DNA Function & Replication

DNA Structure

Composition of nucleotides by Chargaff: equal A&T, equal G&C

Rosalind Franklin

Used X-ray crystallography to identify DNA structure components

Erwin Chargaff

Discovered equal ratios of A&T, G&C in DNA nucleotides

Watson-Crick Base-Pairing

A binds with T, G binds with C in DNA strands

DNA Replication Purpose

To make more cells with their own DNA for growth & repair

Semiconservative Model

New DNA has one old parental strand, one new daughter strand

DNA Replication Speed

E. coli replicates 4.6M DNA bp in ~1h, human 6B bp in few hrs

Origin of Replication

Start point for DNA replication to decrease replication time

Leading Strand

Continuously synthesized DNA strand towards the forking point

Lagging Strand

DNA strand synthesized away from fork in Okazaki fragments

DNA Polymerase

Adds nucleotides in 5' to 3' direction during DNA replication

Topoisomerase

Unwinds DNA strands during DNA replication process

Helicase

Separates double-stranded DNA helix during DNA replication

DNA Ligase

Links DNA fragments to form single strands in DNA replication

Proofreading in DNA Replication

Ensures proper base pairing and repairs DNA damage

Complementary Base Pairs

Purine on one strand binds with pyrimidine on the other

DNA Replication Components

Include template strand, nucleotides, and various enzymes

DNA Replication Overview

Parental DNA strands separate, new strand assembly with nucleotides

DNA Replication Specifics

Proteins attach to DNA at origin, polymerase adds nucleotides

DNA Replication Bubbles

Formed when DNA is opened up during replication process

DNA Replication Enzymes

Include topoisomerase, helicase, DNA polymerase, and ligase

DNA Replication Direction

Opposite strands replicate to speed up DNA replication process

DNA Replication Advantages

Ensures genetic information consistency in multicellular organisms

DNA Replication Consistency

Half of the DNA is conserved from the parental molecule

DNA Replication Proofreading

Checks for proper base addition and repairs DNA damage

DNA Replication Daughter Strands

End result of the process, two identical daughter DNA molecules