Chapter 14: DNA stuffs

MATES Biotechnology, MATES 2024

how are nucleotides built

attach together in a 3’ to 5’

structure of a nucleotide

1. five-carbon sugar

2. phosphate group

3. nitrogen base (purine/pyrimidine)

who were watson and crick?

• developed the current model of DNA based off of past experiments

• learned from Franklin’s double helix discovery

bonding across DNA strands

• H-bonds hold the two strands together

• phosphodiester bonds bind nucleotides together

semiconservative method

each strand is split then duplicated to make 2 new DNA moleules

polymerase function

creates RNA or DNA molecules

• RNA polymerase

  • I - rRNA

  • II - mRNA

  • III - tRNA

• DNA polymerase

  • I - rids RNA primer and double checks DNA strands

  • III - synthesizes DNA in the 5’ to 3’ direction, starts from a primer

primase function

synthesizes RNA primers

gyrase function

prevents supercoiling of DNA

leading vs. lagging strands

• leading strand: continuous synthesis, only one primer needed; building in 5’ to 3’

• lagging strand: strand going in the opposite direction (3’to 5’), synthesis has to come back and create strands → multiple separate primers needed

  • okazaki fragments

okazaki fragment

• incomplete DNA fragments from lagging strands of DNA

• joined together by ligase (glue)