Cell Biology Lecture 14: DNA Heredity, Structure and Replication

Griffith Experiment Condition #1

Live S strain live S strain from blood mouse dies

Griffith Experiment Condition #2

Mouse lives, few live R strain from blood

Griffith Experiment Condition #3

Heat killed s strain, mouse lives no live cells

Griffith Experiment Condition #4

live R plus heat killed S strian, mouse dies, live s strain from blood 

Avery Macleod and McCarthy Experiment

heat killed s strain and live R plus one of the enzymes 

Conclusion of Avery Macleod and McCarthy Experiment

DNA is the genetic material

What is DNA

polymer made up of A T G and C

Chargaff Rules

Base pairing rules

Fraklin discoveries on DNA

DNA is a double helix, 10 nucleotides per turn

Watson and Crick discoveries on DNA

strands are antiparallel, base pairs based on Hbonding, General mechanism for replication, parent strands acting as template for daughter strands. 

What does adding an acetyl group do

loosen DNA from histone

What does adding methyl group do

condenses DNA

Heterochromatin

Condensed Chromosomes

Euchromatin

Uncondensed chromatin

Semi-conservative

new double helix contains are 100% parent strand one 100% daughter

Conservative

New double helices are either exclusively parent DNA or exclusively daughter

Dispersive

new double helices are a hybrid mosaic of parent and daughter

Messelson-Stahl experiment

E coli replicated for 24 hours in heavy nitrogen 15. All DNA expected contain N15. After 24 hours transfer to light N14 allow one round replication. This results in one intermediate band 2 rounds replication in 14N one intermediate one light band

2 important ideas for mechanism for replication

Base pairing as process for the parents serving as a template, DNA syntehsis is always 5-3

Helicase

separates parent template strands

Single stranded biniing protein

bind to SS DNA prevent templates from base pairing with each other 

DNA Polymerase

enzyme syntehsizes new DNA

Leading strand

continous syntehsis

Lagging strand

discontinous syntehsis

Primase

RNA polymerase that makes short RNA primers

DNA Polymerase III

syntehsize okazakifragments

DNA Polymerase I

remove RNA primer replace it with DNA

DNA Ligase

Connects okazaki fragements together 

Telomeres

Noncoding nucleotide repeats that are added to the end of the lagging strand and its templae

Mismatch 

Endocuclease, cut from inside not end. Cut out whole sequence, but DNA polyermase repairs 

Excision

removes and replaces damaged DNA segments

Nonhomologous end Jointing

Nucleases digest bases around the site of damage, ligases connect the strands, loss DNA

Homologous recombination

No loss of DNA