Summary: 2021 Genen En Cellen

Read the summary and the most important questions on 2021 Genen en Cellen

• 5 Hoorcollege 5

• 5.1 Deel 1

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• Functie DNA helicase?

  Zorgt ervoor dat de twee DNA strengen van elkaar scheiden
  
  Travels along one DNA strand in the 5' tot 3' direction and separates the DNA strand

• DNA topoisomerase functie?

  --> zorgt ervoor dat de spanning op de DNA streng niet te hoog wordt, zodat er niet te veel kracht op komt voor de replicatie. 
  Travels slisghtly ahead of the replictaion fork and alleviates coiling caused by the action of helicase

• Single-strand binding proteins?

  Coat the DNA strands to prevent them fro re-forming a double helix and protect the DNA

• 5.2 Deel 2

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• Wat doet DNA polymerase?

  Synthetiseert Covalente binding tussen nucleotide 
  - Tri-phosphate nucleotiden, twee phosphaat eraf --> energie
  
  bouwt de complementaire nucleotides  op basis van de template strand

• What happends if the DNA strand separates at an origin of replication, creating 2 replication forks?

  1) Primers are needed to initiate DNA synthesis. The synthesis of the leading strand begins in the direction of the replication fork. On the lagging strand, an Okazaki fragment are made in the opposite direction. 
  
  2) The leading strand elongates, and a second Okazaki fragment is made.

• Verschillen en gelijkenissen tussen leading strand en Lagging strand

  LEADING:
  - DNA synthesized in as one long molecule 
  -DNA primase makes a single RNA primer 
  - 5' --> 3' direction
  
  LAGGING:
  - DNA synthesized 5' --> 3' a Okazaki fragments 
  - Okazaki fragments consist of RNA primers plus DNA
  
  BOTH:
  - RNA primers are removed by DNA polymerase and replaced with DNA 
  - DNA ligase joins adjacent DNA fragments

• Verschil DNA polymerase en DNA ligase?

  DNA polymerase kan alleen maar nieuwe nucleotides inbouwen, en DNA ligase kan  ook de nieuwe covalente binding aanleggen. (kan 2 gesynthetisserde moleculen met elkaar verbinden dmv covalente bindingen.

• 3 manier of DNA compaction:

  1) DNA wrapping in Nucleosome 
  - het DNA wordt letterlijk  om histonen van nucleosomen heen gevouwen en wordt bij elkaar gehouden door weer een ander histon 
  
  2) 30-nm fiber 
  - Asymmetrich, 3-D zigzag van nucleosomes
  
  3) Radical loop domains
  - Interaction between 30 nm fibers and nuclear matrix.
  - elk chromosoom heeft eigen plek in nucleus

• 7 Connect toets Hoofdstuk 14

•  What is the MOST important factor determining the control of gene expression?

  The level of transcription (when a gene is transcribes to mRNA)

• What is the most important reason a cell would have translational control over the regulation of gene expression?

  At the translational level, protein synthesis can be turned on and off quickly to respond to the needs of the cell