Transcription

Question 1

What is transcription?

Answer 1

process of copying a gene’s DNA sequence into mRNA

Question 2

What are the 3 steps of transcription?

Answer 2

1. Initiation
2. Elongation
3. Termination

Question 3

What is initiation?

Answer 3

Process where RNA polymerase binds to the promoter region of DNA and begins RNA synthesis

Question 4

Where does transcription begin?

Answer 4

Begins at a promoter which is a sequence of DNA

Question 5

What are transcriptional factors?

Answer 5

They mediate the binding of RNA polymerase and the initiation of transcription

Question 6

What is the transcription initiation complex?

Answer 6

The completed assembly of transcription factors and RNA polymerase II bound to a promoter

Question 7

Where does transcription begin in eukaryotes?

Answer 7

At the TATA box

Question 8

What is elongation?

Answer 8

RNA polymerase moves along the DNA, synthesizing the RNA strand by adding complementary RNA nucleotides

Question 9

What is a transcription bubble?

Answer 9

the unwound section of DNA during elongation, exposing 10-20 bases at a time for RNA synthesis

Question 10

In which direction does RNA polymerase synthesize mRNA?

Answer 10

mRNA is synthesized in the 5’ to 3’ direction

Question 11

What is termination?

Answer 11

RNA polymerase releases the RNA strand and detaches from the DNA after reaching a stop codon

Question 12

Termination - Prokaryotes

Answer 12

• RNA polymerase stops transcription at stop codon
• mRNA can be translated without further modification

Question 13

Termination - Eukaryotes

Answer 13

• RNA polymerase II transcribes a polyadenylation signal sequence
• RNA transcript is released 10-35 nucleotides past this sequence

Question 14

What is a polyadneylation signal?

Answer 14

• It signals the termination of transcription and addition of a poly-A tail to the mRNA
• AAUAAA

Question 15

What are ribozymes

Answer 15

Catalytic RNA molecules that function as enzymes

Question 16

Why are introns important?

Answer 16

They can contain sequences that might regulate gene expression or include promoter elements

Question 17

What is alternative RNA splicing?

Answer 17

It allows genes to encode multiple polypeptides by varying which segments are treated as exons during splicing

Question 18

What are protein domains?

Answer 18

molecular architecture consisting of discrete regions in proteins

Question 19

What do individual exons code for in a protein?

Answer 19

They code for different domains in a protein

Question 20

What is exon shuffling?

Answer 20

The rearrangement of exons, potentially leading to the evolution of new proteins

Question 21

3 parts of mRNA processing

Answer 21

1. 5’ Cap is placed on the 5’ end of mRNA
2. Poly-A Tail is placed on 3’ end of mRNA
3. Introns are spliced out

Question 22

5’ Cap Functions

Answer 22

Provides protection to the 5’ end

Question 23

Poly-A Tail Functions

Answer 23

Protects 3’ end from degradations and helps ribosomal attachment