1. Chromosome and its structure
Chromosome morphology
P. Victoria Rani
Lecturer in Botany
D.K. Govt Degree college for women (A),
NELLORE
Dr P. Victoria Rani
Lecturer in Botany
V Sem, Cell Biology Genetics and Plant Breeding (Paper V)
D.K. Govt Degree college for women (A),
NELLORE

2. INTRADUCTION Chromosome means: chroma - colour; soma – body
A chromosome is a thread-like self-replicating genetic
structure and containing organized DNA molecule.
Chromosomes are seen in the metaphase stage of mitosis.
Hofmeister in 1848 discovered thread-like structures from pollen mother cells of Tradescancia.
Waldeyer coined the term chromosome first time in 1888
Chromosomes are considered as Vehicles of Heredity.

3. Polyploidy –Cell contain more than two sets of chromosomes.
Number of chromosome
The number, size of chromosomes varies from species to species.
Diploid -The somatic chromosome number is the number of chromosomes found in somatic cell and is represented by 2n (Diploid).
Haploid - The gametes have chromosome number is half of the somatic chromosome numbers and represented by n (Haploid).
Polyploidy –Cell contain more than two sets of chromosomes.

4. Number of chromosomes
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6. Types of chromosomes Chromosomes are of two types
Autosomes: That control somatic characters other than sex characters.
Sex chromosomes – Chromosomes involved in sex determination. Humans and most other mammals have two sex chromosomes X & Y, also called heterosome.
Females have two X chromosomes in diploid cells and males have an X and a Y chromosome.

7. The size of chromosome Chromosome shape
Short as 0.25 µm in fungi and some birds or as long as 30 µm in some plants like Trillium.
Chromosome shape
1. Telocentric
2.Acrocentric
3.Sub-metacentric
4.Metacentric

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9. Chromosome Structure Chromosome consists Pellicle Matrix Chromonema
Chromomeres
Centromere or primary constriction
Secondary constriction
Satellite bodies
Telomeres

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13. Prophase and metaphase
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15. Mitosis metaphase
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16. Functions of Chromosomes
Control the Heredity
Control the metabolism of an organism
Changes in the position, number and structure of Chromosomes lead to the formation of new species.

17. Karyotype
It is refers to the entire set of chromosomes present in the cell.
Idiogram
The photograph showing the chromosomes of a cell.

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19. Chemical composition of chromosomes
Proteins- 60% (protamines, histones)
DNA-35%
RNA-5%
Protamines
Basic protein rich in the basic amino acid orginine
Histones
Rich in the basic amino acid orginine and lysine
Histones are H1,
H2a
H2b
H3 and
H4.

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21. NUCLEOSOME
The DNA wraps around the histone proteins to form a bead like structure which consist core, core DNA and linker DNA.
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22. compactly coiled regions deeply stained Silent genes with methylated
Chromosome parts
Heterochromatin.
compactly coiled regions
deeply stained
Silent genes with methylated
High AT content
less active
Euchromatin
loosely coiled regions.
less stained
active or potentially active genes
genetically active

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