Transcription

Question 1

What is the flow of the Central Dogma of Molecular Biology

Answer 1

It is a theory that states that genetic information only flows in one direction: DNA makes RNA, RNA makes proteins. Or, RNA directly to proteins

Question 2

What are the macromolecules involved in the Central Dogma of Biology and their roles

Answer 2

DNA - Storage of genetic information
RNA - Messenger of genetic information
Proteins - Workers/implementers of genetic information

Question 3

What is transcription and translation

Answer 3

Transcription is the transcribing to the template strand of DNA to synthesis a complimentary strand of messenger RNA
Translation is the translation of the messenger RNA into a protein via polypeptide chain synthesis at a ribosome

Question 4

What is gene expression

Answer 4

The process by which information from a gene is used in the synthesis of a functional gene product (a protein or non coding RNA)

Question 5

What is non coding RNA

Answer 5

An RNA molecule that will not give rise to a protein and has some other function

Question 6

What is a gene

Answer 6

A defined region (sequence) of DNA that produces a type of RNA molecule that has some function
May contain sequences responsible for regulation of the syntheses of RNA, sequences that produce RNA, and sequences responsible for the further processing of RNA

Question 7

What enzyme catalyses transcription, and what does it do

Answer 7

RNA polymerase
RNA polymerase synthesis mRNA by catalysing formation of phosphodiester bonds between ribonucleotides
It selects the correct nucleotides to incorporate based on the sequence of the DNA which is being transcribed

Question 8

What are the two DNA strands, and which is transcribed

Answer 8

DNA has two complimentary strands
The coding strand (5’ to 3’), and the template strand (3’ to 5’)
RNA polymerase transcribes the template strand to produce a strand of mRNA complimentary to the template strand, and Identical to the coding strand

Question 9

What are the 3 stages of transcription

Answer 9

Initiation
Elongation
Termination

Question 10

Outline the initiation step

Answer 10

Transcription factors bind to the TATA rich region, and other regions of the promoter
RNA polymerase 2 binds, forming a transcriptional initiation complex with the transcription factors
The two DNA strands seperate and RNA polymerase 2 starts mRNA synthesis without the need of a primer

Question 11

Why can RNA polymerase 2 being transcription without a promoter

Answer 11

RNA polymerase 2 has an internal 3’ hydroxyl group allowing it to being translation on its own

Question 12

What releases tension in the DNA strand caused RNA unzipping it

Answer 12

Topoisomerase

Question 13

Outline the elongation step

Answer 13

RNA polymerase 2 uses the template strand, which runs 3’ to 5’, as a template and inserts complimentary RNA nucleotides in the 5’ to 3’ direction. mRNA synthesis is anti parallel to the template strand

Question 14

Which part of the gene is transcribed from DNA into mRNA

Answer 14

The 5’ UTR, the Coding Sequence, and the 3’ UTR

Question 15

Which parts of the gene are translated from mRNA to protein

Answer 15

The coding sequence

Question 16

What is the function of a promoter region

Answer 16

It is a DNA segment that is recognised by RNA polymerase to initiate transcription

Question 17

What region of the promoter region is particularly important and why

Answer 17

The TATA rich region
AT (adenine bond thymine) are bound by two hydrogen bonds, compared to the 3 hydrogen bonds of GC (guanine bond cytosine). Hence a AT bond rich region will be easier to seperate than one that is not. This allows RNA polymerase to easily seperate the coding and template DNA strands, to then subsequently begin transcription

Question 18

What are the main functions of UTRs

Answer 18

Regulatory elements that influence gene expression at the transcriptional or translational level.
5’ UTR facilitates the addition of a 5’ G Cap
3’ UTR facilitates the addition of the Poly A Tail

Question 19

What is the function of the 5’ G cap

Answer 19

It prevents mRNA degradation, promotes intron excision, and provides a binding site for the small ribosomal sub unit

Question 20

What is the function of the Poly A Tail

Answer 20

It prevents mRNA degradation and facilitates the export of mRNA from the nucleus to the cytoplasm

Question 21

Why are mutations in the non coding regions harmful

Answer 21

By altering the non coding region, a variant in non coding DNA can turn on a gene and cause a protein to be produced in the wrong place or at the wrong time. Alternatively, it could reduce or eliminate the production of the desired protein when and where it is needed

Question 22

What are eukaryotes, prokaryotes, and where does transcription and translation occur in them respectively

Answer 22

Eukaryotes are a domain of organism whose cells have a nucleus. Transcription occurs in the nucleus, and translation occurs in the cytoplasm. Transcription and translation are not coupled.
Prokaryotes are a domain of organism whose cells lack a nucleus, and other membrane bound organelles. Transcription and translation occur in the cytoplasm. Transcription and translation are coupled.