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MRS.SRIDEVI

Cell Biology

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Cell Biology –Today’s Topics

• Size

• Shape

• Components

Chromosome

• 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 Chromosomes

rice Oryza sativa 24

maize Zea mays 20

great millet Sorghum vulgare 20peanut, ground nut Arachis hypogaea 40

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

upland cottonGossypium hirsutum 52

mango Mangifera indica 40

cassavaManihot utilissima 36

sugarcaneSaccharum officinarum 80

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Chromosome -Components

Satellite

Primary Constriction

Secondary Constriction

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Chromosome -Types

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Polytene Chromosomes

Discovery

• 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 Chromosomes

Discovery

•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• Productio

n of

proteins,

enzymes,

hormones

,

antibiotic

s

Agriculture• Formation

of pest

resistant,

disease

resistant

plants,

edible

vaccines

Medicine• Correctin

g inborn

genetic

defects.

e.g.,

productio

n of

human

growth

hormone

Forensic Science

• Determin

e

criminals

through

DNA

finger

printing

etc.

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