module 2. cels

• Chargaffs discovery?

  1. A-T, G-C
  2. the composition of DNA varies between species
• how many hydrogen bonds are between A and T nucleotides?

  2
• How many hydrogen bonds are between G and C nucleotides?

  3
• what nucleotides make up DNA and RNA respectively?

  DNA= A, T, G, C

  RNA= A, U, G, C
• what is the direction of DNA synthesis?

  5' ---> 3'
• what direction are the parental template strands run in?

  3'--->5'
• how many pairs of chromosomes are in humans?

  23
• which nucleotide pairing is rich in regions where replication originates?

  A-T
• What 6 things are needed to make a DNA copy?

  addition of nucleotides, starting point for nucleotide addition, unwinding of the DNA helicase, release of tension in DNA helicase, prevention of unwound DNA reforming, joining of newly synthesised fragments via lagging and leading strands.
• how is the leading strand synthesised?

  continuously in the 5' to 3' direction
• how is the lagging strand synthesised?

  discontinuously in the 5'3 direction as Ozazaki fragments
• what is the role of primase?

  enzyme that make an RNA primer - starting point for DNA polymerisation
• what is the role of DNA Pol |||?

  enzyme that synthesised a new DNA strand by adding complementary nucleotides to the parental template strands
• what is the role of DNA Pol |?

  removes RNA primers and fills the gam with DNA nucleotides.
• what is the role of DNA ligase?

  joins the newly synthesised ozaki fragments together as well as the newly synthesised fragments from the multiple replication bubbles including lagging strands.
• what bonds are created between the Ozazaki fragments?

  phosphodietster
• what is the role of topoisomerase?

  nicks and rejoins DNA strands.
• what is the role of single stranded DNA binding proteins?

  prevents unwound DNA from reforming and protects against degradation.
• when can DNA errors be repaired?


  during replication via exonuclease, and after replication via endonuclease
• how are DNA errors during dna replication fixed?

  exonuclease DNA pol ||| removes incorrect bases
• how are DNA errors after replication fixed?

  incorrect base including bases close by are removed as a segment via an endonuclease.
• PCR?


  vitro/artificial method of making multiple DNA copies
• What components are required for PCR (vitro)?

  DNA template, primers, DNA Pol, free nucleotides.
• difference between vivo and vitro?

  vivo is in cells, and vitro is in lab
• genetic diversity made through what two processes in meiosis?

  Independent assortment and crossing over
• Aneuploidy?


  abnormal number of a particular chromosome
• non disjunction?


  failure of chromosomes to separate properly during anaphase 1 resulting in abnormal meiosis 2 result.
• klinefelter syndrome?


  xxy chromososmes instead of xx or xy
• x inactivation?


  one of the x's from the maternal chromosome is inactivated.