LECTURE 11 Flashcards
what is the mechanism of DNA replication?
- unwinding of DNA at origin of replication
DnaA helicase binds to oriC locus (high AT region)
DnaB replaces DnaA - topoisomerases (DNA gyrase) release the tension created by helicase unwinding
- single stranded DNA binding proteins keep the two strands separate
- DNA polymerase III replicates the two strands in the 5’ to 3’ direction
at what speed does DNA polymerase III go?
750-1000 base pairs/second
what is the proof reading mechanism
DNA polymerases have a 3’ to 5’ exonuclease activity
how does leading strand synthesis go?
DNA polymerase III synthesizes from 5’ to 3’ continuously
how does lagging strand synthesis go?
what is a gene (cistron)?
nucleotide sequence that codes for an mRNA, tRNA or rRNA
what are the four parts of bacterial genes?
promoter
leader
coding region
trailer
what is the difference between eukaryotic and prokaryotic genes?
prokaryotic: continuous
eukaryotic: interrupted by introns
why are there more codons than amino acids?
genetic code is degenerate
there is more than one codon for most amino acids (up to 6)
which are the amino acids that have only one codon?
tryptophan and methionine
how many sense and non sense codons?
61 sense codons
3 stop codons
why are there not 61 different tRNAs?
wobble (loose pairing) between the codon (mRNA) and anticodon (tRNA) during translation
one tRNA can read more than one codon
how is wobble base pairing made?
the amino group from adenine is made into a carbonyl group by adenine deaminase to make an inosine
the inosine can now bind with cytosine uracil and adenine
