Nucleic acids Flashcards
(3 cards)
description of translation
1 two codons at a time are exposed (to the large subunit) ;
2 (idea of) a specific tRNA brings a specific amino acid ;
3 a tRNA anticodon binds to the mRNA codon ;
4 complementary base pairing occurs (by hydrogen bonding) ;
5 a second tRNA brings another amino acid (next to the first amino acid) ;
6 peptide bond formation between the two amino acids ;
7 ribosome moves along the mRNA, one codon at a time / and next codon is ‘read’ ;
8 the first tRNA leaves the ribosome ;
9 AVP ; e.g. first codon is always AUG
first anticodon is always UAC
first amino acid is always methionine
ribosome moves along mRNA in a 5’ to 3’ direction
role of peptidyl transferase
eventually a stop codon is reached (and translation stops)
DNA replication
1 double helix unwinds, qualified ; e.g. using, enzyme / helicase
breaking hydrogen bonds between strands
2 both strands act as templates ;
3 ref, activated (free DNA) nucleotides ;
4 DNA polymerase, plus example of role ; e.g. adds complementary nucleotides to exposed strand
forms phosphodiester bonds (between adjacent nucleotides)
proofreading / checking for errors / checking for mismatches
5 leading strand synthesised continuously / AW ;
6 lagging strand synthesised in (Okazaki) fragments ;
7 ligase connects (lagging strand), fragments / nucleotides, (with phosphodiester bonds) ;
8 semi-conservative replication / AW ;
e.g. both new double helices have one, parental / conserved, strand and one newly synthesised strand
Transcription
Transcription
Occurs in the nucleus
DNA unwinds to form two strands (template and non-template)
Only one strand acts as the template (the template strand)
Free-activated RNA nucleotides line up with their complementary base and form H-bonds
RNA polymerase catalyses the synthesis of phosphodiester bonds to form a sugar-phosphate backbone
Hydrogen bonds between the DNA and mRNA strands are then broken
DNA is reformed
mRNA strand then leaves the nucleus through the nuclear pores
