Structural Chromosomal aberrations (Change in Structure of Chromosome)

this presentation is about chromosomal aberration especially change in structure of chromosome. different types of structural chromosomal aberrations are also discussed. effects of different aberration are also included.

1. Structural Chromosomal Aberrations BY ASAD KHAN

2. Contents of Presentation What are chromosomes? Introduction to Chromosomal Aberrations History of Chromosomal Aberrations Structural Chromosomal Aberrations Types of structural Chromosomal Aberrations Use of structural chromosomal aberrations Reference

3. What are chromosomes?

4. What are chromosomes? Tiny thread-like structures found in the nucleus of most living cells Carriers of genetic information in the form of genes. Made up of protein (histone) and DNA. Each human normally has 23 pairs of chromosomes, 46 in number.

5. Discovery of Chromosomes Chromosomes were first described by Strausberger in 1875. The term “Chromosome”, however was first used by Waldeyer in 1888 . They were given the name chromosome (Chromo = color; Soma = body) due to their marked affinity for basic dyes . Their number can be counted easily only during mitotic metaphase.

6. Chromosomal Aberrations

7. Chromosomal aberrations A  chromosome aberration,  disorder, anomaly , abnormality   , or mutation is a missing, extra, or irregular portion of chromosomal DNA . OR Mutations that cause change in the structure or number of chromosomes are called chromosomal aberrations. Generally , the incidence of chromosomal abnormalities is 5-6 persons/1000. Many children with a chromosomal abnormality have mental or physical birth defects.

8. History of Chromosomal Aberrations In 1959 two discoveries opened a new era of genetics. Jerome Lejeune, Marthe Gautier, and M. Raymond Turpin discovered the presence of an extra chromosome in Down syndrome patients. C . E. Ford and his colleagues, P. A. Jacobs and J. A. Strong first observed sex chromosome anomalies in patients with sexual development disorders.

9. Types of chromosomal aberrations

10. Structural Chromosomal aberrations

11. Structural chromosomal aberrations The mutations or changes that occur in structure of chromosome are structural aberrations. Also known as Chromosome Rearrangement. S equence of Genes kind of genes in chromosome no . of genes

12. TYPES OF STRUCTURAL ABERRATIONS

13. TYPES OF STRUCTURAL ABERRATIONS Common types of structural aberrations:- Deletion Duplication Inversion Translocation Insertion Ring chromosome

14. DELETION OR DEFICIENCY The loss of part of chromosome is called deletion. An event in which a piece of chromosome is missed or deleted. Can remove one or more genes from chromosome. Deletion was the first structural aberration detected by Bridges in 1917 from his genetic studies on X chromosome of Drosophila. causes several serious genetic diseases.

15. Cont.……. Deletion may occurs due to (a)   Losses from translocation (b)  Crossovers within an inversion (c)   Unequal crossing over (d)  Breaking without rejoining

16. Types of deletion Terminal Deletion In this case loss of a terminal segment occurs, with a single break in the chromosomes Intercalary Deletion In this case, internal part of a chromosome is missing.

17. EFFECTS OF DELETION Homozygous deletions are lethal. They cause abnormal developments. Deletion involves the loss of genes so they have deleterious effect on organisms If the lost genes are crucial for viability, sterile gametes or non functional somatic cells may result In human genome deletion mutation cause: Granulocytic leukemia Cri-du-chat syndrome

18. Duplication Duplication is the doubling or repetition of chromosome segment during chromosome duplication As a result of it, a set of genes gets doubled or repeated The extra set of genes is generally called “ repeat ” Duplication was first detected by Bridges in 1919 from his genetic studies on X chromosome of Drosophila .

19. Types of duplication 1 . Tandem Duplication The extra segment and the parent segment are next to each other and have the same order of genes 2. Reverse tandem duplication The extra segment lies next to parent segment with reversed gene sequence 3. Displaced duplication The duplicate segment lies some distance away from the parent segment

20. EFFECTS OF DUPLICATION Duplications are more frequent and less deleterious than deletions Duplications are believed to be the important raw materials of organic evolution Large duplications affect the regulation of gene activity and there by causes phenotypic alterations which in turn promotes speciation and evolution

21. inversion In this case, the fragment reattach to the original chromosome but in reverse orientation OR Inversion is the reversal of the linear order of a chromosome segment and its gene sequence Chromosomal inversion may be paracentric or Pericentric. In Paracentric inversion both breaks occur in one arm; centromere is not involved. In Pericentric inversion breaks occur on both arms; Centromere is involved.

22. EFFECTS OF INVERSION Helps to retain the original gene combination by reducing the crossing over frequency Inversion enhances the position effect & there by produces phenotypic changes Inversion causes chromosome polymorphism with in a population leading to karyotype evolution Inversion produces balanced gene complexes(super genes) through reduction of crossing over, which in turn confers greater biological fitness and adaptability & increases the evolutionary potentiality

23. CHROMOSOMAL TRANSLOCATION two pieces of different chromosomes are interchanged. A portion of one chromosome is transferred to another chromosome.

24. Types of translocation Intrachromosomal translocation Change in position of a segment within a chromosome, either from one arm to the other or from one location to another in the same arm Intraradial Translocation from one location to another in the same arm Extraradial Translocation from one arm to the other Interchromosomal Translocation Transfer of a segment from one chromosome to other Transpositional translocation one way transfer of a chromosome segment from one portion to another in the same chromosome Reciprocal Translocation mutual exchange of segments between two chromosomes

25. Effects of translocations Cause diseases in human such as cancer and infertility. It may causes changes in chromosomes & also in gene combinations, promoting variation, speciation, & evolution

26. insertion An event in which a piece of the chromosome is removed and inserted into a different or another chromosome. In insertion segments of DNA can also move from chromosome to chromosome . It results in loss of genetic material from one chromosome .

27. Ring Chromosome ring chromosome is a chromosome whose arms have fused together to form a ring. Were first discovered by Lilian Vaughan Morgan in 1926. Denoted by symbol r in human genetics or R in Drosophila genetics.

28. Uses of structural aberration

29. Uses of structural aberration Study of chromosome pairing and its behavior during cell division For locating genes on particular chromosome To resolve special problems such as relation between chiasma and crossing over Used in plant breeding by increasing the dosage of certain desirable genes for increasing the activity New genes can be produced only through duplications

30. Cont.…… Important role in evolution Desirable characters can be detected using inversion Translocation used in determination of unknown locus of gene and chromosome mapping Used to know the point of initiation of chromosome pairing

31. references

32. . https:// www.slideshare.net/SaadiyahArif/chromosomal-aberration-75945151 https:// www.slideshare.net/mujahidhussain63/7-chromosomal-aberrations https:// www.slideshare.net/geetavin/chromosomal-aberrations http:// www.biologydiscussion.com/genetics/structural-change-in-the-structure-of-chromosomes/5261 https://biologyboom.com/chromosome-aberration / https:// en.wikipedia.org/wiki/Chromosome_abnormality

33. The end

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