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
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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
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3
Q

how long can it take to replicate bacterial genome

A

15 mins

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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
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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
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6
Q

intracellular organisms

A

have to live inside another organism bc its genome is so small

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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
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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
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