Transcription

Question 1

What happens during transcription?

Answer 1

A gene is copied into an RNA nucleotide sequence.

Question 2

In transcription a small portion of ___ is opened and unwound to ______ the bases on each DNA strand. One of the two strands acts as a _________ for the synthesis of ___.

Answer 2

In transcription a small portion of **DNA **is opened and unwound to **expose **the bases on each DNA strand. One of the two strands acts as a template for the synthesis of RNA.

Question 3

What are the enzymes that carry out transcription?

Answer 3

DNA polymerases

Question 4

What do the majority of genes in a cell’s DNA code for?

Answer 4

Proteins

Question 5

What are RNA molecules copies from coding genes called?

Answer 5

messenger RNA (mRNA) molecules

Question 6

What are the types of RNA polymerases in eukaryotes?

Answer 6

RNA polymerase I, II, and III

Question 7

Which polymerases transcribe genes encoding tRNA and rRNA?

Answer 7

Polymerase I and III

Question 8

What does polymerase II transcribe?

Answer 8

Most genes (all that include proteins)

Question 9

Eukaryotic RNA polymerases require many additional proteins, collectively called the ________ _________ _________.

Answer 9

Eukaryotic RNA polymerases require many additional proteins, collectively called the general transcription factors.

Question 10

What do general transcription factors do?

Answer 10

They help to:

• **Position **RNA polymerase correctly at the promoter
• Aid in pulling apart the two strands of DNA to allow transcription to begin
• Release RNA polymerase from the promoter into the elongation mode once transcription has begun

Question 11

How much of the human genome is occupied by protein-coding genes?

Answer 11

3%

Question 12

What base is **thymine **replaced with?

Answer 12

Uracil

Question 13

Define TATA box

Answer 13

A DNA sequence that indicates where a genetic sequence can be read and decoded.

Question 14

The assembly of the transcription initiation complex begins when *what *binds to the TATA box?

Answer 14

TFIID

Question 15

Where is the TATA box located?

Answer 15

25-35 nucleotides upstream of the transcription start site

Question 16

What happens after TFIID binds to the TATA box?

Answer 16

The binding causes distortion in the DNA, other factors then assemble to form a complete transcription initiation complex

Question 17

What makes up the transcription initiation complex?

Answer 17

• TFIID
• TFIIB
• RNA polymerase II
• other factors
• TFIIE
• TFIIH

Question 18

What does TFIID do?

Answer 18

It contains DNA helicase and hydrolyses ATP to unwind the double helix

Question 19

What upstream regulatory elements are there?

Answer 19

• GC box
• CAAT box

Question 20

As well as upstream regulatory elements, what other control elements are there?

Answer 20

Enhancers and silencers

Question 21

What elements are needed to activate transcription in a eukaryotic cell?

Answer 21

• Activators
• Repressors
• Coactivators
• Basal factors (positions polymerase)

Question 22

What modifications are made after transcription?

Answer 22

• RNA splicing
• 5’ capping (7-methyl guanosine)
• 3’ polyadenylation

Question 23

How is mRNA capped?

Answer 23

• gamma phosphate lost
• GMP added
• methylation of nitrogen arom 7 of guanosine and of carbon 2’ of ribose

Question 24

What are the coding sequences of DNA called?

Answer 24

Exons

Question 25

What are non-coding pieces of DNA called?

Answer 25

Introns

Question 26

At what point is RNA termed mRNA?

Answer 26

After splicing out introns

Question 27

What carries out RNA splicing?

Answer 27

The spliceosome

Question 28

What forms the core of the spliceosome?

Answer 28

**snRNA(small nuclear RNA). **The rest is made from protein and RNA

Question 29

Define isoform

Answer 29

any of several different forms of the same protein