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Nuclear DNA Condenses during the cell division and appears as ‘colored bodies’ (with stains); the Chromo+somes.

Chromosomes were discovered by Karl von Nageli in 1842, later the term ‘Colored bodies were coined by HW Waldeyer (1888). However, the modern understanding came into light years later..

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Mendel's to Chromosome theory (or Sutton-Boveri Theory)

chromosomes, which are seen during cell division pass from one generation to the next, forms the basis for genetic inheritance

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Introduction cont…

Mendelian inheritance to chromosomes to Genes

Thomas Hunt Morgan demonstrated that genes are carried on chromosomes and are the mechanical basis of heredity. He was awarded the 1933 Nobel Prize.

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Exposed chromatin is ‘Euchromatin’ allows gene expression (transcription)

Compacted chromatin (unexposed) in non dividing cell is heterochromatin

Compacted chromatin in dividing cells are chromosomes

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Chromatin & Chromosome

Chromatin & Chromosome

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The Chromatin versus Chromosome

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The structural unit of chromatin

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Core histone consists of

Pair of H2A, H2B, H3 & H4

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110 Å

2400Å

Copy right US national library of Medicine

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Chromosome is an organized DNA and protein found in the cell.

Chromosome is a single piece of coiled DNA containing many genes.

Chromosomes are structures ready to pass genetic information to next generation: the heredity

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Objectives To study the methods of

chromosome analysis i.e. Karyotyping and other methods.

Chromosomal abnormalities (2nd lecture)

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Karyotyping Fluorescent In-situ Hybridization (FISH) Comparative Genomic Hybridization

(CGH)

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A method of analyzing chromosomes Any human cell that undergoing cell division

can be used to analyze human chromosomes Method:

1. Add a mitotic stimulant to cells i.e. Phytphaemagglutinine

2. Culture for 3 days3. Add colchicine to the cell culture to arrest the

cell at metaphase4. Burst the cells with hypotonic saline to release

chromosomes5. Stain the chromosomes (Giemsa)6. Photograph the stained chromosomes7. Arrange the chromosomes pictures

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Method in brief

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Complementary Fluorescent probe

A A T

T T A

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FISH image of chromosomes with a probe that 'paints' chromosome 10. Note the extra chromosome 10 material on chromosome 2, which is abnormal.

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Identifies abnormal areas in chromosomes (i.e. in tumor cells)

No need to use the dividing cells

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The next lecture

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