transcription and gene expression Flashcards
RNA
-DNA sequence copied so proteins can be produced from it
-mRNA used as templates to code for proteins
number of protein coding genes
20,000 protein coding genes in a human genome not all these proteins are present at the same level and time in all cells so we need regulate gene expressio. aim of a drug treatment is to regulate gene expression
regulation of gene expression happens at various different steps
-regulation of transcription
-regulation of mRNA (eg. it gets spliced) processing and decay
-regulation of translation
(how long does the protein last aswell)
RNA structure
secondary
-harpin
-stem loops
Tertiary structures
-knots and loops
this effects translation as it changes how long it lasts and how well it can be used
RNA stability
rna is chemically less stable than DNA, especially under alkaline conditions. cause the sugar can get attacked bu OH and form water. its usually single stranded compared double stranded DNA. but can make diverse structures and enzymes because its single stranded.
how does RNA polymerase know when to start
-doesnt need a primer as the DNA sequence has. a promoter region that directs RNA polymerase to the right spot
-transcription factors (they are DNA binding proteins) recruit RNA polymerase to the promoter region
how to regulate transcription:
change how accessible chromatin is to RNA polymerase
- chromatin rearrangement: changes how accesesible the DNA template is to RNA polymerase, change in nucleosome density open up TATA box
basal transcription bind to TATA box, there are some that are specific
-can regulate transcription factors, that compete with histones and they recognise different sequences of DNA (bind to promoter sequences)
Transcription factors can bring in other things like coactovaters which can cause the acetylation of histone proteins which makes the DNA sequence exposed
nucleosome code is long lasting
-this is important because you don’t want the genes expressed to change during replication. so chromatin modifications stay to lock and expose genes. so the modifications are kept through replication
-can somties be passed through generations study of this is called epigenetics
