Q: During DNA replication, which enzyme is primarily responsible for synthesizing the leading strand in E. coli, and what is its directionality?

DNA polymerase III; synthesizes in the $$5' \to 3'$$ direction

Q: A gene has the following coding (non-template) strand: $$5'\text{-}ATG\,GCC\,TAA\,GCT\,TGA\text{-}3'. $$What is the mRNA sequence transcribed from this gene?

$$5'\text{-}AUG\,GCC\,UAA\,GCU\,UGA\text{-}3'$$

Q: Which of the following is a consensus sequence found in prokaryotic promoters and is critical for transcription initiation?

The $$-10 ($$Pribnow) box: $$5'\text{-}TATAAT\text{-}3'$$

Question 1

Which experimental result from the Meselson-Stahl experiment provided the strongest evidence for the semiconservative model of DNA replication?

Accepted Answer

After one generation in $$^{14}\mathrm{N}$$, DNA showed a single intermediate density band.

Question 2

During DNA replication, which enzyme is primarily responsible for synthesizing the leading strand in E. coli, and what is its directionality?

Accepted Answer

DNA polymerase III; synthesizes in the $$5' 	o 3'$$ direction

Question 3

A mutation causes the loss of telomerase activity in a eukaryotic cell. What is the most likely consequence after several rounds of cell division?

Accepted Answer

Progressive shortening of chromosome ends, leading to loss of genetic information

Question 4

Which of the following best describes the difference between continuous and discontinuous DNA synthesis?

Accepted Answer

Continuous synthesis occurs on the leading strand, while discontinuous synthesis (Okazaki fragments) occurs on the lagging strand.

Question 5

Which of the following statements about the directionality of nucleic acids is correct?

Accepted Answer

DNA and RNA polymerases synthesize nucleic acids in the $$5' 	o 3'$$ direction.

Question 6

A gene has the following coding (non-template) strand: $$5'	ext{-}ATG\,GCC\,TAA\,GCT\,TGA	ext{-}3'. $$What is the mRNA sequence transcribed from this gene?

Accepted Answer

$$5'	ext{-}AUG\,GCC\,UAA\,GCU\,UGA	ext{-}3'$$

Question 7

Which of the following best explains why RNA is a necessary intermediate in the central dogma of molecular biology?

Accepted Answer

RNA acts as a messenger, allowing genetic information to be transported from the nucleus to the cytoplasm for protein synthesis.

Question 8

Which of the following is a consensus sequence found in prokaryotic promoters and is critical for transcription initiation?

Accepted Answer

The $$-10 ($$Pribnow) box: $$5'	ext{-}TATAAT	ext{-}3'$$

Question 9

A single nucleotide insertion occurs early in the coding region of a gene. What is the most likely effect on the resulting protein?

Accepted Answer

A frameshift mutation will alter the reading frame, likely resulting in a nonfunctional protein.

Question 10

Which of the following statements about the wobble hypothesis is correct?

Accepted Answer

The third base of a codon can pair with multiple bases in the anticodon, allowing for degeneracy in the genetic code.

Question 11

A mutation changes a codon from $$UAC ($$tyrosine) to $$UAA. $$What is the effect of this mutation?

Accepted Answer

It introduces a premature stop codon, leading to truncated protein synthesis.

Question 12

Which of the following best describes the structure of a tRNA molecule?

Accepted Answer

A cloverleaf structure with an anticodon loop and an amino acid attachment site at the $$3'$$ end.

Question 13

A tRNA with the anticodon $$5'	ext{-}GAA	ext{-}3'$$ will pair with which mRNA codon?

Accepted Answer

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

Question 14

During translation in E. coli, which factor is responsible for recognizing the stop codon and promoting the release of the newly synthesized polypeptide?

Accepted Answer

Release factor (RF)

Question 15

Which of the following best describes the function of aminoacyl-tRNA synthetase?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA, charging the tRNA.

Question 16

Which of the following is a feature of the genetic code?

Accepted Answer

It is degenerate, meaning multiple codons can code for the same amino acid.

Question 17

A patient is found to have a mutation in the promoter region of a gene, reducing the binding affinity of RNA polymerase. What is the most likely effect on gene expression?

Accepted Answer

Transcription of the gene will decrease, leading to lower levels of mRNA and protein.

Question 18

Which of the following correctly matches a posttranscriptional modification with its function in eukaryotes?

Accepted Answer

Addition of a $$5'$$ cap: protects mRNA from degradation and assists in ribosome binding.

Question 19

If a DNA template strand has the sequence $$3'	ext{-}TAC\,GGA\,CTT	ext{-}5'$$, what is the corresponding mRNA sequence?

Accepted Answer

$$5'	ext{-}AUG\,CCU\,GAA	ext{-}3'$$

Step-by-Step Genetics Study Guide: DNA Replication, Transcription, and Translation

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