9252020 CHROMOSOMES AJITH SOMINANDA DEPARTMENT OF ANATOMY FACULTY

9/25/2020 CHROMOSOMES AJITH SOMINANDA DEPARTMENT OF ANATOMY FACULTY OF MEDICINE PERADENIYA 1

9/25/2020 INTRODUCTION AND HISTORY 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. . 2

9/25/2020 Introduction cont… 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 3

9/25/2020 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. 4

9/25/2020 Chromatin & Chromosome Exposed chromatin is ‘Euchromatin’ allows gene expression (transcription) Compacted chromatin (unexposed) in non dividing cell is heterochromatin Compacted chromatin in dividing cells are chromosomes 5

9/25/2020 Chromatin & Chromosome 6

9/25/2020 The Chromatin versus Chromosome 7

9/25/2020 NUCLEOSOME The structural unit of chromatin 8

9/25/2020 NUCLEOSOME CONT. . Core histone consists of Pair of H 2 A, H 2 B, H 3 & H 4 9

9/25/2020 CHROMOSOME IS A SINGLE PIECE OF DNA 2400Å 110 Å 10

9/25/2020 Copy right US national library of Medicine 11

9/25/2020 SO WHAT IS A CHROMOSOME 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 12

9/25/2020 MORPHOLOGY & CLASSIFICATION OF CHROMOSOME 13

STUDY OF CHROMOSOME : THE CYTOGENETICS 9/25/2020 Objectives To study the methods of chromosome analysis i. e. Karyotyping and other methods. Chromosomal abnormalities (2 nd lecture) 14

9/25/2020 METHODS OF CHROMOSOME ANALYSIS Karyotyping Fluorescent In-situ Hybridization (FISH) Comparative Genomic Hybridization (CGH) 15

9/25/2020 KARYOTYPING A method of analyzing chromosomes Any human cell that undergoing cell division can be used to analyze human chromosomes Method: 1. 2. 3. 4. 5. 6. 7. Add a mitotic stimulant to cells i. e. Phytphaemagglutinine Culture for 3 days Add colchicine to the cell culture to arrest the cell at metaphase Burst the cells with hypotonic saline to release chromosomes Stain the chromosomes (Giemsa) Photograph the stained chromosomes Arrange the chromosomes pictures 16

9/25/2020 KARYOTYPING 17

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9/25/2020 NORMAL KARYOTYPE WITH G BANDING 19

9/25/2020 WHAT IS THE ABNORMALITY 20

9/25/2020 OTHER METHODS OF CHROMOSOME ANALYSIS 21

9/25/2020 FISH Method in brief A A T T T A Complementary Fluorescent probe 22

9/25/2020 FISH 23

9/25/2020 FISH image of chromosomes with a probe that 'paints' chromosome 10. Note the extra chromosome 10 material on chromosome 2, which is abnormal. 24

9/25/2020 COMPARATIVE GENOMIC HYBRIDIZATION Identifies abnormal areas in chromosomes (i. e. in tumor cells) No need to use the dividing cells 25

9/25/2020 CHROMOSOMAL ABNORMALITIES The next lecture 26

9/25/2020 REFERENCE 27