Chromosome for Grade 8. The Basic

1. Chromosome
By: MNV BioScie

2. What is a Chromosome?
a threadlike structure of nucleic acids and
protein found in the nucleus of most living cells,
carrying genetic information in the form of
genes.
Chromosome means: chroma - colour; some - body)
 First described by Strausberger in 1875.
 The term “Chromosome”, however was first used by
Waldeyer in 1888.

5. Autosome
• An autosome is any chromosome that is
not a sex chromosome.
• Each autosome stores many thousands
genes, each of which performs a
unique function in the organism's cells.
• 22 autosomes (chromosomes)
• Both identical both the two sexes.

6. Sex Chromosomes
• Sex chromosomes (Gonosomes) –
Chromosomes involved in sex
determination. 1 sex chromosome.
• Humans and most other mammals have
two sex chromosomes, the X and the Y.
• Females have two X chromosomes in their
cells,
• Sperms have both X and a Y chromosomes
• Egg cells all contain an X chromosome

7. Chromosome number
• Diploid cells (2N) where N- chromosome number have
two. Homologous copies of each chromosome.
• The body cells of animals are diploid.
• Haploid cells (N) have only one copy of each chromosome.
In animals, gametes (sperm and eggs) are haploid.

9. 2 parts:
Chromatids: two
identical parts of
a chromosome
Centromere:
Joins chromatid
together.
• Primary
Constriction

10. Telomere:
• A telomere is a region of repetitive DNA sequence at the
end of chromosome.
• Protects the chromosome from deterioration of rom fusion
with neighboring chromosomes.
Each chromosome has two arms
• p (the short arm)
• q (the long arm).

11. Kinetochore
• A kinetochore is a protein
structure that forms on a
chromatid during cell division
and allows it to attach to a
spindle fiber on a
chromosome.
• Its proteins also help to hold
the sister chromatids together
and play a role in

12. Karyotype
• A karyotype is simply a
picture of a
person's chromosomes
• Two chromosomes
specify sex, XX for female
and XY for male. The rest
are arranged in pairs,
numbered 1 through 22,
from largest to smallest.

13. Types of Chromosomes based on the position of Centromere
1. Metacentric Chromosomes
• The two arms are equal in length
• Appears in ‘V’ shape.
2. Sub metacentric Chromosomes
• Chromatids of one side are slightly longer than the other side
• Resemble the letter ‘L’.
3. Acrocentric Chromosomes
• Centromere is located closer to the end of chromatid
• The small round structure is termed as satellite
• Resemble the letter ‘J’
4. Telocentric Chromosomes
• Centromere at the end of chromosomes
• Not seen in human cells
• Resemble the letter ‘i’

14. Histone
• Histones are a family of basic
proteins that associate with DNA in
the nucleus and help condense it into
chromatin.
 Histone can be grouped into five major
classes: H1/H5, H2A, H2B, H3, and H4
 These are organized into two super-classes
as follows:
 Core histones – H2A, H2B, H3 and
H4
 Linker histones – H1 and H5

15. • A nucleosome is a section
of DNA that is wrapped
around a core of proteins.
Inside the nucleus, DNA
forms a complex with
proteins called chromatin.
• Histones help in order to
fit inside of the nucleus and
take part in the formation
of chromosomes.

16. Chromatin
• Chromatin is a mass
of genetic material
composed of DNA and
proteins that
condense to form
chromosomes.

17. DNA (deoxyribonucleic acid)
• the chemical inside the nucleus of a cell
that carries the genetic instructions for
making living organisms.
• The material inside the nucleus of cells that
carries genetic information.
GENE
• A gene is the functional and physical unit
of heredity passed from parent to
offspring.
• Genes are pieces of DNA, and most genes
contain the information for making a
specific protein