Lecture 8 Flow of genetic information Flashcards
from DNA to protein
DNA (replication, repair, recombination) -> RNA (transcription) -> protein (translation)
genes not transcribed equallt
RNA
ribose instead of deoxyribose
U (Uracil) instead of T (Thymine)
single-stranded, can create secondary structures
mRNA, tRNA, rRNA
RNA polymerase
enzyme synthesizing RNA, three different types in Eukarya
holoenzyme
RNA polymerase (core) + sigma-factor
needs to form in order to start the transcription
transcription
DNA, RNA pol, mRNA
promoter
DNA sequences that mark the initiation of transcription (recognized by RNA pol holoenzyme)
if transcription starts at +1, promoter sequences are at postions -35 and -10
variations in the space between (15-19 nt) gives promoters different strength
initiation of transcription
The polymerase needs trancription factors.
RNA Pol II needs the general trancription factors that help:
- Find and identify the promoter
- Position the polymerase correctly
- Help with the local DNA denaturation
- Change the polymerase to the elongation mode when needed
measure of how much our GOI is expressed
the GOI is replaced by a reporter gene (coding for a fluorescent protein), still under the control of the promoter that normally controls the GOI
measure expression of all genes
RNA seq - diff samples of isolated mRNA - see how many copies that are sequenced - ratio DNA microarray - diff samples of mRNA - converted to ctDNA and labeled with fluorochrome - hybridized to microarray - see level of expression based on color
transcripts in Bacteria vs Eukarya
bacteria simple
Euakarya involves splicing
transcription inside the nucleolus, translation in the cytoplasm
5’ cap and poly-A tail
processing factors
The CTD of RNA polymerase brings in different processing factors as transcription goes on
Different phosphorylation patterns of
CTD attract different processing factors
at different times
operon
genes that are transcribed together are called operons
gene organisation
picture
splicing
- only in Euakarya
- cut out of the introns
- done by the spliceosome, recognize specific sequences to catalyze the splicing reaction
Introns always start with … and end with …
GU
AG
Polyadenylation
For:
- Stability
- Nuclear transport
- Translation
mR NA goes to the … to be translated
cytoplasm
translation
Synthesis of the polypeptide chain, based on the mRNA transcript.
The synthesis is carried out on ribosomes.
Amino acids needed to build the protein are transported to the ribosome by tRNAs
codons/anticodons
Ribosome “reads” the genetic code
Codons on mRNA and ”read” by anti-codons on tRNA tRNAs bring in amino acids
Each amino acid corresponds to one or more codons
Aminoacyl tRNA stynthetases
amino acid + tRNA + ATP → aminoacyl-tRNA + AMP + PPi
Ribosome
picture
stop codon
UAA
UAG
UGA
When a stop codon comes along, relase factor binds instead of a tRNA, translation stops, and the ribosome dissociates
Polyribosome (polysome)
A series of ribosomes simultanously translates a eukaryal mRNA. Note the important position of cap- and polyA-associated proteins
proteasome
enzyme digesting incompletely folded protein
