structural Aberrations in chromosomes

1. STRUCTURAL CHANGES
IN
CHROMOSOMES
ABDUL JALEEL K
ASSIST. PROFESSOR
GOVT. COLLEGE KASARAGOD
jaleelkabdul@gmail.com

2. Any deviation from normal structure of
chromosome is called structural abnormality

3. • Structural changes usually take place either
during interphase or early prophase
• Structural changes occur due to breakage and
reunion of the chromosome.
• Structural changes lead to alteration in
phenotype, fertility, viability and karyotype of
an individual.

4. DELETION
DUPLICATION
INVERSION
TRANSLOCATION

5. 1. Deletion
Deletion refers to loss of a portion of segment from a chromosome. It is also known as
deficiency.

6. A. Terminal Deletion:
Loss of either terminal segment of a chromosome is known as terminal deletion.

7. B. Interstitial Deletion:
Loss of a segment of chromosome from the intermediate portion or between telomere and
centromere is known as interstitial or intercalary deletion.

8. Cri-du-chat syndrome in human
• In Cri-du-chat syndrome, deletion of terminal
segment of the short arm (q) of chromosome
number 5.

9. 2. Duplication
Presence of segment of chromosome in excess of the normal is called as duplication.

10. A. Tandem duplication
Sequence of genes in the duplicated segment is similar to the sequence of genes in the
original segment of a chromosome.

11. B. Reverse Tandem duplication
The sequence of genes in the duplicated segment is reverse to the sequence of genes in the
original segment of a chromosome.

12. C. Displaced duplication:
When the duplication is found away from the original segment but on the same arm of the
chromosome, it is known as displaced duplication.

13. D. Reverse Displaced
Such duplication is also away from the original segment but in reverse to the sequence of
genes in the original segment of a chromosome.

14. Inversion:
Inversion refers to structural change in a chromosome in which a segment is oriented in a
reverse order. Thus the inverted segment is rotated to a full 180°.

15. A. Paracentric Inversion:
Centromere is not involved. Both breaks occur in one arm of the chromosome.

16. B. Pericentric Inversion:
Centromere is involved. Break occurs in each of the two arms of a chromosome.

17. 3. Translocation:
One way or reciprocal transfer of segments between non-homologous chromosomes is known
as translocation.

18. Translocations
• A. Simple Translocation
• B. Shift translocation
• C. Reciprocal translocation

19. A. Simple Translocation
When a segment from one chromosome is transferred and attached to the end of a
non-homologous chromosome, it is known as simple translocation

20. B. Shift translocation
Transfer of an intercalary segment from one chromosome to the intercalary position in
a non-homologous chromosome is referred to as shift.

21. C. Reciprocal translocation
Mutual exchange of segments between non-homologous chromosomes is known as reciprocal
translocation

22. Balanced translocation

23. Robertsonian translocation
A reciprocal translocation between two acrocentric chromosomes may produce a dot or
microchromosome and metacentric chromosome this phenomenon is known as Centric fusion
or Robertsonian translocation.

24. Philadelphia chromosome
The chromosome abnormality that causes chronic myeloid leukemia (CML). It is an abnormally
short chromosome 22 that is one of the two chromosomes involved in a translocation with
chromosome 9.