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 23000 bases 12

Caenorhabditis elegans 97 million bases 19,100 1 gene per 5000 bases 6(roundworm)

Saccharomyces cerevisiae 12 million bases 6300 1 gene per 2000 bases 16(yeast)

Escherichia coli 4.7 million bases 3200 1 gene per 1400 bases 1(bacteria)

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 factor- Griffiths 1928

Hershey and Chase Expt. 1952Viral 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 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

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