chapter 12-13 – dna and how genes work. what is transforming agent? dna or protein? avery, macleod...
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Chapter 12-13 –DNA and How Genes Work
• What is transforming agent? DNA or protein?
Avery, MacLeod and McCarty
Avery, MacLeod and McCarty
• DNA carries the heritable information
Avery, MacLeod and McCarty conclusion
1944
Hershey and Chase
Martha Cowles Chase
Alfred Day Hershey
Hershey and Chase
Bacteriophage: viruses that infect bacterial cells
Hershey and Chase
• Genetic material in virus was DNA• DNA is agent of heredity
Hershey and Chase conclusion
INDEPENDENT FUNCTIONS OF VIRAL PROTEIN AND NUCLEICACID IN GROWTH OF BACTERIOPHAGE*
B~ A. D. HERSHEY AND MARTHA CHASE(From the Department of Genetics, Carnegie Institution of Washington, Cold Spring
Harbor, Long Island)(Received for publication, April 9, 1952)
The work of Doermaml (1948), Doermann and Dissosway (1949), and Anderson and Doermann (1952) has shown that bacteriophages T2, T3, and T4 multiply in the bacterial cell in a non-infective form. The same is true of the phage carried by certain lysogenic bacteria (Lwoff and Gutmann, 1950). Little else is known about the vegetative phase of these viruses. The experimentsreported in this paper show that one of the first steps in the growth of T2 is the release from its protein coat of the nucleic acid of the virus particle, after which the bulk of the sulfur-containing protein has no further function.
DNA – just what is it?
Nucleic AcidsMonomers =
nucleotides
Polymer = DNA, RNA
DNANucleotide
(monomer)
4 bases
DNA
“double helix”
DNA
A - TG - C
DNA
“double helix”
A - T G - C
Rosalind Franklin (1920-1958)
X-ray crystalography
Structure of DNA
Watson and Crick
1953
Watson and Crick (1953)
Replication
Expression
DNA
DNA Replication
DNA Replication
DNA Replication
DNA Replication
DNA Replication
DNA Replication
DNA
Information stored in order of the bases
+/- 1200 copies
Central Dogma of Cell Biology
DNA (gene)Protein
GENETICS: TA TUM AND BEADLEGENETIC CONTROL OF BIOCHEMICAL REACTIONS IN NEUROSPORA:
AN "AMINOBENZOICLESS" MUTANT*By E. L. TATUM AND G. W. BEADLE
DEPARTMENT OF BIOLOGY, STANFORD UNIVERSITYCommunicated April 17, 1942
Para-aminobenzoic acid has recently been recognized as a factor required for the growth of a number of micro6rganisms' and as a member of the vitamin B group.2 One of the number of x-ray induced mutants of Neurospora crassa, obtained as described elsewhere,' is characterized by the loss of ability to synthesize p-aminobenzoic acid. This "aminobenzoicless“ mutant is differentiated from normal by a single gene, is unable to grow on unsupplemented synthetic medium, but its growth is indistinguishable from normal when p-aminobenzoic acid is supplied.
Each gene codes for a specific and unique protein
1958 – Nobel Prize
One-Gene/One-Polypeptide Hypothesis
Central dogma of molecular biology
Extracting and using the information
Two Steps:
1. 2.
Extracting and using the information
The information
Extracting and using the information
An intermediate
Extracting and using the information
The product
Translation – constructing a protein
DNA mRNA
proteintranscrip
tion
translatio
n
Transcription
DNA copied into mRNA
mRNAsingle-stranded
U instead of T
Translation – constructing a protein
DNA mRNA
proteintranscrip
tion
translatio
n
Instructions are coded in the order of the bases
20 amino acids
Protein is a polymer of amino acids
Instructions are an ordered list of amino acids in protein
Each ‘word’ in the DNA-RNA vocabulary is 3 ‘letters’ long
One “word”
Each ‘word’ in the DNA-RNA vocabulary is 3 ‘letters’ long
A ‘word’ is called a codon
Triplet Codon: group of 3 bases that specifies an amino acid
The Genetic Code
-Redundant -Not ambiguous-Stop codons-AUG - start-Universal (nearly)
Marshal W. Nirenberg
The Dictionary
Punch tape
Ribosome
mRNAtRNA
tRNA brings in the amino acides
Translation
Translation
Translation
Translation
Translation
Translation
Universal (nearly)
Reading frames
the red dog ate the bug
Reading frames
her edd oga tet heb ug
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