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.

2. STRUCTURAL CHROMOSOMAL
ABERRATIONS
BY ASAD KHAN

3. CONTENTS OF PRESENTATION
1. What are chromosomes?
2. Introduction to Chromosomal Aberrations
3. History of Chromosomal Aberrations
4. Structural Chromosomal Aberrations
5. Types of structural Chromosomal Aberrations
6. Use of structural chromosomal aberrations
7. Reference

4. WHAT ARE
CHROMOSOMES?

5. 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.

7. 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.

8. CHROMOSOMAL
ABERRATIONS

9. 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.

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

11. TYPES OF CHROMOSOMAL
ABERRATIONS

12. STRUCTURAL CHROMOSOMAL
ABERRATIONS

13. STRUCTURAL CHROMOSOMAL
ABERRATIONS
The mutations or changes that occur in structure of chromosome
are structural aberrations.
Also known as Chromosome Rearrangement.
Sequence of Genes
kind of genes in chromosome
no. of genes

14. TYPES OF STRUCTURAL
ABERRATIONS

15. TYPES OF STRUCTURAL
ABERRATIONS
Common types of structural aberrations:-
1. Deletion
2. Duplication
3. Inversion
4. Translocation
5. Insertion
6. Ring chromosome

16. 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.

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

19. 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.

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

21. 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.

22. 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

24. 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

25. 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.

27. 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

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

29. 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

31. 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

32. 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.

34. 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.

37. USES OF STRUCTURAL
ABERRATION

38. USES OF STRUCTURAL
ABERRATION
1. Study of chromosome pairing and its behavior during cell division
2. For locating genes on particular chromosome
3. To resolve special problems such as relation between chiasma and
crossing over
4. Used in plant breeding by increasing the dosage of certain
desirable genes for increasing the activity
5. New genes can be produced only through duplications

39. CONT.……
6. Important role in evolution
7. Desirable characters can be detected using inversion
8. Translocation used in determination of unknown locus of gene and
chromosome mapping
9. Used to know the point of initiation of chromosome pairing

40. REFERENCES

41. .
1. https://www.slideshare.net/SaadiyahArif/chromosomal-
aberration-75945151
2. https://www.slideshare.net/mujahidhussain63/7-chromosomal-
aberrations
3. https://www.slideshare.net/geetavin/chromosomal-aberrations
4. http://www.biologydiscussion.com/genetics/structural-change-
in-the-structure-of-chromosomes/5261
5. https://biologyboom.com/chromosome-aberration/
6. https://en.wikipedia.org/wiki/Chromosome_abnormality

42. THE END

43. THANKS