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

$$\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$$

Question 1

Beadle and Tatum’s experiments with Neurospora crassa demonstrated that genes specify the production of specific enzymes. If a Class II mutant can grow on minimal medium supplemented with citrulline but not ornithine, which enzyme is most likely nonfunctional in this mutant?

Accepted Answer

Enzyme B (converts ornithine to citrulline)

Question 2

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

Accepted Answer

$$	ext{DNA} ightarrow 	ext{RNA} ightarrow 	ext{Protein}$$

Question 3

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

Accepted Answer

They facilitate export of mRNA, protect it from degradation, and help ribosome binding

Question 4

A mutation changes a codon from $$	ext{UAC} to$$ $$	ext{UAA}. $$What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; introduces a premature stop codon

Question 5

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

Accepted Answer

It is redundant; multiple codons can specify the same amino acid

Question 6

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

Accepted Answer

P site

Question 7

A patient has a genetic disorder caused by a single nucleotide substitution in the coding region of a gene. The resulting protein has a single amino acid change. What type of mutation is this?

Accepted Answer

Missense mutation

Question 8

Which of the following best explains why eukaryotic mRNA must be processed before translation, but prokaryotic mRNA does not?

Accepted Answer

Eukaryotic genes contain introns that must be removed

Question 9

If a DNA template strand has the sequence $$3'	ext{-TACGGTACC-}5'$$, what is the corresponding mRNA sequence produced during transcription?

Accepted Answer

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

Question 10

Which enzyme is responsible for attaching the correct amino acid to its corresponding tRNA?

Accepted Answer

Aminoacyl-tRNA synthetase

Question 11

Alternative RNA splicing allows eukaryotic cells to:

Accepted Answer

Produce multiple proteins from a single gene

Question 12

Which of the following is a direct result of a frameshift mutation?

Accepted Answer

All amino acids downstream of the mutation are altered

Question 13

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

Accepted Answer

There is no nuclear envelope separating the processes

Question 14

A mutation in the promoter region of a gene would most likely affect which stage of gene expression?

Accepted Answer

Transcription initiation

Question 15

Which of the following best describes the role of ribozymes in cells?

Accepted Answer

They are RNA molecules that act as enzymes, such as in RNA splicing

Question 16

A patient’s hemoglobin gene has a point mutation that changes the codon $$	ext{GAG} to$$ $$	ext{GTG} in $$DNA. What is the effect on the protein, and what disease is associated with this mutation?

Accepted Answer

Glutamic acid is replaced by valine; sickle-cell disease

Question 17

Which of the following is NOT a function of the 5′ cap and poly-A tail in eukaryotic mRNA?

Accepted Answer

Coding for amino acids in the protein

Question 18

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

Accepted Answer

RNA splicing

Question 19

A tRNA has the anticodon $$5'	ext{-GAA-}3'. $$Which mRNA codon will it recognize, and which amino acid will it carry?

Accepted Answer

Codon $$5'	ext{-UUC-}3'$$, amino acid Phenylalanine

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