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 mutant Neurospora strain can grow on minimal medium supplemented with citrulline but not with ornithine, which enzyme is most likely defective 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, which of the following modifications occurs to pre-mRNA before it becomes mature mRNA?

Accepted Answer

Addition of a 5' cap and a poly-A tail

Question 4

A mutation changes the DNA sequence from 5'-GAA-3' to 5'-GAG-3'. Both codons code for glutamic acid. What type of mutation is this?

Accepted Answer

Silent mutation

Question 5

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

Accepted Answer

The code is redundant but not ambiguous

Question 6

During translation, which site on the ribosome holds the tRNA carrying the next amino acid to be added to the chain?

Accepted Answer

A site

Question 7

Which of the following is a function of the 5' cap and poly-A tail added to eukaryotic mRNA?

Accepted Answer

They help export mRNA from the nucleus

Question 8

A point mutation results in a codon change from UAU (tyrosine) to UAA (stop codon). What is the consequence of this mutation?

Accepted Answer

Nonsense mutation

Question 9

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

Accepted Answer

Aminoacyl-tRNA synthetase

Question 10

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

Accepted Answer

Transcription and translation both occur in the cytoplasm

Question 11

A mutation causes the insertion of a single nucleotide into the coding region of a gene. What is the most likely result?

Accepted Answer

Frameshift mutation

Question 12

Which of the following best explains why alternative RNA splicing increases protein diversity in eukaryotes?

Accepted Answer

It allows different combinations of exons to be joined

Question 13

Which of the following is true about ribozymes?

Accepted Answer

They are RNA molecules with catalytic activity

Question 14

A patient is diagnosed with sickle-cell anemia, which is caused by a single nucleotide substitution in the β-globin gene. What type of mutation is responsible for this disease?

Accepted Answer

Missense mutation

Question 15

Which of the following statements about codons is correct?

Accepted Answer

Codons must be read in the correct reading frame

Question 16

During the elongation phase of translation, what is the correct order of events?

Accepted Answer

Codon recognition, peptide bond formation, translocation

Question 17

Which of the following best describes the role of the spliceosome?

Accepted Answer

It removes introns and joins exons in pre-mRNA

Question 18

A gene contains the following sequence on the template strand: 3'-TAC-5'. What is the corresponding mRNA codon produced during transcription?

Accepted Answer

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

Question 19

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

Accepted Answer

A codon is changed to a stop codon, terminating translation

Question 20

Which of the following best explains why ribosomes can be found both free in the cytosol and bound to the endoplasmic reticulum in eukaryotic cells?

Accepted Answer

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

Chapter 17 Biology

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