Transcription

Question 1

Rna polymerase

Answer 1

is a multi-unit enzyme that is responsible for creating a complementary strand of nucleic acid, called RNA, from a single-stranded DNA template through the incorporation of adenosine, cytosine, guanine and uracil nucleotides

Question 2

3 types of rna polymerase

Answer 2

• RNA Pol 1: makes ribosomal RNA*
• RNA Pol 2: makes most RNA transcripts, including mRNA and microRNA • RNA Pol 3: makes tRNA, 5S rRNA and other small RNAs.

Question 3

Types of rna

Answer 3

• mRNA: messenger RNA (protein coding) • rRNA: ribosomal RNA*
• tRNA: transfer RNA*
• miRNA: micro RNA
• lncRNA: long non-coding RNA

Question 4

Promoter

Answer 4

• A promoter is a region of DNA where relevant proteins (such as rna polymerase ans transcription factors )bind to initiate transcription of a gene
• Promoters control the binding of RNA polymerase to DNA.
• Most protein coding genes contain a TATA Box
• Transcription start site (TSS)

Question 5

How does RNA Polymerase know where in the genome to start transcription?

Answer 5

Transcription factors
Promoters
Tata box

Question 6

General transcription factors

Answer 6

TFIID
Recognizes TATA box and other DNA sequences near the transcription start point (TSS)
TFIIB
Binds TFIIB response element (BRE) in promoters; accurately positions RNA polymerase at the start site of transcription (TSS)
TFIIA
Not required in all promoters; stabilizes binding of TFIID
TFIIF
Stabilizes RNA polymerase interaction with TFIIB; helps attract TFIIE and TFIIH
TFIIE
Attracts and regulates TFIIH
TFIIH

Question 7

Transcription Initiation

Answer 7

-General transcription factors recruit RNA Polymerase to form a pre-initiation complex

-Chromatin modifiers and enhancer proteins are also necessary for transcription to begin

Question 8

Sense or anti sense factors

Answer 8

They are complimentary
Antisense strand generates sense rna
Sense strand genres antisense rna

Question 9

Sense or anti-sense

Answer 9

One strand of DNA is called the sense strand because when you read it in the right direction it provides the code to make a protein. In two-stranded DNA, the sense strand is bonded to an opposite DNA strand that is called the antisense or noncoding strand.

Question 10

Termination

Answer 10

• RNA transcripts are processed while transcription is still progressing
• Mature RNA is capped at the 3’ End
• RNA polymerase will stop transcribing sometimes 100s of bases after the 3’ untranslated region

-1. RNA Pol reaches a “T-tract” in DNA template
2. Torpedo protein causes release pf RNA Polymerase

Question 11

Torpedo” model:

Answer 11

RNA Pol stopped by another protein

Question 12

RNA Pol stopped by another protein

Answer 12

RNA stopped due to a change in shape

Question 13

Initiation, elongation and termination summary

Answer 13

Initiation
• RNA Polymerase is recruited to the TSS by transcription factors
• A transcription bubble is formed by unwinding the DNA template
Elongation
• RNA Polymerase uses the DNA as a template • RNA transcripts are made from 5’ to 3’
• New nucleotides are added to the 3’ end
Termination
• RNA drops off the DNA template – how? why? where? • Mechanisms are not yet fully understood

Question 14

Regulation of gene expression

Answer 14

Eukaryotic gene expression can be controlled:
1) In the nucleus, as the RNA is transcribed from the DNA, transcription control regulates when and how often a given gene is transcribed.
2) RNA processing control occurs when the RNA transcript is processed into an mRNA.
3) RNA transport and localization control regulates which completed mRNAs are exported from the nucleus to the cytosol and determines where in the cytosol the mRNAs are localized.
4) In the cytoplasm where the mRNA is either degraded or translated by the ribosome to build a protein*
5) Protein function and degradation are also tightly controlled