lecture 3 : gene organisation + transcription Flashcards Preview

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Flashcards in lecture 3 : gene organisation + transcription Deck (18)
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1
Q

what are the main differences between DNA and RNA?

A
  • RNA uses the sugar ribose instead of deoxyribose - deoxyribose has one less oxygen molecule than the ribose sugar - RNA is generally single stranded instead of double stranded - RNA contains uracil in place of thymine
2
Q

what are ribonucleotide bases joined by?

A
  • they are joined by phosphodiester bonds
3
Q

in what direction does the RNA chain grow?

A

it grows from 5’- 3’ direction

4
Q

what is an antisense strand?

A

this is the DNA strand that gets transcribed (it is antisense because it is the opposite of the RNA that is produced)

5
Q

what carries out transcription?

A
  • RNA polymerases
6
Q

what else is involved with transcription?

A
  • special gene regulatory factors called transcription factors
7
Q

what are the three types of RNA polymerase and what do they do?

A

RNA polymerase i : transcribes rRNA genes

RNA polymerase ii : transcribes mRNA

RNA polymerase iii : transcribes genes encoding protein into tRNA

8
Q

how is gene regulation achieved?

A
  • DNA synthesis needs an initiation phase first to build the transcription complex - the DNA sequence at where the transcription complex assembles is called the gene promotor (TATA) - the amount of transcription of a gene is regulated by the activity of DNA binding proteins = transcription factors e.g. (TATA binding protein) - transcriptional activators activate the gene activity - transcriptional repressors surprise the gene expression
9
Q

* what does the basal transcription complex do? and what is the basic anatomy? what is TF iiD?

A

it produces a low level of transcription in the absence of other transcription factors - also allows RNA polymerase ii to be phosphorylated and then engage in transcription this is TATA binding protein and accessory factors this binds to TATA

10
Q

* what is the first step of the basal transcription complex?

A

TF iiD binds to TATA binding site insert image

11
Q

what happens when TF iiD binds to TATA and the accessory factors?

A
  • partially unwinds the DNA and widens the minor groove … this allows extensive contact with the bases - the unwinding is asymmetrical with respect to TBP- TATA complex - this means the transcription is unidirectional
12
Q

* what is the second stage of the basal transcription complex? why is this important?

A

insert pic the TF iiA and TFiiB also bind to the TATA (transcription factor) TF

13
Q

what is the third stage of basal transcription complex?

A

insert the pic the RNA polymerase ii binds to the TF iiB and then TFiiF binds to the RNA polymerase ii

14
Q

what is the fourth stage of basal transcription complex?

A

insert the pic this is when TF iiE, TF iiH and TF iiJ all bind to RNA polymerase ii

15
Q

why is TF ii H important?

A

this promotes further unwinding of the DNA helix to allow the RNA synthesis by RNA polymerase ii

16
Q

how do transcription factors act?

A
  • they bind to the transcription factor binding sites and bend the DNA - they interact with one another and the basal transcription complex to modulate the transcription - they allow transcription by helping to remodel chromatin and this is done by recruiting protein enzymes to modify histones
17
Q

what is hyperacetylation? what is Hypoacetylation?

A

hyperacetylation = gene expression (hyper) Hypoacetylation= gene repression

18
Q

what factors determine transcription factor expression

A
  • cell lineage - transcription factor expression is altered by signals outside the cell - mutated transcription factors have been implicated in several human genetic disorders - abnormal transcription factor expression is found in several human factors