2.7 DNA replication, transcription, and translation

Question 1

What principle is necessary to preserve the sequence of DNA during replication?

Answer 1

base pairing is complementary

Question 2

Which process is used in polymerase chain reaction (PCR)?

Answer 2

replication

Question 3

what is a codon?

Answer 3

A sequence of nucleotides on mRNA that corresponds to an amino acid

Question 4

What is a polysome?

Answer 4

Several ribosomes using a mRNA molecule to synthesize protein at the same time

Question 5

What enzyme is used in transcription but not in translation?

Answer 5

RNA polymerase

Question 6

A certain gene in a bacterium codes for a polypeptide that is 120 amino acids long. How many nucleotides are needed in the mRNA to code for this polypeptide?

Answer 6

360

Question 7

What does the universal nature of the genetic code allow?

Answer 7

transfer of genes between species

Question 8

Which enzymes are needed to produce recombinant plasmids to be used in gene transfer?

Answer 8

ligase and restriction enzyme

Question 9

Translation occurs in living cells. Explain how translation is carried out, from the initiation stage onwards.

Answer 9

mRNA binds to the small sub-unit of the ribosome;
ribosome slides along mRNA to the start codon;
anticodon of tRNA pairs with codon on mRNA:
(anticodon of) tRNA with methionine pairs with start codon / AUG is the start codon;
second tRNA pairs with next codon;
peptide bond forms between amino acids;
ribosome moves along the mRNA by one codon;
movement in 5′ to 3′ direction;
tRNA that has lost its amino acid detaches;
another tRNA pairs with the next codon/moves into A site;
tRNA activating enzymes;
link amino acids to specific tRNA;
stop codon (eventually) reached;