The chemical Basis of Inheritance
Chromatin / Chromosomes
Organism
estimated size
estimated gene number average gene density chromosome #
Homo sapiens (human)
2900 million bases
~30,000
1 gene per 100,000 bases
46
Rattus norvegicus (rat)
2,750 million bases
~30,000
1 gene per 100,000 bases
42
Mus musculus (mouse)
2500 million bases
~30,000
1 gene per 100,000 bases
40
Drosophila melanogaster 180 million bases
(fruit fly)
13,600
1 gene per 9,000 bases
8
Arabidopsis thaliana
(plant)
125 million bases
25,500
1 gene per 4000 bases
5
Zea mays (corn)
5000 million bases
Oryza sativa (rice)
565
Caenorhabditis elegans
(roundworm)
97 million bases
Saccharomyces cerevisiae 12 million bases
(yeast)
~25,000
1 gene per 200,000 bases
10
1 gene per 23000 bases
12
19,100
1 gene per 5000 bases
6
6300
1 gene per 2000 bases
16
~25,000
Escherichia coli
(bacteria)
4.7 million bases
3200
1 gene per 1400 bases
1
H. influenzae (bacteria)
1.8 million bases
1700
1 gene per 1000 bases
1
Chromosome = Protein + DNA
Indirect Evidence of DNA as
genetic material
Bacteria transforming factorGriffiths 1928
Hershey and Chase Expt. 1952
Viral Life Cycle I
Viral Life cycle II attachment, penetration,
replication, assembly, lysis
Hershey and Chase – Protein
coat labeled virus
Hershey and Chase – DNA
labeled virus
32P - Radioactivity appear in
progeny
35S – No Radioactivity in progeny
Hershey and Chase
Watson and Click Model 1953
DNA – A Double Helix
DNA – Sugar phosphate
backbone
DNA – Polynucleotide chain
DNA – A Nucleotide unit
DNA – Sugar / pentose
DNA – Organic Bases
Purines
Pyrimidine
DNA – Base pairing
DNA – Base pairing
DNA – 2 antiparallel chains
DNA
vs
RNA
DNA vs RNA
DNA - The molecule of life
Each cell:
•46 chromosomes
•2 meters of DNA
•3 billion DNA
bases
•Approximately
30,000 genes
From DNA to Human
DNA replication – overall process
DNA replication
Three models of DNA replication
Evidence for a Semi-conservative
model
Semi-conservative replication
DNA replication
The triplet code I
The triplet code II- start
The triplet code III- termination
The triplet code IV- degenerate
The triplet code IV- Non-overlapping
The triplet code V – no punctuation
Breaking the code
Breaking the code
Central Dogma
Transcription
Transcription- animated
Transcription- coding strand
Replication - transcription translation
t-RNA
t-RNA binding sites
Aminoacyl-tRNA complex
Ribosome – Pro- and Eukaryotic
Ribosome- P and A sites
Ribosome- P and A sites
Translation
Translation- animated
Gene regulation _Operon 1
Gene regulation _Operon 2
Gene regulation _Operon 3
Mutation
Mutation
Mutation_altered genetic info
Types of mutation
Causes of mutation
•Spontaneous
•Chemical mutagens
•Physical agents
Results of mutation
Extra compound eyes
Both Wings on same side
Variations in pigments
Sickled cell anaemia
Somatic vs Germinal mutation
Early vs Late somatic mutation
Karyotype
To obtain a karyotype
Down syndrome_aneuploidy
Down syndrome
Eye-folds
Frequency of Down’s syndrome
against mother’s age
Kleinfelter syndrome
Kleinfelter syndrome
Chromosome Mutation-non
disjunction I
Chromosome Mutation-non
disjunction II
XYY
XY vs XYY
XO
XO _Turner syndrome
Euploidy_Autopolyploidy
Autopolyploidy_seedless fruit
How to make seedless fruits?
The resulting 3n zygote develops into a 3n embryo inside a
seed. Planting this seed will yield a 3n watermelon plant bearing
3n seedless watermelons.
Hybrid_sterililty
Unpaired chromosomes—results
in abnormal gamtes
Doubling of chromosomes
allowing pairing of chromosomes and
production of normal gametes
Allopolyploidy_principle
Allopolyploidy in cabbage
Allopolyploidy in cabbage
Allopolyploidy_Wheat
Gene-mutation_Sickled cell
anaemia
The amino acid sequences for the normal and
abnormal P chains differ in the substitution of
valine for glutamic acid at one point in the
abnormal polypeptide chains of haemoglobin S
Significance of mutation