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MRS.SRIDEVI

Cell Biology

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Cell Biology –Today’s Topics

• Size• Shape• ComponentsChromosome

• Basic techniques

• Steps Involve

Genetic Engineering

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Introduction

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Chromosome -SizeRanges from

0.25 μm (fungi) – 30 μm (Trillium)

Chromosomes in plants larger than in animals

Chromosomes in monocots larger

than dicotyledons

Largest chromosomes:Lampbrush chromosomes in Oocytes of vertebratesPolytene chromosomes (salivary gland cells of

dipteran insects)

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Chromosome -Shape

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Chromosome -NumberSpecies Botanical Name Diploid Number

of Chromosomesrice Oryza sativa 24maize Zea mays 20great millet Sorghum vulgare 20peanut, ground nut Arachis hypogaea 40

soybean Glycine max 40mung bean, green gram Phaseolus aureus 22

upland cotton Gossypium hirsutum 52

mango Mangifera indica 40

cassava Manihot utilissima 36

sugarcane Saccharum officinarum 80

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Chromosome -Components

Satellite

Primary Constriction

Secondary Constriction

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Chromosome -Types

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Polytene ChromosomesDiscovery

• C.G. Balbiani (1881) in the

salivary glands of

Drosophila.

Characteristic features

• Inter bands, along the

length of the chromosome.

• Balbiani ring or

chromosomal puff.

Other Name

• Salivary gland

chromosomes, as they

occur in the salivary glands.

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Special Types: Lampbrush ChromosomesDiscovery•Observation by Flemming (1882)•Description by Ruckert (1892)

Occurrence•At the diplotene stage of meiotic prophase in oocytes of Salamandor•In giant nucleus of theunicellular alga Acetabularia.

Structure•Lateral loops of DNA extend as a result of intense RNA synthesis.

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Genetic Engineering

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GE - Applications

Pharmaceutical

Industry• Production of proteins, enzymes, hormones, antibiotics

Agriculture• Formation

of pest resistant, disease resistant plants, edible vaccines

Medicine• Correcting inborn genetic defects. e.g., production of human growth hormone

Forensic Science

• Determine criminals through DNA finger printing etc.

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