This document discusses chromosomes, their structural and functional importance, and details chromosomal aberrations, which are abnormalities in chromosome structure or number that can lead to genetic disorders. It outlines the types of chromosomal aberrations, specifically structural (deletion, duplication, inversion, translocation) and numerical (aneuploidy, polyploidy), along with examples of associated disorders. Additionally, information on the mechanisms behind these aberrations and associated conditions is provided.

1. STRUCTURAL
CHROMOSOMAL
ABERRATIONS
Vinitha S Babu

2. What are chromosomes?
Chromosomes are thread-like structures located inside the nucleus of animal
and plant cells.
Each chromosome is made of protein and a single molecule of
deoxyribonucleic acid (DNA).
Passed from parents to offspring, DNA contains the specific instructions that
make each type of living creature unique.
The term chromosome comes from the Greek words for color (chroma) and
body (soma).
Strongly stained by some colorful dyes used in research.

3. Structure and types of Chromosomes

4. Chromosomal Aberrations
Chromosomal aberrations are abnormalities in the structure or number of
chromosomes and are often responsible for genetic disorders.
These events may occur spontaneously or can be induced by environmental
agents such as chemicals, radiation, and ultraviolet light.
However, mutations are most likely due to mistakes that occur when the genes
are copied as the cells are dividing to produce new cells.

5. Types of Chromosomal aberrations
Two types of aberrations:
I. Structural
1. Deletion
2. Duplication
3. Inversion
4. Translocation
II. Numerical
1. Aneuploidy
2. Polyploidy

6. Structural Aberrations
1. Deletion
2. Duplication
3. Inversion
4. Translocation
Changes involving the
number of genes
Changes involving the
arrangement of genes

7. 1. Deletion
Loss of a region of chromosome
Occurs when a chromosome breaks and a fragment is lost
2 types
Terminal
Intercalary

8. Types of Deletion

9. Deletion Loop Formation

10. Disorders
Cri- du- chat Syndrome: Deletion of 5p
DiGeorge Syndrome: Deletion of 22q
Angelman Syndrome: Partial deletion of 15q
Jacobsen Syndrome: Deletion of 11q
Wolf Hirschhorn Syndrome: Deletion of 4p

11. 2. Duplication
Caused by abnormal events during recombination
Just opposite of deletion
Extra copies of chromosomal regions are formed

12. Types of duplication

13. Loop formation in duplication

14. Deficiency Disorder
Charcot Marie-Tooth Disease Type 1A: Duplication of gene PMP
(Peripheral Myelin Protein) 22 on chromosome 17

15. 3. Inversion
It is a chromosome rearrangement in which a segment of
a chromosome is reversed end to end.
An inversion occurs when a single chromosome undergoes
breakage and rearrangement within itself: Breakage-reunion
hypothesis

16. Types of inversions
2 types:
1. Pericentric
2. Paracentric

17. 4. Translocation
Here, a part of one chromosome breaks off and sticks to
another chromosome
2 types;
1. Reciprocal Translocation: Segments from 2 different chromosomes are exchanged
2. Robertsonian Translocation: An entire chromosome has been attached to another
at the centromere region. It occurs in five acrocentric pairs as 13, 14, 15, 21, 22.

18. Reciprocal Translocation

19. Robertsonian Translocation
Discovered by W R B Robertson who discovered in grasshoppers in 1916
Two acrocentric chromosomes are generally involved
Occurs 1/1000 live births
2 types
i. Homologous acrocentric
ii. Non homologous acrocentric

20. Chronic Myelogenous Leukemia

21. Summary
Chromosomes: Structure, Types
Chromosomal Aberration
Types of chromosomal aberrations
Structural aberrations

22. Thank You