Question 1

Which of the following best explains why most scientists initially believed that proteins, rather than DNA, were the genetic material?

Accepted Answer

Proteins have a greater variety of amino acids, allowing for more complex information storage.

Question 2

In Griffith's experiment with Streptococcus pneumoniae, what was the key finding regarding the 'transforming principle'?

Accepted Answer

A non-virulent strain could become virulent when exposed to heat-killed virulent bacteria, suggesting a transferable genetic factor.

Question 3

Avery, MacLeod, and McCarty used enzymes to demonstrate that DNA is the transforming principle. Which enzyme treatment abolished transformation?

Accepted Answer

DNase, which digests DNA

Question 4

In the Hershey and Chase experiment, which isotope was used to label DNA, and what was the significance of its detection in progeny phage?

Accepted Answer

$$^{32}\mathrm{P}$$ was used to label DNA, and its presence in progeny showed DNA is the genetic material.

Question 5

Which of the following correctly describes the three components of a nucleotide and the difference between DNA and RNA nucleotides?

Accepted Answer

A nucleotide consists of a phosphate group, a five-carbon sugar, and a nitrogenous base; DNA contains deoxyribose, while RNA contains ribose.

Question 6

Chargaff's rules state that in double-stranded DNA, the amount of adenine equals thymine and the amount of guanine equals cytosine. Which equation represents this relationship?

Accepted Answer

$$[A] = [T]$$ and $$[G] = [C]$$

Question 7

Why is a G-C base pair more stable than an A-T base pair in DNA?

Accepted Answer

G-C pairs form three hydrogen bonds, while A-T pairs form only two.

Question 8

What does it mean that DNA strands are antiparallel, and why is this important for replication?

Accepted Answer

The two strands run in opposite directions (5' to 3' and 3' to 5'), which is essential for enzymes to synthesize new DNA correctly.

Question 9

In bacterial gene regulation, what is the main difference between inducible and repressible systems?

Accepted Answer

Inducible systems are usually off and can be turned on by an inducer; repressible systems are usually on and can be turned off by a repressor.

Question 10

Which of the following best describes the function of the lac operon in E. coli?

Accepted Answer

It allows the cell to metabolize lactose by producing enzymes encoded by lacZ, lacY, and lacA as a single polycistronic mRNA.

Question 11

What is the difference between cis-acting sites and trans-acting factors in gene regulation, using the lac operon as an example?

Accepted Answer

Cis-acting sites are DNA sequences like the operator; trans-acting factors are proteins like the lac repressor.

Question 12

In the lac operon, what is the effect of an $$O^c ($$operator-constitutive) mutation?

Accepted Answer

The operon is always on, regardless of the presence or absence of lactose.

Question 13

How do partial diploids (merozygotes) help determine whether a mutation acts in cis or in trans?

Accepted Answer

By providing two copies of certain genes or regulatory elements, researchers can see if the mutation affects only the DNA it is on (cis) or can affect other copies (trans).

Question 14

Why does E. coli preferentially use glucose over lactose, and how do cAMP and CAP connect glucose levels to lac operon expression?

Accepted Answer

Low glucose increases cAMP, which binds CAP; the CAP-cAMP complex activates the lac operon, allowing lactose metabolism when glucose is scarce.

Question 15

Given the following conditions, predict the state of the lac operon: Glucose absent, lactose present.

Accepted Answer

The lac operon is fully on, as cAMP-CAP activates transcription and the repressor is inactivated by lactose.

Question 16

Which feature makes eukaryotic gene regulation more complex than bacterial regulation?

Accepted Answer

Eukaryotes have chromatin structure, a nucleus, RNA processing, and mRNA stability mechanisms.

Question 17

How does chromatin remodeling affect gene expression in eukaryotes?

Accepted Answer

Chromatin remodeling makes DNA more accessible to transcription machinery, allowing genes to be transcribed.

Question 18

What is a nucleosome, and what is it composed of?

Accepted Answer

A nucleosome is a unit of chromatin consisting of DNA wrapped around a core of histone proteins.

Question 19

Which equation best represents the relationship between promoter strength and transcription initiation in eukaryotes?

Accepted Answer

$$	ext{Transcription Rate} \propto 	ext{Promoter Strength}$$

Genetics Exam 1 Study Guide: DNA Structure, Bacterial & Eukaryotic Gene Regulation

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