Question 18

Which of the following is NOT a level at which a gene's function may be described?

Accepted Answer

Chromosome number

Question 19

Which repair pathway is used by cells after CRISPR/Cas9-induced double-strand breaks to introduce defined sequence changes?

Accepted Answer

Homology-directed repair (HDR)

Question 20

Which of the following is a limitation of most reverse genetics technologies?

Accepted Answer

They are only available in a limited group of model organisms

Genetic Screens, Alleles, and Gene Function: Study Notes for Genetics

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