Ch 14 Gene Expression: From Gene to Protein Flashcards
where does transcription occur in cell
nucleus
how does transcription start
binding of RNA polymerase to promoter in DNA
what is required for transcription to occur
- tata box (promoter)
- RNA polymerase 2
- Transcription factors
how many H-bonds between A-U
two
features of mature mRNA
- 5’ prime cap
- 3’ end get poly A tail
- exons spliced together and introns cut out
where does translation occur in cell
cytoplasm
how does translation start
binding of ribosome, starts at AUG codon
how does translation terminate
when stop codon in mRNA reaches A site of ribosome, site accepts prone release factor–> causes add-on of H2O instead of a.a. reaction then real seas polypeptide and translation assembly comes apart
what are the components of translation machinery
need tRNA
amino acyl tRNA synthase
ribosome (large+small subunit)
structural features of tRNA
transfers amino acid to polypeptide in ribosome
what are the steps of elongation cycle of translation
- codon recognition
- peptide bond formation
- translocation
Codon recognition of elongation
amino acid added one by one to previous amino acid at c-terminu of growing chain
translocation of elongation
happens along mRNA in 5’–>3’ direction
what are the features of genetic code
- red in triplets “codons”
- composed of 4 nucleotides on mRNA
- 64 possible combos
what is a codon
sequence of three nucleotides that together form unit of genetic code in DNA/RNA molecule
Types of mutations
Frameshift: insertion and deletion
Point mutation
Substitution: silent, missense, non-sense
Silent mutation
have no effect on amino acids produced by codon b/c redundancy in genetic code
Missense mutation
code for amino acid but not correct amnio acid
Non-sense mutation
change a.a codon into stop codon almost always using non-functional protein
Frameshift mutations
caused by deletion/insetion in DNA sequence that shifts the way a sequence is read
mutagens
agent that causes genetic mutation (radiation)
