Question 1

Which of the following best describes the structure of DNA as shown in the first image?

Accepted Answer

A double helix composed of two antiparallel strands held together by hydrogen bonds between complementary bases.

Question 2

Which experimental evidence most strongly supports DNA as the genetic material in cells?

Accepted Answer

The transformation of non-virulent bacteria into virulent forms by purified DNA, as shown in the Avery-MacLeod-McCarty experiment.

Question 3

During DNA replication, which enzyme is responsible for synthesizing the new DNA strand by adding nucleotides to the 3' end?

Accepted Answer

DNA polymerase

Question 4

Refer to the schematic model of the ribosome (third image). What is the correct sequence of tRNA binding sites through which a tRNA moves during elongation?

Accepted Answer

A site → P site → E site

Question 5

Which of the following antibiotics specifically targets bacterial ribosomes without affecting eukaryotic ribosomes, and why is this medically important?

Accepted Answer

Tetracycline, because bacterial ribosomes are structurally different from eukaryotic ribosomes.

Question 6

Which of the following best explains why there are only 45 tRNAs for 61 mRNA codons?

Accepted Answer

The rules for base pairing between the third base of a codon and tRNA are flexible (wobble hypothesis).

Question 7

A particular triplet of bases in the template strand of DNA is 3’ TTG 5’. What is the corresponding codon for the mRNA transcribed?

Accepted Answer

5’ AAC 3’

Question 8

Which of the following statements about codons is correct?

Accepted Answer

It can be either in DNA or in RNA.

Question 9

During translation, the ____ site within the ribosome holds the growing amino acid chain while the ____ site holds the next amino acid to be added to the chain.

Accepted Answer

P, A

Question 10

Which of the following events occurs during the termination phase of translation?

Accepted Answer

A release factor binds to the stop codon in the A site, causing hydrolysis of the bond between the polypeptide and tRNA.

Question 11

Which of the following best describes a polyribosome (polysome)?

Accepted Answer

Multiple ribosomes simultaneously translating a single mRNA molecule.

Question 12

In bacteria, transcription and translation can be coupled. What is the main reason this is not possible in eukaryotes?

Accepted Answer

Eukaryotes have a nucleus that separates transcription from translation.

Question 13

Which of the following is a direct result of a mutation in the DNA sequence coding for a protein?

Accepted Answer

A change in the amino acid sequence of the protein.

Question 14

Which of the following steps in translation requires energy in the form of GTP?

Accepted Answer

Translocation of the ribosome along the mRNA.

Question 15

Which of the following best describes the role of rRNA in the ribosome?

Accepted Answer

It catalyzes the formation of peptide bonds between amino acids.

Question 16

A mutation changes the DNA sequence from 5’ ATG 3’ to 5’ ATA 3’. What is the most likely effect on the protein product?

Accepted Answer

The amino acid methionine (Met) will be replaced by isoleucine (Ile) at the corresponding position.

Question 17

Which of the following is true regarding the start and stop signals for transcription and translation?

Accepted Answer

Transcription start and stop sites are found before and after the UTRs, while translation start and stop sites indicate where the amino acid sequence begins and ends.

Question 18

Which of the following best explains why free ribosomes and bound ribosomes synthesize different types of proteins?

Accepted Answer

Free ribosomes synthesize cytosolic proteins, while bound ribosomes synthesize proteins for the endomembrane system or secretion.

Question 19

Which of the following is the correct sequence of events during the elongation cycle of translation?

Accepted Answer

Codon recognition, peptide bond formation, translocation

Translation and Ribosome Function: Structure, Mechanism, and Regulation

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