Architecture of Chromosome
Chromosome, the microscopic threadlike part of the
cell that carries hereditary information in the form of
genes.
Chromosome= chroma (colour) + some (body)
In 1842, Karl Wilhelm von Nageli, a swiss botanist
first observed the rod-like structure present in the
nucleus of the plant cell.
Chromosomes were first discovered by Strasburger
in 1815 .
Walter Sutton and Theodor Boveri in 1902
suggested that chromosomes are the physical carrier
of genes in the eukaryotic cells.
Centromere or Kinetochore:
It is the primary constriction at the center to which the chromatids or spindle fibers are attached. Its function is to enable movement of the chromosome during the anaphase stage of cell division.
Chromatid:
Each chromosome has two symmetrical
structures called chromatids or sister chromatids which is
visible in mitotic metaphase.
› Each chromatid contains a single DNA molecule.
Chromatin:
It is a complex of DNA and proteins that forms
chromosomes within the nucleus of eukaryotic cells.
Thedarkly stained, condensed region of chromatin is
known as heterochromatin. It contains tightly
packed DNA, which is genetically inactive
The light stained, diffused region of chromatin is
known as euchromatin. It contains genetically
active and loosely packed DNA
Telomere:
A telomere is the end of a chromosome. Telomeres are made of repetitive sequences of non-coding DNA that protect the chromosome from damage. Each time a cell divides, the telomeres become shorter. Eventually, the telomeres become so short that the cell can no longer divide.
Karyotype:-
The characteristics features of chromosome of a species is referred as karyotype
Its phenotypic appearance of the chromosomes of a
particular species.
Two types – Symmetrical and Asymmetrical
Features taken into consideration in karyotype study
1. Number
2. Position of centromere
3. Size
4. Position of satellite
5. Degree and distribution of heterochromatin