W1 L2 gene structure, organization and regulation Flashcards
Prokaryotic cell component
- plasma membrane
- DNA
- Ribosome
- Cell wall
- Flagelum
Factors influencing genome size
! Genes
! Gene density (intergenic regions)
! Introns (size and number)
! Repeats
How does our gene fit inside the nucleaus
It is structured to fit inside a nucleus
DNA is wrap in Optimus of histone which are folded upon itself, creating a condense section of chromosome
This affect the gene availability to be transcribe
Nuclear structure
- Highly structured of active and repressed gene expression
-DNA and associated proteins along side RNA
Genes to Gene Products
The DNA is transcript into mRNA via RNA polymerase
mRNA is translated by the ribosome into protein
RNA Polymerases in eukaryote, their shared and different structure
We use DNA dependent RNA polymerase
! Three kinds in eukaryotes, each have alpha and beta subunit or alpha like and beta like in eukaryote one
Shared common subunit
Each have additional enzyme specific subunit (1-5,2-4,3-7)
Three fuction of the DNA polymerase
mRNA
Messenger RNA code for protein
rRNA
ribosomal RNA, forms basic structure of ribosome and catalyst protein synthesis
tRNA
transfer RNA, centrals to protein synthesis as adaptor between mRNA and amino acids
snRNA
small nuclear RNAs, fuction in a variety of nuclear process including slicing pre mRNA
snoRNA
small nucleolar RNAs , use to chemically modify rRNA
scaRNAs
Use to modify sno and sn
miRNA
Micro RNA, regulate gene expression typically by blocking translation of selective mRNA. single stranded
siRNA
Small inferring RNA, Turn off gene expression by directing edge radiation of selective mRNA and the establishment of compact chromatin structure. double stranded
Transcription steps at class 2
! 1. Formation of the pre-initiation complex
2. Promoter melting separation of the two DNA strands
! 3. Initiation
! formation of the first phosphodiester bond in the nascent mRNA
! 4. Promoter clearance
! 5. Elongation
! 6. Termination
what is involve in the Initiation of transcription
There are many elements that is involve in the initiation, these need to be present for decent transcription rate
Each promoter contains a subset of these elements
e.g. TATA and Inr
! Each element is recognized by a general transcription factor (GTF), not RNA pol II
What happen when gene does not have promoter element
! These genes often are transcribed at low rates
! Are so-called housekeeping genes
! Have multiple transcription start points
! Contain CG-rich sequences (CpG islands)
General Transcription Factor TFIID structure and fuction
Contains:
! TATA binding protein (TBP)
! TBP associated factors (TAFs)
! Binds core promoter elements and initiates assembly of the pre-initiation complex (TFIID, transcription factors and RNA Pol II) on the promoter
Other General Transcription Factor
TF2B for accurate positioning
TF2F to stablise and TBP and TF2B, attract other TF
TF2 E attract and regulate TF2H
TF2H unwind DNA at start point and release RNA polymerase
Core RNA pol complex and GTFs Of Genes transcribed by RNA Pol I
Recognises Upstream Control Sequence (UCS)
! Selective Factor SL1/TIF-1B include TBP as a component
! Upstream Binding Factor (UBF) recognises UCS
! Rrn3/TIF-IA recruit SL1/UBF to RNA pol
Ribosomal RNA (rRNA) genes (except 5S – Pol III) Of Genes transcribed by RNA Pol I
! Repeated clusters of rDNA repeat unit
! Each is transcribed into a pre-rRNA precursor which is processed into 18S, 5.8S and 28S rRNAs
! Transcription occurs in the nucleolus (where ribosomes are assembled)
