Biochemistry Chapter 7: RNA and the Genetic Code Flashcards
What is the central dogma of biochem?
DNA - RNA - protein
What is the start codon?
AUG
What are the stop codons?
UGA, UAA, UAG
What allows mutations to occur without effects in the protein?
redundancy and wobble
Silent mutations
no effect on protein synthesis
Nonsense mutations
produce a premature stop codon
Missense mutation
produce a codon that codes for a different amino acid
Frameshift mutations
result from nucleotide addition or deletion & change the reading frame of subsequent codons
Differences in RNA from DNA
- ribose sugar
- uracil instead of thymine
- single-stranded
mRNA
carries the message from DNA in the nucleus via transcription of the gene; travels into the cytoplasm to be translated
tRNA
brings in amino acids, recognizes the codon on the mRNA using its anticodon
rRNA
makes up the ribosome
Helicase and topoisomerase
Unwind the DNA double helix
RNA polymerase II
Binds to the TATA box within the promoter region of the gene
hnRNA
synthesized from the DNA template antisense strand
What are some posttranscriptional modifications?
- 7-methylguanylate triphosphate cap is added to the 5’ end
- Poly A tail is added to the 3’ end
- splicing
How can prok and euk increase variability?
Prok - polycistronic genes
Euk - alternative splicing
What are the three steps of translation?
Initiation
Elongation
Termination
What starts initiation in prok?
30S ribosome attaches to the Shine-Dalgarno sequence
What starts initiation in euk?
When the 40S ribosome attaches to the 5’ Cap and scans for a start codon
What are some posttranscriptional modifications
- folding by chaperones
- formation of quarternary structure
- cleavage of proteins or signal sequences
- covalent addition of other biomolecules
