Post on 18-Dec-2015
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Cell Biology –Today’s Topics
• Size
• Shape
• Components
Chromosome
• Basic techniques
• Steps Involve
Genetic
Engineering
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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 -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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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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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.