$$5'\text{-}AUGCCACUCAUU\text{-}3'$$

Question 1

Which experiment provided definitive evidence that DNA, not protein, is the molecule of heredity, and what was the key method used?

Accepted Answer

The Hershey & Chase experiment, which used radioactive labeling of DNA and protein in bacteriophages to track which molecule entered bacterial cells.

Question 2

What are the base pairing rules for DNA, and what type of bond holds the complementary bases together?

Accepted Answer

A pairs with T, G pairs with C; hydrogen bonds hold the bases together.

Question 3

Why is DNA replication described as a semi-conservative process?

Accepted Answer

Each new DNA molecule consists of one old strand and one newly synthesized strand.

Question 4

Which three differences distinguish DNA from RNA?

Accepted Answer

DNA is double-stranded, contains deoxyribose, and uses thymine; RNA is single-stranded, contains ribose, and uses uracil.

Question 5

During transcription, which enzyme synthesizes RNA from a DNA template, and what is the direction of synthesis?

Accepted Answer

RNA polymerase synthesizes RNA in the $$5' \rightarrow 3'$$ direction.

Question 6

Which modifications occur to eukaryotic mRNA after transcription but before translation?

Accepted Answer

Addition of a $$5'$$ cap, addition of a poly-A tail, and removal of introns via splicing.

Question 7

What is the function of tRNA during translation?

Accepted Answer

tRNA transfers specific amino acids from the cytoplasmic pool to the growing polypeptide chain in the ribosome.

Question 8

Which site on the ribosome is responsible for accepting incoming aminoacyl-tRNA during translation?

Accepted Answer

A site (aminoacyl-tRNA binding site)

Question 9

A mutation changes a codon from UAU (tyrosine) to UAA (stop). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 10

If a DNA template strand reads $$3'	ext{-}TACGGTGAGTAA	ext{-}5'$$, what is the corresponding mRNA sequence?

Accepted Answer

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

Question 11

Which of the following best describes a frameshift mutation?

Accepted Answer

A mutation caused by insertion or deletion of nucleotides that alters the reading frame of the genetic message.

Question 12

Which codon serves as the start signal for translation in most organisms?

Accepted Answer

$$AUG$$

Question 13

What is the role of the promoter region in transcription?

Accepted Answer

It is the DNA sequence where RNA polymerase and transcription factors bind to initiate transcription.

Question 14

Which of the following best explains why sickle-cell disease is caused by a missense mutation?

Accepted Answer

A single nucleotide substitution changes a codon, resulting in a different amino acid in the protein's primary structure.

Question 15

Which of the following is NOT a function of the poly-A tail added to eukaryotic mRNA?

Accepted Answer

It catalyzes peptide bond formation during translation.

Question 16

During DNA replication, which enzyme unwinds the DNA double helix?

Accepted Answer

Helicase

Question 17

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

Genetic information flows from DNA to RNA to protein.

Question 18

What is the difference between an intron and an exon in eukaryotic genes?

Accepted Answer

Introns are non-coding regions removed during RNA splicing; exons are coding regions retained in mature mRNA.

Question 19

A mutation changes the DNA sequence but does not alter the amino acid sequence of the protein. What type of mutation is this?

Accepted Answer

Silent mutation

DNA Structure, Replication, Gene Expression, and Mutations: Study Notes

Study Guide - Practice Questions