DNA as Genetic Information

• Avery 1944
• Utilised fractionation techniques to purify DNA and transformation was unaffected by protease/RNAse
• DNA was destroyed by DNAse and the mouse stayed alive, suggesting that DNA was the genetic material

• Small and simple (2um)
• 70s ribosomes
• Non-membrane bound DNA
• Plasmids - small circular DNA

Missense mutation - change in base pair results in codon for a different amino acid

Nonsense mutation - change in base pair results in a protein chain-terminating codon

Insertion mutation - adding extra base pairs resulting in change in base number

Deletion mutation - removing sections of DNA

Substitution mutation - exchanges one base for another

Duplication mutation - a piece of DNA abnormally copied 1 or more times

Frameshift mutation - when insertion/deletion alters the gene so codons are changed

Repeat expansion mutation - increases the amount of times that a codon is repeated

Griffth 1928

• Smooth Pneumococcus bacteria is resistant to mouse immune system
• Rough Pneumococcus bacteria lacks the resistant coat
• Indicated information was passed on from dead type to live type = transforming principle

• Nucleus containing DNA
• Membrane-bound organelles
• 20um diameter (larger)
• 80s ribosomes
• Chromosomes hold DNA

Downs Syndrome - 3 copies of chromosomes 21 (often from older mothers)

Turner Syndrome - woman with 1 X chromosome (monosomy) = infertile, short

Klinefeller Syndrome - man with 1 Y and 2 X chromosomes (trisomy) 

Non-disjunction - failure of homologous chromosomes or sister chromatids to separate during gamete formation

Philadelphia Chromosome - translocation in bone marrow causes permenant switch on = cancer

Cystic Fibrosis - recessive mutation causing a deletion in CFTR channel gene = sticky mucus

Sickle-cell Disease - mutation from A to T in beta haemoglobin chain = anemia, pain, infection

Chromosome - a protein and DNA complex containing all/part of genome

• HUMANS HAVE 46 - 23 PAIRS

Diploid cells - cell with 2 equivalent sets of chromosomes e.g. epithelial

Haploid cells - cell with one set of unique chromosomes e.g. gametes

Homologous chromosomes - pair of chromosomes with same genes (maybe different alleles)

Chromatin - the DNA/protein complex folded into a compact structure

Karyotype - number and visual appearance of full set of chromosomes

Hershy and Chase 1952

• 1 bacteriophage labelled with radioactive sulphur in protein coat (DNA has no sulphur)
• 1 bacteriophage labelled with radioactive phosphorous - incorperated into DNA
• Phage DNA entered bacterial cells but not proteins - DNA genetic material

Dark parts (less):

• AT-rich
• More condensed
• Less transcriptionally active

= HETEROCHROMATIN

Light parts (more)

• GC-rich
• Less condensed
• More transcriptionally active

= EUCHROMATIN

Miescher 1869:

• Protein function study of pus
• Cell cytoplasm from white blood cells
• Add acid = white precipitate
• Rich in phosphorous but no sulphur (not protein)
• Nuclein now called DNA