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DNA: Structure and Function The DNA Revolution 1940s-1960s Griffith & Avery—DNA transformed pneumococcus bacteria. Encouraged the study of prokaryotic chromosomes. Hershey and Chase—Bacteriophage experiment. DNA from viruses is injected to host bacteria cells. Griffith and Avery

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Presentation Transcript
the dna revolution
The DNA Revolution
  • 1940s-1960s
  • Griffith & Avery—DNA transformed pneumococcus bacteria.
  • Encouraged the study of prokaryotic chromosomes.
  • Hershey and Chase—Bacteriophage experiment. DNA from viruses is injected to host bacteria cells.
the search for the structure of the dna molecule
The Search for the Structure of the DNA Molecule
  • 1951—Rosalind Franklin—X-ray crystallography
  • Chargaff—Chargaff’s rules. Ratio of nitrogenous bases in DNA. Complimentary bases.
  • Watson & Crick--1953
watson crick model of dna
Nucleotides

Sugar—Deoxyribose

Phosphate Group

Nitrogenous Bases

Adenine & Thymine are complementary.

Cytosine and Guanine are complimentary.

Purines—Adenine & Guanine

Pyrimidines—Cytosine & Thymine

5’ End—Phosphate side

3’ End—Other side

Watson & Crick Model of DNA
watson crick model
DNA is composed of 2 chains of nucleotides that form a double helix shape.

The two strands are antiparallel.

The backbone of the DNA molecule is composed of alternating phosphate groups and sugars.

The complimentary nitrogenous bases form hydrogen bonds between the strands.

A is complimentary to T and G is complimentary to C.

Watson & Crick Model
slide15
DNA
  • Functions
  • 1. Storage of genetic information
  • 2. Self-duplication & inheritance.
  • 3. Expression of the genetic message.
  • DNA’s major function is to code for proteins.
  • Information is encoded in the order of the nitrogenous bases.
chromosomes
Prokaryotic

Circular

Very small

1 chromosome per cell

Some enzymes and proteins are associated with the DNA.

Not housed in a nucleus.

Eukaryotic

Linear

Fairly long

Several chromosomes per cell.

Histone proteins---”spools”. Same in all eukaryotes

Housed in a nucleus.

Nucleosome—2 loops of DNA wrapped around 8 histone proteins.

Unity theme.

Chromosomes
central dogma of genetics
DNA

mRNA

Proteins

Traits

Replication

Unzip

Template

Floating nucleotides

Template

Sense strand

Semiconservative Replication

DNA Polymerase

Proofreading functions

5’ to 3’ only

Replication fork

Discontinuous assembly

Okazaki fragments

Central Dogma of Genetics
slide24
RNA
  • 3 types—mRNA, tRNA, rRNA
  • Ribose
  • Uracil replaces Thymine
  • Single stranded helix
transcription
Transcription
  • RNA polymerase
  • Messenger RNA
  • mRNA
  • Unzipping of DNA helix.
  • Sense strand or template strand
  • Codons
  • Genetic code
translation
Ribosomes

rRNA

Large and small subunits

Codons

Initiator or start codon

Methionine (AUG)

Stop codons

tRNA

Initiation

Chain Elongation

Peptide bonds

Chain termination

Polysome

Translation