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 13,600 1 gene per 9,000 bases 8 (fruit fly) Arabidopsis thaliana 125 million bases 25,500 1 gene per 4000 bases 5 (plant) Zea mays (corn) 5000 million bases ~25,000 1 gene per 200,000 bases 10 Oryza sativa (rice) 565 ~25,000 1 gene per bases 12 Caenorhabditis elegans 97 million bases 19,100 1 gene per 5000 bases 6 (roundworm) Saccharomyces cerevisiae 12 million bases gene per 2000 bases 16 (yeast) Escherichia coli 4.7 million bases gene per 1400 bases 1 (bacteria) H. influenzae (bacteria) 1.8 million bases gene per 1000 bases 1
Chromosome = Protein + DNA
Indirect Evidence of DNA as genetic material
Bacteria transforming factor- Griffiths 1928
Hershey and Chase Expt 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 – 2 antiparallel chains
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
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
Translation
Translation- animated
Gene regulation _Operon 1
Gene regulation _Operon 2
Gene regulation _Operon 3
Mutation
Mutation_altered genetic info
Types of mutation
Causes of mutation Spontaneous Chemical mutagens Physical agents
Results of mutation Extra compound eyes Variations in pigments Both Wings on same side 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
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_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