Chapter 7.2

Question 1

What two enzymes are involved in unwinding of the two strands of DNA during transcription?

Answer 1

-helicase and topoisomerase are involved in unwinding the double-stranded DNA and preventing the formation of supercoils

Question 2

What is the template strand also referred to as during transcription? What is the coding strand referred to as

Answer 2

• it is also referred to as the anti sense strand

- coding strand is referred to as the sense strand

Question 3

What is the main RNA polymerase involved in transcribing mRNA in eukaryotes

Answer 3

-it is RNA polymerase 2

Question 4

Which region does RNA polymerase 2 bind to when transcribing mRNA

Answer 4

• it binds to the region called TATA box

- >this region has a high concentration of thymine and adenine bases

Question 5

What are transcription factors? What are the roles of these factors?

Answer 5

• they help the RNA polymerase located and bind to the promoter region of the DNA
• > helps establish where transcription will start

Question 6

Does RNA polymerase like DNA polymerase require a primer to start generating transcript

Answer 6

-no

Question 7

Describe the different types of RNA polymerases in eukaryotes. Also mention their location.

Answer 7

1) RNA polymerase 1
- >located in the nucleolus and synthesizes rRNA

2) RNA polymerase 2
- >located in the nucleus
- >synthesizes hnRNA(pre-processed mRNA) and some small nuclear RNA(snRNA)

3) RNA polymerase 3
- >located in the nucleus
- >synthesizes tRNA and some rRNA

Question 8

Is there proofreading done by the RNA polymerase?

Answer 8

-no there is no proofreading

Question 9

What is the relation of the coding strand to the mRNA strand

Answer 9

• they are identical
• because the coding strand is complementary to the anti sense strand or the template strand
• there is a difference between the coding and mRNA strand
• > that is the mRNA strand has all the thymine nucleotides replaced with uracil ones

Question 10

Describe the structure of the spliceosome.

Answer 10

• there is small nuclear RNA

- this is coupled with small nuclear ribonucleoproteins

Question 11

Describe the 5’-cap structure. What is its function

Answer 11

• it is a 7-methylguanylate triphosphate cap
• > it is added during the process of trnascription

-its function is to protect the mRNA from degrading in the cytoplasm

Question 12

Describe the 3’ Poly-A-Tail. What is its function

Answer 12

• it is added to the 3’ end of the mRNA transcript
• > composed of adenine bases
• its function is to protect the mRNA from rapid degradation
• > it almost serves as a time bomb

Question 13

What is the purpose of alternative splicing

Answer 13

• it is used to make different amount of proteins from a limited number of genes
• it is also known to regulate gene expression in addition to generating protein diversity