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). In the present slide, the structural chromosomal aberration is discussed. The diseases caused due to such aberrations are also explained. Hope you all enjoy. Feel free to comment if have any further clarifications.
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.
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
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
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.
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