CHROMOSOMES - Dr. P. Saranraj, Assistant Professor, Department of Microbiology, Sacred Heart College (Autonomous), Tirupattur, Vellore District, Tamil Nadu, India.
Climate Change Impacts on Terrestrial and Aquatic Ecosystems.pptx
Chromosomes
1. Dr. P. Saranraj M.Sc., M.Phil., Ph.D., NET
Assistant Professor
Department of Microbiology
Sacred Heart College (Autonomous)
Tirupattur, Vellore District.
Mobile: 9994146964
E.mail: microsaranraj@gmail.com
2. CHROMOSOMES
In the nucleus of each cell, the DNA molecule is packaged
into thread-like structures called Chromosomes.
Chromosomes were first described by Straubberg in 1875.
The trem Chromosomes was coined by Waldeyer in 1888.
Each chromosome is made up of DNA tightly coiled proteins
called Histones that support its structure.
Chromosomes are not visible in the cell’s nucleus not even
under a microscope when the cell is not dividing. However,
the DNA that makes up chromosomes becomes more tightly
packed during cell division and is then visible under a
microscope.
Human cells have 46 Chromosomes (23 Identical pairs) (44
Autosomes and 2 Sex Chromosomes) (Autosomes are the
chromosomes which are not involved in sex determination)
3. Organisms Number of chromosomes
Human 46
Chimpanzee 48
Dog 78
Horse 64
Chicken 78
Goldfish 94
Fruit fly 8
Mosquito 6
Nematode 11(m), 12(f)
Round worm 2
8. STRUCTURE OF CHROMOSOMES
Centromere – It is a part of chromosomes that
links sister chromatids. Centromere gives the
characteristic shape to the chromosomes and helps
describe the location of specific genes.
“P” arm – It is a short arm which is present in
upward.
“Q” arm - It is a long arm which is present in
downward.
9. Telomere – It is present in the tips of chromosome.
Chromatids – Two identical copies formed by the
replication of two chromosomes.
Chromatins – Chromatin is a complex of DNA and
Protein found in the eukaryotic nucleus which
packages chromosomes. The structure of the
chromatin varies significantly between different
stages of cell cycle according to the requirement of
DNA
12. 2. ACROCENTRIC
The Centromere is almost terminal.
It has one large and another very small arm.
LONG ARM
CENTROMERE
SHORT ARM
13. 3. SUB - METACENTRIC
The Centromere is not at the middle position
of the chromosomes.
The arms are unequal and it is ‘L-Shaped’ in
appearance.
CENTROMERESHORT ARM
LONG ARM
14. 4. METACENTRIC
The Centromere is at the middle position.
The arms are equal and it is ‘V-Shaped’ in
appearance.
TWO EQUAL ARMS
CENTROMERE