16, 17, 18, EPIGENETICS.pdf - HISTONES\/NUCLEOSOMES\/DNA PACKAGING \u25cf DNA packaged with proteins \u25cf Histones stabilize and regulate \u25cf Nucleosomes

16, 17, 18, EPIGENETICS.pdf - HISTONES/NUCLEOSOMES/DNA...

This preview shows page 1 - 3 out of 10 pages.

HISTONES/NUCLEOSOMES/DNA PACKAGING DNA packaged with proteins Histones: stabilize and regulate Nucleosomes: group of histones Heterochromatin (methylated) Chromatin that is not easily accessible DNA was methylated (non polar) Euchromatin (acetylated) Looser for gene accessibility PURINES/PYRIMIDINES Cytosine and Thymine - pyrimidines (one circle) Adenine and Guanine - purines (two circles?) ANTI-PARALLEL NATURE OF DNA 3’ to 5’ strand is happy strand ORIENTATION OF REPLICATION 3’ to 5’ USES OF DIFFERENT DNA POLYMERASES DNA polymerase 3: attaches new complementary nucleotides along sugar-phosphate backbone Energy supplied in nucleotides DNA polymerase 1: removes the primer and adds what it can by adding to a free 3 ALL ENZYMES/PROTEINS USED IN DNA REPLICATION Helicases: unwind DNA and separate the DNA strands Topoisomerases: relieves over-twisting further up replication fork DNA polymerase 3: creates new strand from 5’ to 3’ and needs free OH (3rd carbon) to attach on to Can only add to existing chain (needs a primer) RNA primase: makes RNA primer to allow DNA poly 3 to begin with free OH 3’ DNA polymerase 1: removes primer and adds what it can by adding to a free 3 Ligase: comes in to attach Okazaki fragments together Telomerase: comes in and adds nonsense sequences to keep ends from being continually shortened ssbps - creates replication fork
Image of page 1
CAUSES OF THE LEADING/LAGGING STRAND Leading strand: made continuously as replication fork continues to open as this polymerase is moving 3’ to 5’ and making its new strand 5’ to 3’ (adding onto free 3’) Lagging strand: made in pieces on the 5’ to 3’ strand as another polymerase works “backwards” (away from fork) as replication fork continues to open Creating new strand 3’ to 5’ in pieces OKAZAKI FRAGMENTS The pieces that make up the lagging strand SHORTENING OF TELOMERES Ends of chromosomes Huge lengths of DNA that do not contain genes Will absorb all cuttings so nothing good is cut Junk at end of telomeres, so nothing good gets cut off They continuously shorten USE OF TELOMERASE Comes in and adds nonsense sequence to keep the ends from continually being shortened THYMINE DIMERS Created from uV light Where nuclease cuts out damaged DNA, fills in gap using other strand as template Kink where the thymine are REPAIR MECHANISMS (EXONUCLEASES)
Image of page 2
Image of page 3

You've reached the end of your free preview.

Want to read all 10 pages?

  • Fall '17
  • Cannobio
  • DNA, RNA

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture