Question 1

Which of the following best describes the 'genetic approach' to studying a biological process?

Accepted Answer

Looking for mutants in which the process is defective and analyzing their phenotypes.

Question 2

Beadle and Tatum’s experiment with Neurospora crassa led to which major conclusion about gene function?

Accepted Answer

Each gene encodes a specific enzyme that affects a single step in a metabolic pathway.

Question 3

Which of the following is a key advantage of using model organisms such as Saccharomyces cerevisiae in genetic studies?

Accepted Answer

Their genes and cellular processes are often conserved in higher eukaryotes, making findings broadly applicable.

Question 4

In the classic yeast cell cycle mutant screen by Hartwell et al., what was the purpose of using temperature-sensitive mutants?

Accepted Answer

To isolate mutants that could complete the cell cycle only at a permissive temperature but not at a restrictive temperature.

Question 5

Which equation best represents the probability of finding a mutant in a population after exposure to a mutagen, assuming mutation rate $$\mu$$ and population size $$N$$?

Accepted Answer

$$P = 1 - (1 - \mu)^N$$

Question 6

In the ABC model of flower development in Arabidopsis thaliana, which combination of gene activities specifies the identity of petals?

Accepted Answer

Class A and Class B genes together

Question 7

A mutant Arabidopsis flower lacks both stamens and carpels. According to the ABC model, which class of gene is most likely mutated?

Accepted Answer

Class C

Question 8

Why are complementation tests important in genetic screens?

Accepted Answer

They determine whether two mutations are in the same gene or in different genes.

Question 9

Which of the following best explains why findings from yeast cell cycle mutants are relevant to human biology?

Accepted Answer

Yeast and humans share homologous genes that control the cell cycle.

Question 10

A yeast strain with a mutation in the $$cdc28$$ gene arrests in which phase of the cell cycle?

Accepted Answer

G1 phase

Question 11

Which of the following is a real-world application of the genetic approach in medicine?

Accepted Answer

Identifying genes responsible for inherited diseases by screening for mutants with disease phenotypes.

Question 12

In a genetic screen, why is it useful to use haploid organisms like yeast?

Accepted Answer

Mutations are immediately expressed in the phenotype, without being masked by a second allele.

Question 13

Which of the following statements about mutagenesis is correct?

Accepted Answer

Induced mutagenesis involves exposing organisms to chemicals or radiation to increase mutation rates.

Question 14

If a yeast mutant can grow at 23°C but not at 36°C, what type of mutant is it?

Accepted Answer

Temperature-sensitive mutant

Question 15

Which of the following best describes the concept of a 'model organism' in genetics?

Accepted Answer

A species that is easy to manipulate genetically and provides insights applicable to other species.

Question 16

In the lac operon genetic screen, which class of mutants expressed the lac operon genes constitutively, even in the absence of lactose?

Accepted Answer

lacC mutants

Question 17

Which of the following is a direct outcome of performing a complementation test between two mutants?

Accepted Answer

Determining if the mutations are in the same gene or different genes.

Question 18

According to the ABC model, what would be the phenotype of an Arabidopsis flower mutant lacking both class A and class C gene function?

Accepted Answer

All whorls develop as leaves or undifferentiated organs.

Question 19

Which of the following best explains why the ABC model of flower development was considered a breakthrough in plant genetics?

Accepted Answer

It demonstrated that organ identity is determined by the combinatorial expression of transcription factors in specific whorls.

Genetic Analysis of Biological Processes: Model Systems, Mutant Screens, and Developmental Genetics 19

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