Gene regulation Flashcards
(69 cards)
Vad är det för skillnad mellan kromosomerna hos en bakterie och en eukaryot cell?
Prokaryote:
chromosome in cytosol, circular chromosome, no intrones/exones, compact.
Eukaryotes: linear chromosomes in nucleus. Exones/intrones, splicing of RNA, låg andel proteinkodande DNA.
Vilken funktion har telomererna?
The ends of the chromosomes. Telomerer som en buffert som kan forstörras litegran
Varför tror du det finns det så många Ori hos eukaryoter
Ori = replication origin. Där replikation börjar. Cellen kan använde på fler ställen samtidigt, på så sätt snabbare replikerar genomet.
Beskriv hur DNAt är packat i en eukaryot kromosom.
lindad två varv DNA linker DNA histon complex loopas ihop kromatinfiber loopade kromatin
Kromosom innehåller proteiner, histoner (50% of the mass), DNA+proteiner = kromatin. Nukleosom är kromatinets minsta enhet består av histon med ca två varv DNA helix (147 bp) och DNA linker (80 bp)
packas i fler nivå.
centromer håller ihop de två kromosom
Hur kan cellen ändra kromatinets packningsgrad?
På två sätt. I flytta histon complex. II. Cellen kan göra modifieringar så det inte bindar lika hårt.
What does DNA-polymerase do?
DNA polymerase follow helicase synthesising new DNA.
The direction is always 5’ to 3’ very important! On 5’ prime end is the phosphate group. On 3’ prime end an OH group. Make and synthesise them 5’ to 3’.
What does the protein helicase do in DNA replication?
Helicase unwinds the two DNA strands
Is DNA antiparallel?
Yes
How is the lagging strand of DNA synthesised during DNA replication?
5’ to 3’ just as the leading strand. Since helicase is moving in the opposite direction for the lagging strand, it has to make Okazaki fragments that will later be “glued” together
Is DNA replication bidirectional?
Yes
What are the three stages of DNA replication?
Initiation, elongation and termination
What makes an ORI the origin of initiation?
A-T rich area. Two hydrogen bonds. Its easier to break two hydrogen bonds than three (C-G). Better suited for separation because of only two hydrogen bonds, requires less energy.
What is the purpose of the single stranded binding protein during DNA replication?
Protein that helps to protect the bases, its purpose is to prevent parental strands from reannealing. Protect from nucleases (that would want to cut).
What is helicase?
Enzyme that unwinds DNA at both replication forks.
Helicase requires a ton of ATP. Bunches up DNA and creates supercoils
How are the supercoils fixed during DNA replication?
Topoisomerases (shaped like a T, different types 1,2 and 4). It can cut the DNA strand for the DNA to unwind and unravel. That part of topoismerase arm is called nuclease domain. The other arm called ligase domain to restitch the area back together.
What does primase do during DNA replication?
Enzyme primase makes RNA primers. Reads DNA strand 3’ to 5’. Synthesises RNA primers 5’ to 3’, 5-10 nucleotides. On 3’ end we have OH.
What does DNA polymerase III do?
DNA polymerase III will make DNA but needs RNA primers, needs the 3’ OH of RNA primer.
DNA polymerase III has another function than elongation from RNA primers, what is that?
Proof reading. Reads 3’ to 5’
3’ to 5’ exonuclease activity to cut out and put correct bases.
What does DNA polymerase I do?
It removes primers 5’ to 3’ with exonuclease activity. Reads 3’ to 5’ and synthesises 5’ to 3’.
What is the difference between polymerase I and III?
That I can remove RNA primers using 5’ to 3’ exonuclease activity.
What does the enzyme ligase do during DNA replication?
It fuses DNA ends together from Okazaki fragments and from where RNA primers were
What are the centres and ends of chromosomes called?
Centromeres and telomeres.
What function does telomeres have?
They don’t code for anything so they act as a buffer. They shorten over time. Prevent gene loss.
What is the Hayflick limit?
is the max amount of time that DNA can replicate before it starts to involve genes. The last RNA primers, there is no 3’ end that DNA polymerase can add bases to. This is why it shortens.
