Karyotyping

Karyotyping Chromosome Banding Chromosomal aberrations chromosome visualization

1. KARYOTYPING Presented by JISHNU V M M.Phil. Scholar Dept. of Botany Kariavattom

2. Karyotyping is the process by which photographs of chromosomes are taken in order to determine the chromosome complement of an individual, including the number of chromosomes and any abnormalities. The term  karyotype  is also used for the complete set of chromosomes in a species or in an individual organism and for a test that detects this complement or measures the number. The study of whole sets of chromosomes is sometimes known as  karyology . The chromosomes are depicted (by rearranging a photomicrograph) in a standard format known as a  karyogram  or  idiogram : in pairs, ordered by size and position of centromere for chromosomes of the same size etc.

3. The term karyotyping derived from Greek word “ karyon ”, which means "kernel", "seed", or "nucleus", it is represented as Idiogram . When the haploid set of chromosomes of an organism are ordered in a series of decreasing size, it is said to be an Idiogram . In other sense diagrammatic representation of a karyotype is an Idiogram .

4. Karyotyping Size of chromosome Position of centromere Presence of 2 constriction Size of satellite

5. Human karyotype (male)

6. HIS-STORY Chromosomes were first observed in plant cells by Carl Wilhelm von Nageli in 1842. Their behaviour in animal (Salamander ) cells was described by Walther Flemming , the discoverer of mitosis, in 1882. The name was coined by another German anatomist, Heinrich von Waldeyer in 1888. Joe Hin Tjio working in Albert Levan's lab found the Human chromosome count to be 46 using new techniques available at that time. Grygorii Levitsky (1931) seems to have been the first person to define the karyotype as the “phenotypic appearance of the somatic chromosomes, in contrast to their genic contents”.

7. TYPES OF KARYOTYPES Asymmetric Karyotype • Show larger difference between smaller and larger chromosome in a set. • Have more acrocentric chromosomes. • Have relatively advanced feature Symmetric Karyotype • Show lesser difference between smaller and larger chromosome in a set. • Have more metacentric chromosomes. • Have no relatively advanced feature

8. Characteristics of Karyotyping Differences in absolute sizes of chromosomes ( Lotus tenuis and Vicia faba ). Differences in the position of centromeres. Differences in the relative size of chromosomes. Differences in basic number of chromosomes (the dislocation hypothesis) or through fusion. Differences in number and position of satellites. Differences in degree and distribution of heterochromatic regions.

9. Human Karyotyping

10. Chromosomal changes Karyotyping is mostly performed to see the chromosomal changes. There are two type of changes: 1. Structural changes and 2. Numerical Changes Structural changes: Change of structure is referred to as chromosomal aberrations or chromosomal mutations .

11. Structural changes Changes in number of genes in a chromosome • Deletion. • Duplication. Changes in the arrangement of genes • Inversion • translocation Structural changes of chromosome

12. Numerical Changes Numerical change in chromosome or variations in chromosome number can be mainly of two types, namely: • Aneuploidy and • Euploidy Aneuploidy • It involves addition or deletion of one or few chromosomes to the usual diploid set of chromosomes. • The aneuploids arise due to failure of the separation of homologous chromosomes of particular pair during meiosis.

13. Aneuploidy Aneuploids are of following types: • Nullosomy • Monosomy • Trisomy • Tetrasomy Euploidy Organism with one complete set of chromosome is said to be euploid . Euploidy is of following types: • Monoploidy • Polyploidy

14. Aneuploidy Variations in the number of individual chromosomes Nullosomy Loss of one chromosome pair (2n – 2, where 2n is the complete set of chromosome of an individual). Monosomy Loss of a single chromosome from the chromosome set (2n – 1). Trisomy One extra chromosome in the set of chromosome (2n + 1). Tetrasomy One extra chromosome pair in the set of chromosome (2n+2).

15. Aneuploid condition in human Autosomal

16. Sex chromosomal

17. Trisomy 9, believed to be the 4th most common trisomy, trisomy 9p syndrome or mosaic trisomy 9. They often function quite well, but tend to have trouble with speech. Trisomy 8 and trisomy 16, although they generally do not survive to birth. Some disorders arise from loss of just a piece of one chromosome 1p36 Deletion syndrome, from the loss of part of the short arm of chromosome.

18. Angelman syndrome – 50% of cases have a segment of the long arm of chromosome 15 missing; a deletion of the maternal genes, example of imprinting disorder. Prader -Willi syndrome – 50% of cases have a segment of the long arm of chromosome 15 missing; a deletion of the paternal genes, example of imprinting disorder. Chromosomal abnormalities can also occur in cancerous cells Philadelphia chromosome, a translocation mutation commonly associated with chronic myelogenous leukemia and less often with acute lymphoblastic leukemia

19. CHROMOSOME BANDING

20. Chromosomes display a banded pattern when treated with some stains. Bands are alternating light and dark stripes that appear along the lengths of chromosomes. Unique banding patterns are used to identify chromosomes and to diagnose chromosomal like G-bands, R-bands, C-bands, Q-bands, T-bands and NOR-bands. This banding pattern is used to identify each chromosome and to diagnose Chromosomal aberrations Chromosomal breakage Loss Duplication or inverted segments These staining techniques used to make the bands visible were developed in the late 1960s and early 1970s.

21. Mostly metaphase chromosomes whose size has condensed and whose diameter is increased are used for chromosome banding studies after fixing the stage. Classification of Banding Techniques Based on GC and AT rich regions Based on Constitutive Heterochromatin Region

22. Karyogram from a human female lymphocyte probed for the Alu sequence using FISH

23. Spectral karyotyping (SKY technique) In spectral karyotyping, image processing software assigns a pseudo colour to each spectrally different combination, allowing the visualization of the individually coloured chromosomes by using an interferometer attached to a fluorescence microscope. Spectral human karyotype Spectral karyogram of a human female

24. Advantages of Karyotyping Reveals structural features of each chromosomes. Helps in studying chromosome banding pattern. Helps in the identification of chromosomal aberrations. Diagnosis of prenatal genetic defects. Aids in studying evolutionary changes.

25. References Text Book of Genetics, Richard Robinson, The Macmillan Science Library, Volume 1; Pp: 125-129. Encyclopedia of Molecular Biology, Pp: 2347. Gupta, P. K., 2012. Cytogenetics an advanced study, Chapter 1: 3-16. Wendy, A. B.,2001. Karyotype analysis and chromosome banding. Nature, 1-6. Moore, C. M. and Best, R. G., 2002. Chromosome preparation and banding. Nature, 1- 6. Ried , T., et.al ,1998. Chromosome painting : a useful art. Human Molecular Genetics, Vol(7),1619- 1626.