Question 1

Which of the following best describes the antiparallel structure of DNA as discovered by Watson and Crick?

Accepted Answer

One DNA strand runs 5’ to 3’ and the other runs 3’ to 5’.

Question 2

A scientist isolates a segment of DNA and finds that it contains 30% adenine. According to Chargaff’s rule, what percentage of the DNA is cytosine?

Accepted Answer

$$20\%$$

Question 3

Which of the following best explains why histones are important for DNA packaging in eukaryotic cells?

Accepted Answer

Histones allow DNA to coil tightly, forming chromatin.

Question 4

Which of the following statements about euchromatin and heterochromatin is correct?

Accepted Answer

Euchromatin is less condensed and more transcriptionally active than heterochromatin.

Question 5

During transcription in eukaryotes, which sequence signals the start of a gene and is recognized by transcription factors?

Accepted Answer

Promoter

Question 6

A mutation changes a DNA codon from $$	ext{GAA} to$$ $$	ext{GAG}$$, but both codons code for glutamic acid. What type of mutation is this?

Accepted Answer

Silent mutation

Question 7

Which of the following best describes the function of aminoacyl-tRNA synthetases during translation?

Accepted Answer

They attach amino acids to their corresponding tRNAs.

Question 8

A patient is diagnosed with a genetic disorder caused by a single nucleotide insertion in a coding region. Which of the following best describes the likely effect on the resulting protein?

Accepted Answer

A frameshift mutation will alter the reading frame, potentially changing every amino acid downstream.

Question 9

Which of the following is NOT a step in eukaryotic mRNA processing?

Accepted Answer

Removal of exons

Question 10

Which site on the ribosome holds the tRNA carrying the next amino acid to be added to the polypeptide chain?

Accepted Answer

A-site

Question 11

A researcher observes that a certain gene is not being expressed in a region of the chromosome that is highly condensed. Which form of chromatin is most likely present?

Accepted Answer

Heterochromatin

Question 12

Which of the following best explains the 'wobble' hypothesis in translation?

Accepted Answer

The third base of the codon can pair with multiple bases in the anticodon.

Question 13

Which of the following mutations would most likely result in a truncated (shortened) protein?

Accepted Answer

Nonsense mutation

Question 14

Which of the following is true regarding the sugar-phosphate backbone of DNA?

Accepted Answer

It is formed by covalent bonds between the sugar of one nucleotide and the phosphate of the next.

Question 15

Which enzyme is responsible for synthesizing RNA during transcription?

Accepted Answer

RNA polymerase

Question 16

A DNA template strand has the sequence $$5'	ext{-AGTCCG-}3'. $$What is the sequence of the mRNA transcribed from this template?

Accepted Answer

$$5'	ext{-CGGACU-}3'$$

Question 17

Which of the following best describes a codon?

Accepted Answer

A sequence of three nucleotides in mRNA that codes for a specific amino acid.

Question 18

Which of the following is a function of the 5’ cap added to eukaryotic mRNA?

Accepted Answer

It helps protect mRNA from degradation and assists in ribosome binding.

Question 19

A mutagen is best described as:

Accepted Answer

A chemical or physical agent that increases the rate of mutation.

Question 20

Which of the following best explains why a frameshift mutation is often more damaging than a point mutation?

Accepted Answer

Frameshift mutations can alter every amino acid downstream of the mutation, while point mutations usually affect only one codon.

Study Guide: Molecular Basis of Inheritance & Gene Expression (Chapters 13 & 14)

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