Chapter 15

Question 1

What are the two main stages of gene expression?

Answer 1

The two main stages of gene expression are transcription and translation.

Question 2

What is transcription?

Answer 2

Transcription is the process by which RNA is synthesized from a DNA template.

Question 3

What enzyme is responsible for transcription?

Answer 3

RNA polymerase is the enzyme responsible for transcription.

Question 4

What is the role of RNA polymerase in transcription?

Answer 4

RNA polymerase pries open the DNA strands and joins RNA nucleotides complementary to the DNA template.

Question 5

What is a promoter in the context of transcription?

Answer 5

A promoter is a specific sequence of nucleotides on the DNA that indicates the beginning of transcription.

Question 6

What is the difference between bacterial and eukaryotic transcription initiation?

Answer 6

In bacteria, RNA polymerase binds directly to the promoter, while in eukaryotes, transcription factors assist RNA polymerase II in recognizing and binding to the promoter.

Question 7

What is the TATA box?

Answer 7

The TATA box is a key DNA sequence often involved in initiating transcription in eukaryotes

Question 8

What are the three stages of transcription?

Answer 8

The three stages of transcription are initiation, elongation, and termination.

Question 9

What happens during the elongation stage of transcription?

Answer 9

During elongation, RNA polymerase unwinds the DNA, exposing about 10-20 base pairs at a time, and adds RNA nucleotides in the 5’ to 3’ direction to the growing RNA chain

Question 10

How does transcription terminate in bacteria?

Answer 10

In bacteria, transcription terminates when RNA polymerase transcribes a terminator sequence on the DNA, signaling the end of transcription.

Question 11

What is RNA processing in eukaryotes?

Answer 11

RNA processing in eukaryotes involves modifications to the primary RNA transcript, including the addition of protective caps and splicing.

Question 12

What is added to the 5’ end of the RNA during RNA processing?

Answer 12

A modified guanine nucleotide, known as the 5’ cap, is added to the 5’ end of the RNA.

Question 13

What is the purpose of the poly-A tail added to the 3’ end of the RNA?

Answer 13

The poly-A tail increases stability, facilitates nuclear export, and assists in translation initiation.

Question 14

What are introns and exons?

Answer 14

Introns are noncoding sequences in the RNA that are removed during RNA splicing, while exons are coding sequences that are joined together to form a continuous coding sequence.

Question 15

What is the spliceosome?

Answer 15

The spliceosome is a large protein-RNA complex that catalyzes the splicing process, removing introns and joining exons together.

Question 16

What is translation?

Answer 16

Translation is the process by which the genetic code in mRNA is used to synthesize a sequence of amino acids, forming a polypeptide.

Question 17

What are the key components involved in translation?

Answer 17

The key components involved in translation are mRNA, tRNA, and ribosomes.

Question 18

What is the role of tRNA in translation?

Answer 18

tRNA brings specific amino acids to the ribosome, matching its anticodon with the corresponding mRNA codon.

Question 19

What are the three binding sites on a ribosome?

Answer 19

The three binding sites on a ribosome are the P site, A site, and E site.

Question 20

What is the function of the site on a ribosome?

Answer 20

The P site holds the tRNA carrying the growing polypeptide chain.

Question 21

What is the function of the A site on a ribosome?

Answer 21

The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain.

Question 22

What is the function of the E site on a ribosome?

Answer 22

The E site is where discharged tRNAs exit the ribosome.

Question 23

What is the wobble hypothesis?

Answer 23

The wobble hypothesis suggests that the flexibility in the base pairing of the third nucleotide of the codon allows a single tRNA to bind with multiple codons.

Question 24

What are the three stages of translation?

Answer 24

The three stages of translation are initiation, elongation, and termination.

Question 25

What happens during the initiation stage of translation?

Answer 25

During initiation, the ribosome binds to the mRNA, and an initiator tRNA (carrying methionine) attaches, forming the initiation complex.

Question 26

What happens during the elongation stage of translation?

Answer 26

During elongation, the ribosome moves along the mRNA, and tRNA molecules bring amino acids to the ribosome according to the codon sequence, extending the polypeptide chain.

Question 27

What happens during the termination stage of translation?

Answer 27

During termination, the ribosome encounters a stop codon, releasing the completed polypeptide from the ribosome.

Question 28

What are post-translational modifications?

Answer 28

Post-translational modifications are changes made to the polypeptide after translation, such as the addition of sugars, lipids, or phosphate groups, and the removal of amino acids from the N-terminus.

Question 29

What is the role of signal peptides in protein targeting?

Answer 29

Signal peptides direct newly synthesized proteins to the endoplasmic reticulum for transport or secretion.