Chromosome number shape and size

1. Chromosome number, shape &
types

2.  Chromosome ( croma- color,soma- body)
 In the nucleus of each cell, the DNA molecule is tightly
packaged into thread-like structures called chromosomes
.
 Chromosomes are thread-like structures in which DNA is
tightly packaged within the nucleus.
 Discovered by strausberger in 1875 & term
chromosome coined by waldeyer 1888.
 visible under a light microscope only when the cell is
undergoing the metaphase of cell division.
 Chromosomes are vary in number,shape and size

3.  Chromosome number
• Each species has its own characteristic number of
chromosomes and varies from some species to species.
• Sexually reproducing species Somatic or body cells, which
are DIPLOID [2n] having two sets of chromosomes, one
from the mother and one from the father
• Asexually reproducing species have one set of
chromosomes that are the same in all body cells. However,
asexual species
can be either haploid or diploid
Organisms Chromosom
e no
Human 46
Chimpanzee 48
House mouse 40
Maize 20
 Concept of
1)euploidy
2)aneuploidy

4. Shape of chromosome
• The shape of chromosome usually determine by
the position of the centromere
• Chromosomes are generally exits in three
different shapes as fallow-
1) rod shape
2)“J "shaped
3)“V" shaped
Or terminal, sub-terminal
or median in positions

5. Types of chromosome
Human Chromosome type can be divided into-
1) Autosomes
2) Allosomes ( X or Y)
Chromosome types- based on centromere number
1)Acentric
2)Monocentric
3)Dicentric
4)polycentric

6. Type of chromosome
Based on position of centromere -
1) Metacentric
2) Sub-metacentric
3) Acrocentric
4)Telocentric
5) Subtelocentric
6) Holocentric