L1- Central dogma Flashcards
How does cell signalling lead to changes in gene expression?
Cell signalling impacts transcription that occurs in the nucleus by turning on and off specific genes
Changes in transcription lead to changes in translation and thus altered protein production
The altered protein changes cell function
What is a gene?
Unit of subsequent nucleotides (ATGC) which arranges together as a unit of information. It replicates during cell division.
How many megabase pairs long is the human genome?
3 mbp long
What percent of DNA codes for proteins?
About 2%
How long is the human genome in metres?
About 1.8m
How is DNA compacted in eukaryotes?
DNA double helix (2nm) is wrapped around an octamer of histones.
This forms a nucleosome (11nm).
Multiple nucleosomes join to form a chromere (30nm).
Multiple chromeres form chromatid fibres.
These are packaged into the familiar chromosome shape (1400nm)
What are the types of RNA polymerases?
RNA POLYMERASE 1- Transcribes 18S/28S rRNA
RNA POLYMERASE 2- Transcribes mRNA and few small RNA’S
RNA POLYMERASE 3- Transcribes tRNA, 5S rRNA and other small RNA’s.
How is transcription regulated by the promoter?
PROMOTER: Core binding region for transcription factors and RNA polymerases.
TATA BOX: Core element of promoter which promotes transcription and has a conserved sequence. Is 25 nucleotides upstream of transcription start site.
How is transcription regulated by the enhancer/silencer?
Regions before the promoter that increase/decrease transcription via binding factors
How is transcription regulated by methylation/histone acetylation?
Methylation inhibits transcription.
Acetylation increases transcription.
Deacetylation inhibits transcription.
How is mRNA processed post transcriptionally?
- Addition of a poly-A tail at the 3’ end of the mRNA increases stability in export.
Addition of a methyl-G cap at the 5’ end of the mRNA is recognised by RNA binding protein which aids in stability, transport, splicing and translation.
- Splicing of the mRNA removes the non-coding intron regions. RNA binding proteins modulate exon inclusion.
What happens in initiation of translation?
Initiation:
Ribosome binds the mRNA and a peptide bond forms between the first two amino acids. The 40S component of the ribosome binds to the 5’ cap on the mRNA and recognises AUG codon (initiation site). 60S component binds after this.
Poly-A tail at the 3’ end stimulates the formation of the initiation complex.
What happens in elongation of translation?
All reactions from the formation of the first peptide bond till the last amino acid was added.
What happens in termination of translation?
Release of the polypeptide chain while the ribosome dissociates from the mRNA.
What are the post translational modifications?
Folding of the polypeptide chain into the 3D protein structure (tertiary/quaternary structure) that determines its function.
Binding of cofactors to the polypeptide chain to aid it in its protein function.
Phosphorylation by kinases
