Unit 1: Transcription

Question 1

What is the central dogma ?

Answer 1

A digram showing how info flows from DNA–> RNA—> Proteins

Question 2

What are the 3 types of RNA polymerases in eukaryotes ?

Answer 2

1) Pol 1
2) Pol 2
3) Pol 3

Question 3

Where is RNA polymerase pol 1 found ?

Answer 3

In ribosomal RNAs to be used in translation

Question 4

Where is RNA polymerase pol 2 found ?

Answer 4

In mRNA for translation into proteins

Question 5

Where is RNA polymerase pol 3 found ?

Answer 5

In small RNAs such as tRNA

Question 6

What are the 3 steps of RNA synthesis ?

Answer 6

1) Initiation
2) Elongation
3) RNA processing and termination

Question 7

Transcriptional initiation is a major way of …..?

Answer 7

Regulating gene expression

Question 8

Free nucleotides are always added at what end ?

Answer 8

The 3’ to 5’

Question 9

What is the RNA sequence the same as ?

Answer 9

The coding strand

Question 10

What is the difference between the coding strand and the RNA sequence ?

Answer 10

Uracil is used instead of thymine

Question 11

What DNA strand is complementary to the RNA sequence ?

Answer 11

The template strand

Question 12

What is the promoter region responsible for attracting ?

Answer 12

General transcriptional factors- they recognise sequence close to start site

Question 13

What is the function of TBP ?

Answer 13

It recognises TATA protein and therefore binds to it attracting other TFs to form a preinitiation complex

Question 14

What is needed aswell as general TFs ?

Answer 14

Gene specific TFs

Question 15

What can gene specific TFs do ?

Answer 15

Can bind at other sequences that are close to promotor sequence

Question 16

What is the ‘velcro’ model ?

Answer 16

• Model to show roles of TFs
• Multiple places where sequence specific binding proteins are binding to sequence
• Through combination of protein-protein interactions, RNA polymerase 2 is attracted

Question 17

What are the 2 grooves found in helical DNA called ?

Answer 17

• Major groove
• Minor groove

Question 18

Where are the major and minor groove located ?

Answer 18

On opposite sides of the helix to one another

Question 19

What are 4 structural motifs often found in TFs ?

Answer 19

1) Helix-Turn-Helix
2) Zinc finger
3) Leucine zipper
4) Helix-Loop-Helix

Question 20

What is the structure and function of helix-turn-helix ?

Answer 20

Two alpha helices connected by a short turn, enabling the protein to bind to specific DNA sequences and regulate gene expression

Question 21

What is the structure and function of zinc finger ?

Answer 21

It is a protein motif that coordinates a zinc ion to stabilize its structure, which enables it to bind specifically to DNA

Question 22

What is the Leucine zipper ?

Answer 22

It is a protein motif that enables dimerization of transcription factors through hydrophobic interactions between leucine residues

Question 23

What is the structure and function of helix-loop-helix ?

Answer 23

The motif consists of two alpha helices connected by a flexible loop, and is a protein structure that enables dimerization and DNA binding

Question 24

What is topoisomerase ?

Answer 24

An enzyme that plays a critical role in the supercoiling and unwinding of DNA during processes like DNA replication, transcription, and repair

Question 25

What is elongation ?

Answer 25

• Process to make DNA single stranded
• Requires topoisomerase and rudder

Question 26

How is a 5’ cap added and what is its purpose ?

Answer 26

• A single 7-mythyl guanosine is attached to the first nucleotide by a triphosphate linkage
• This causes the 2 phosphate groups on the 5’ ends to bond to each other
• Protects ends from degradation
• Aids in initiation of protein synthesis

Question 27

What are SNRAs?

Answer 27

Small nuclear RNAs that are essential components of splicesome

Question 28

What is splicing ?

Answer 28

When introns are removed from pre-mRNA so that it can become mature mRNA

Question 29

What is alternative splicing ?

Answer 29

• It is a process that allows a single gene to generate multiple mRNA variants, by selecting different splice sites during pre-mRNA processing
• This increases the diversity of proteins in a cell and allows for more precise regulation of gene expression