1.intro and genome composition-1

8/10/2019 1.Intro and Genome Composition-1

1/13

Genetics and Molecular Biology (Basic)- Course Outline

Genome composition

Organization of the genome,Coding and non-coding sequences,

Regulatory elements, repeat sequences, transposons, organelle genomes

Chromosome structure and function

Packaging of DNA into the nucleus, nucleosomes,

Chromosome features-centromeres, telomeres, chromosome segregation

in mitosis and meiosis

DNA replication

DNA polymerases, mechanism of replication,

Replication of damaged DNA, termination


2/13

Mutations

Sources of mutations, types of mutational events,Methods to detect mutations, mutations and disease)

DNA Repair

DNA damage response, Mismatch repair, Base Excision repair,Nucleotide Excision repair, Double strand break repair

DNA Recombination

Recombination models, Recombination proteins, Gene conversion,

Homologous Recombination, DNA recombination and chromosome segregation

Genetics and Molecular Biology (Basic)- Course Outline

Suggested Reading: Genes IX (Benjamin Lewis)

Molecular Biology of the Gene (Watson et al.,)DNA Mutagenesis and Repair (Friedberg)


3/13


4/13

Genome sizes vary considerably between different species

Genome size basepairs

Genes IX (Benjamin Lewis)


5/13

Genome organization and size varies between organisms



6/13

Complex genomes have considerable non-coding DNA


7/13

C value paradox

C value- The total amount of DNA in the haploid genome

- Excess DNA compared to the number of proteins the genome codes for- No correlation between C value and morphological complexity

DNA reassociation analysis (CoT analysis)

- Important approach for studying genome complexity.- Total genomic DNA is first fragmented to a relatively small size

- The DNA is then denatured and allowed to renature by gradual

reductions in temperature. This reveals different 'Cot' values, which are

the product of the DNA concentration in moles per litre (Co) and the

reassociation time in seconds (t),


8/13

DNA reassociation analysis


9/13

Estimate fraction of reassociated DNA

Double stranded DNA has higher affinity for a crystalline form of Calcium Phosphate

Hydroxyapatite. Both ssDNA and dsDNA can be washed off and estimated separately

http://www.learnerstv.com/animation


10/13

DNA from calf reassociated faster than E.coli DNA!

Extent of reassociation is measured by chromatographic techniques and

plotted against Cot

Calf thymus DNA reassociate as different fragment -fast, median and slow,E.coli DNA behaves mostly as slow component.

DNA reassociation analysis for simple versus complex DNA


11/13

Cot1/2value is a measure of the Genome complexity

Co- 12pg, Bacterial DNA- 0.004pg, Mammalian 3pg

3000 copies of the Bacterial DNA compared to only 4 of the mamalian DNA

(750 fold difference) Either increase concentration or time by 750 fold to get

same Cot1/2


12/13

Utility of Cot analysis

Information on unique sequence content (number of genes)

How much of the DNA is repetitive

Phylogenetic relationships among different organisms

Modern methods for genome complexity analysis


13/13

Highly repetitive, moderately repetitive and Non-

repetitive DNA comprise the Eukaryotic genome

25%

30%

45%


1.intro and genome composition-1

Documents