Question 1

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

Accepted Answer

DNA — RNA — Protein

Question 2

In eukaryotic cells, what is the primary function of the 5' cap and poly-A tail added to pre-mRNA during RNA processing?

Accepted Answer

They facilitate export of mRNA from the nucleus, protect mRNA from degradation, and assist ribosome binding.

Question 3

A mutation changes a codon from $$UAC to$$ $$UAA in an $$mRNA sequence. What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; introduces a premature stop codon

Question 4

Which enzyme is responsible for synthesizing RNA from a DNA template during transcription?

Accepted Answer

RNA polymerase

Question 5

What is the consequence of a frameshift mutation caused by the insertion of a single nucleotide within the coding region of a gene?

Accepted Answer

The reading frame of the mRNA is altered, potentially changing every amino acid downstream.

Question 6

During translation, which site on the ribosome holds the tRNA carrying the growing polypeptide chain?

Accepted Answer

P site

Question 7

Which of the following statements about the genetic code is TRUE?

Accepted Answer

It is universal; most organisms use the same codon assignments.

Question 8

A scientist transplants a gene from a jellyfish into a bacterium, and the bacterium produces a fluorescent protein. What property of the genetic code does this experiment demonstrate?

Accepted Answer

The genetic code is universal.

Question 9

Which process removes introns from pre-mRNA and joins exons together in eukaryotic cells?

Accepted Answer

RNA splicing

Question 10

What is the role of aminoacyl-tRNA synthetase in translation?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA.

Question 11

A patient has a mutation in the gene encoding the enzyme required for pigment synthesis, resulting in no pigment production. Which best explains the link between genotype and phenotype in this scenario?

Accepted Answer

The mutation changes the DNA sequence, which alters the mRNA and results in a nonfunctional protein, leading to the phenotype.

Question 12

Which of the following is a post-translational modification that can affect protein function?

Accepted Answer

Glycosylation (addition of sugars)

Question 13

In prokaryotes, why can translation begin before transcription is complete?

Accepted Answer

Transcription and translation both occur in the cytoplasm, allowing coupling of the processes.

Question 14

Which of the following mutations is most likely to result in a nonfunctional protein?

Accepted Answer

Nonsense mutation

Question 15

Given the DNA template strand sequence $$3'\ AGT\ TCA\ GGC\ 5'$$, what is the corresponding mRNA sequence?

Accepted Answer

$$5'\ UCA\ AGU\ CCG\ 3'$$

Question 16

Which of the following best describes alternative RNA splicing?

Accepted Answer

The process by which different exons are joined together to produce multiple polypeptides from a single gene.

Question 17

A chemical mutagen causes a substitution of a nucleotide pair in DNA. Which of the following is a possible outcome?

Accepted Answer

A silent mutation, missense mutation, or nonsense mutation, depending on the codon affected.

Question 18

During translation, what is the function of the signal-recognition particle (SRP)?

Accepted Answer

It binds to the signal peptide and directs the ribosome to the endoplasmic reticulum.

Question 19

Which of the following best explains why the genetic code is described as 'redundant but not ambiguous'?

Accepted Answer

More than one codon can specify the same amino acid, but each codon specifies only one amino acid.

Question 20

Which of the following is a real-life example of a point mutation causing a dramatic change in phenotype?

Accepted Answer

A single nucleotide change in the hemoglobin gene causing sickle-cell anemia.

Ch. 17 Gene Expression: From Gene to Protein (Campbell Biology, Chapter 17)

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