11/ bacterial genetics 1 Flashcards
(8 cards)
1
Q
how is genetic info organised in a bacteria
A
- in a nucleoid
- loops of supercoiled dna, anchored in the middle by histone-like anchoring proteins
- looks like a flower
- supercoiling is relaxed in a nicked strand
2
Q
how is supercoiling achieved
A
- enzymes (topoisomerases) make double stranded break in the circle
- passes another part of DNA through the break
- reseals it
3
Q
how long can it take to replicate bacterial genome
A
15 mins
4
Q
how does dna replication occur in bacteria
A
- oric (origin point) recognised
- replication bubble forms
- semiconservative replication, clockwise and anticlockwise direction
- one strand okazaki fragment - dna pol 5’ to 3’ only
- terminates at termination points
5
Q
what are the termination points for e coli
A
- over 8 arrest sites
- replication forks moving clockwise trapped by terB, C, F, G, J
- anticlockwise forks trapped by terA, D, E, H, I
6
Q
intracellular organisms
A
have to live inside another organism bc its genome is so small
7
Q
difference between pro and euk coding vs non coding genes
A
- only 5% of genes in humans code for proteins, coding regions separated by introns, ancient genes decayed to pseudogenes.
- bacterial chromosome tightly packed w coding genes, few mobile elements, little unused sequence
8
Q
what are operons and regulons in bacteria
A
- operons are multiple genes controlled by same promotor that make a polycistronic message that codes for multiple proteins
- (individual genes make monocistronic mrna)
- genes and operons may form a regulon controlled by a common regulatory protein - dif genes in dif operons cand be simultaneously activated