Question 1

Which of the following organisms is commonly used as a model for studying developmental genetics and has contributed to our understanding of circadian rhythms and mutant phenotypes?

Accepted Answer

Drosophila melanogaster

Question 2

Ethyl methanesulfonate (EMS) is a chemical mutagen that induces mutations by modifying DNA bases. What specific base change does EMS most commonly cause?

Accepted Answer

G/C to A/T

Question 3

In a forward genetics experiment, you observe a 3:1 ratio of wild type to mutant phenotype in the F2 generation. What does this ratio indicate about the mutation?

Accepted Answer

The mutation is recessive and affects a single nuclear gene.

Question 4

Which of the following best describes the principle of genetic linkage mapping used in positional cloning?

Accepted Answer

Genes close together on the same chromosome are more likely to be inherited together due to low recombination frequency.

Question 5

In the context of linkage mapping, what is the recombination frequency between two loci that are unlinked?

Accepted Answer

$$50\%$$

Question 6

You are analyzing F2 progeny that are homozygous for a recessive mutation. What is the allele frequency of the mutant SNP in this subset?

Accepted Answer

$$100\%$$

Question 7

In a pool of F2 progeny homozygous for a recessive mutation, what is the expected allele frequency of a SNP that is unlinked to the mutation?

Accepted Answer

$$50\%$$

Question 8

Which of the following is a key advantage of using Arabidopsis thaliana as a model organism in genetics research?

Accepted Answer

It produces many seeds and has a short life cycle.

Question 9

In positional cloning by sequencing, what does a SNP allele frequency approaching $$100\% in $$the F2 mutant pool indicate?

Accepted Answer

The SNP is closely linked to the causative mutation.

Question 10

Which repair pathway is most commonly used to generate loss-of-function mutations in genes using CRISPR-Cas9?

Accepted Answer

Non-homologous end joining (NHEJ)

Question 11

A researcher uses CRISPR-Cas9 to knock out two eIF4E genes in cassava. What is the expected outcome regarding resistance to cassava brown streak disease?

Accepted Answer

The double knockout plants show resistance to the virus.

Question 12

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 identifies its phenotype.

Question 13

A mutation caused by EMS results in a missense mutation in a gene. Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes one amino acid to another.

Question 14

In a genetic screen, what is the main difference between a 'selection' and a 'screen'?

Accepted Answer

Selection allows only mutants with the desired phenotype to survive, while screen requires examining all mutants.

Question 15

If a SNP is closely linked to a causative mutation, what is the expected recombination frequency (RF) between them in the F2 mutant pool?

Accepted Answer

$$0\%$$

Question 16

Which of the following is NOT a typical reason for selecting a gene for a reverse genetics experiment?

Accepted Answer

The gene has already been fully characterized in all organisms.

Question 17

A plant mutant is rescued by introducing a wild-type copy of the gene responsible for the phenotype. What does this experiment demonstrate?

Accepted Answer

The wild-type gene can complement the mutant phenotype.

Question 18

Which of the following statements about CRISPR-Cas9 technology in agriculture is correct?

Accepted Answer

CRISPR-Cas9 can edit plant genomes without leaving behind foreign genes used in the process.

Question 19

Which equation best represents the expected ratio of wild type to mutant phenotype in the F2 generation for a recessive mutation in a diploid organism?

Accepted Answer

$$\frac{3}{4}$$ wild type : $$\frac{1}{4}$$ mutant

Question 20

Which of the following is a real-world application of CRISPR-Cas9 gene editing in plants, as discussed in the lecture?

Accepted Answer

Eliminating synthesis of toxic molecules in potatoes.

Lecture 25 (Unit 2) The Awesome Power of Genetics: Forward and Reverse Genetics in Model Organisms

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