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IN SITU HYBRIDIZATION (ISH)

IN SITU HYBRIDIZATION (ISH) Introduction In situ hybridization (ISH) is a molecular biology and cytogenetic technique used to detect and localize specific DNA or RNA sequences within intact cells, tissues, or chromosomes. The term in situ means “in the original place”, indicating that the target nucleic acid is identified without extracting it from the cell, thereby preserving cellular and tissue morphology. ISH is widely used in gene mapping, gene expression analysis, medical diagnosis, and developmental biology. Principle of In Situ Hybridization The principle of ISH is based on complementary base pairing between a single-stranded, labeled nucleic acid probe and its complementary target DNA or RNA sequence present in fixed cells or tissues. The sample is fixed on a slide. Target nucleic acids are denatured to single strands. A labeled probe hybridizes specifically with the target sequence. Excess probe is washed away. The hybridized probe is visualized using appropriate detection sys...

••CLASSIFICATION OF ALGAE - FRITSCH

MODULE -1 PHYCOLOGY CLASSIFICATION OF ALGAE - FRITSCH ❖F.E. Fritsch (1935, 1945) in his book“The Structure and Reproduction of the Algae”proposed a system of classification of algae. He treated algae giving rank of division and divided it into 11 classes. His classification of algae is mainly based upon characters of pigments, flagella and reserve food material. Classification of Fritsch was based on the following criteria o Pigmentation. o Types of flagella o Assimilatory products o Thallus structure o Method of reproduction Fritsch divided algae into the following 11 classes 1. Chlorophyceae 2. Xanthophyceae 3. Chrysophyceae 4. Bacillariophyceae 5. Cryptophyceae 6. Dinophyceae 7. Chloromonadineae 8. Euglenineae 9. Phaeophyceae 10. Rhodophyceae 11. Myxophyce...

Exploitation of Somaclonal and Gametoclonal Variations for Plant Improvement

Exploitation of Somaclonal and Gametoclonal Variations for Plant Improvement 1. Introduction Plant tissue culture often induces genetic and epigenetic variations among regenerated plants. These variations, when stable and heritable, can be exploited as a source of novel traits for crop improvement. Somaclonal variation: Variation arising in plants regenerated from somatic cells cultured in vitro. Gametoclonal variation: Variation arising in plants regenerated from gametic cells (anther, pollen, ovule culture). Both provide additional genetic variability beyond conventional breeding. 2. Somaclonal Variation 2.1 Definition Somaclonal variation refers to genetic variation observed among plants regenerated from somatic tissue cultures, such as callus, suspension cultures, or explants. Term coined by Larkin and Scowcroft (1981). 2.2 Sources of Somaclonal Variation Chromosomal changes Aneuploidy Polyploidy Chromosome rearrangements Gene mutations Point mutations Insertions and deletions...

Mapping of DNA

DNA MAPPING 1. Introduction DNA mapping refers to the process of determining the relative positions of genes or DNA sequences on a chromosome. It provides information about the organization, structure, and distance between genetic markers in a genome. DNA mapping is an essential step toward genome sequencing, gene identification, disease diagnosis, and genetic engineering. DNA maps serve as roadmaps that guide researchers to locate specific genes associated with traits or diseases. 2. Objectives of DNA Mapping To locate genes on chromosomes To determine the order of genes To estimate distances between genes or markers To study genome organization To assist in genome sequencing projects. 3. Principles of DNA Mapping DNA mapping is based on: Recombination frequency Physical distance between DNA fragments Hybridization of complementary DNA Restriction enzyme digestion Use of genetic markers The closer two genes are, the less frequently they recombine during meiosis. 4 . Types of DNA...

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