Genetic code and Transcription I Flashcards
who coined the central dogma?
Francis Crick
reverse transcription
“backwards” flow of genetic info
-make DNA from RNA template
reverse transcriptase
enzyme that catalyzes the process of reverse transcription
coding sequences that code for unique polypeptide chains
alternative splicing
enhances the adaptability of the coding system
degenerate (>1 triplet)
each nucleotide is a part of one triplet
non-overlapping
codon
nucleotide triplet in mRNA
unambiguous (genetic code)
each codon specifies a particular amino acid
evidence for triplet nature of genetic code provided by who?
Crick and Brenner
open ready frame
causes frameshift mutations
-contains no stop codons
reading frame
sequence of consecutive, non-overlapping triplets
start codon examples (2)
AUG, MET
stop codon examples (3)
UAA, UAG, UGA
third base of codon frequently does not change the specified amino acid, T or F?
True
4 stages of transcription of mRNA from DNA
- binding
- initiation
- elongation
- termination
sigma factor
promotes binding of RNA polymerase to specific DNA sequences
when does initiation of RNA synthesis take place?
once the DNA is unwound
transcription in bacteria (4 steps)
- RNA polymerase binds to sigma factor
- initation of synthesis
- enlongation
- termination (GC loop, or rho factor)
bacterial promoter sequence (3)
- start point +1
- TATAAT box: -10 sequence
- -35 sequence
U-RNA (3)
- processes pre-mRNA in the nucleus
- aids in regulation of transcription factors
- maintains the telomeres
miRNA
small non-coding RNAmolecule
-regulation of gene expression
3 classes of eukaryotic promoters
RNA polymerase I, II, III
RNA polymerase I
- core promoters
- upstream control element
- improves promoter’s efficiency
RNA polymerase II
-4 DNA sequences
- short initiator
- TATA box
- TFIB recognition element (BRE)
- downstream promoter element (DPE)
upstream control elements (2)
- CAAT box
- GC box
proximal control elements
those within 100-200 nucleotides o the start point
enhancer elements
control elements more than 200 nucleotides from he start point
RNA polymerase III
upstream promoter used for transcribing small RNA molecules
RNA polymerase III promoter
entirely downstream from the start point
-for transcribing tRNA and 5S-rRNA