Dr Maninder chromosomal abberations.pptx

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1. Structural and numerical alterations of chromosomes, Ploidy and their genetic implications Dr. Maninder Jeet Kaur Assistant Professor CGC, Landran

2. “C hromosomal aberrations are any type of change in the chromosome structure or number.” OR “Spontaneous variation in chromosome number or structure do arise in nature; these variations are called chromosomal aberrations” What Are Chromosomal Aberrations?

3. TY P ES OF CHRO M O S OME AB E R R A TIONS STRUCTURAL CHANGES NUMERICAL CHANGES

4. Types Of Chromosomal Aberrations STRUCTURAL ABERRATIONS NUMERICAL ABERRATIONS 1. DELETION 2. DUPLICATION 3. INVERSION 4. TRANSLOCATION 1. ANEUPLOIDY 2. EUPLOIDY 4

5. Structural Aberrations Structural chromosomal aberrations alter the chromosome structure i.e. the number, the sequence or the kind of genes present in chromosome(s) 5

6. Types Of Structural Chromosomal Aberrations

7. “Loss of chromosome segment, together with genes contained in it” Types of Deletion A. Terminal B. Interstitial Heterozygous deletion Homozygous deletion DELETION

8. GENETIC EFFECTS: Fertility Viability Crossing over Phenotype Change in Karyotype

9. Duplication Gain of a segment of a chromosome in the genome is called a duplication . As a result of it, a set of genes gets doubled or repeated. The extra set of genes is generally called “repeat ”. Types of Duplications: Tandem Reverse Tandem Displaced Reverse Displaced Genetic Effect Phenotype Crossing over

10. Inversion Inversion are those structural change in chromosomes in which a segment is oriented in a reverse order.

11. Types of Inversion : Paracentric Pericentric

12. Genetic effects Fertility Crossing over Gene order

13. Translocation One way or reciprocal exchange of segments between non- homologous chromosome . Types of Translocation: Simple Translocation Shift Translocation Reciprocal Translocation Origin of Translocation: Translocation originate through breakage and exchange of parts between non- homologous chromosomes.

14. Genetic effects Sterility Crossing over phenotype

15. NU M E R I C A L ALTERATIONS IN C H R O M O SOME A deviation from the diploid (2n = 2x) state represents a numerical chromosomal aberration . Types of Numerical Changes Aneuploidy: A loss or gain of one or few chromosomes of a species i.e. from 2n state is known as aneuploidy. Euploidy: It have one or more complete genomes which may be identical with or distinct from each other.

16. Types of Aneuploidy : (A) Hypoploidy ( B) Hyperploidy Monosom y (2n-1) (i ) Trisom y ( 2n+1 ) Nullisomy (2n-2) (ii) Polysomy ( > 2n+ 1 )

17. 1.Monosom y (2n-1): Loss of a single chromosome in diploid state. Monosomics have been reported in Drosophila, Nicotiana, Maize, Wheat, Cotton, Oat etc. 2 . Nullisom y (2n-2): An individual lacking one pair of homologous chromosome from a diploid set.

18. 1. TRISOMY (2n+1 ): Addition of one chromosome to one pair in a diploid set is known as trisomy (2n+1). Trisomy were first reported by Blakeslee in 1910 in Datura . Reported in tomato, Nicotiana , Secale cereale and Pisum sativum etc.

19. Polysomy ( > 2n+ 1) In tetrasomic (2n+2) individuals, somatic cells contain one pair of a chromosome in excess of the normal . Morphological effects of Tetrasomy: In general, gain of a chromosome pair is more deleterious than that of one chromosome. Therefore, few tetrasomics of diploid species can be recovered and maintained. Tetrasomics are viable in polyploid species, e.g., Wheat.

20. TYPES OF EUPLOIDY Monoploidy: Presence of a single copy of a single genome. It is represented by x. Haploidy: A cell or organism having the gametic chromosome number. It is represented by n. Polyploidy: Presence of more than two genomes in an individual.

21. Types of polyploidy AUTOPOLYPLOIDY : More than two copies of same genome ALLOPOLYPLOIDY : When there are 2 or more distinct genomes AUTOTRIPLOID Three copies of same genome present 2n=3x AUTOTETRAPLOID Four copies of the same genome present 2n=4x AUTOPENTAPLOID Five copies of the same genome present 2n=5x AUTOHEXAPLOID Six copies of same genome 2n=6x ALLOTETRAPLOID Two distinct genomes each has 2 copies (2x 1 + 2x 2 ) ALLOHEXAPLOID Three distinct genomes each has 2 copies (2x 1 +2x 2 +2x 3 ) ALLOCTAPLOID Four distinct genomes each has 2 copies (2x 1 +2x 2 +2x 3 +2x 4 ) THANK YOU!