Cell Biology Mrs.Sridevi

Cell Biology –Today’s Topics Chromosome Size Shape Components Genetic Engineering Basic techniques Steps Involve

Introduction

Chromosome -Size Ranges from 0.25 μm (fungi) – 30 μm (Trillium) Chromosomes in plants larger than in animals Chromosomes in monocots larger than dicotyledons Polytene chromosomes (salivary gland cells of dipteran insects) Lampbrush chromosomes in Oocytes of vertebrates Largest chromosomes:

Chromosome -Shape

Diploid Number of Chromosomes Chromosome -Number Species Botanical Name Diploid Number of Chromosomes rice Oryza sativa 24 maize Zea mays 20 great millet Sorghum vulgare peanut, ground nut Arachis hypogaea 40 soybean Glycine max mung bean, green gram Phaseolus aureus 22 upland cotton Gossypium hirsutum 52 mango Mangifera indica cassava Manihot utilissima 36 sugarcane Saccharum officinarum 80

Chromosome -Components Secondary Constriction Satellite Primary Constriction

Chromosome -Types

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.

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 the unicellular alga Acetabularia. Structure Lateral loops of DNA extend as a result of intense RNA synthesis.

Genetic Engineering Selection, Isolation and Cutting of desired gene Integration of desired gene into vector, mostly plasmid DNA of bacterium. Result: Formation of recombinant DNA or hybrid DNA. Introduction into the bacterial host

Pharmaceutical Industry 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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