This document summarizes key information about chromosomes. It defines chromosomes as carriers of genetic information visible during cell division. It describes the differences between prokaryote and eukaryote chromosomes. It discusses chromosome number, size, and types (autosomes and sex chromosomes). It explains cell division processes like meiosis and fertilization. It provides examples of human chromosomal abnormalities including both numerical disorders like Down syndrome and structural disorders. It describes chromosome structure and banding patterns used to identify chromosomes. It concludes with references for further reading.

1. A
Seminar on
CHROMOSOMES
Presented
By
K. GANAPATHI RAO
(13031D6003)
Presence of
Miss. CH SILPA CHAKRA
(HOD) CNST-JNTUH IST

2. OUTLINE
•
•
•
•
•
•
•
•
Introduction.
Chromosome.
Types Of Chromosomes.
Cell Division.
Meiosis And Fertilisation.
Human Chromosomal Abnormalities.
Chromosomes Structure.
Structural Chromosomes Disorders.

3. CELL
• Basic unit of building the body

4. Chromosomes In Different Cells
PROKARYOTES
EUKARYOTES
single chromosome plus plasmids
many chromosomes
circular chromosome
linear chromosomes
made only of DNA
made of chromatin, a nucleoprotein
(DNA coiled around histone
proteins)
found in cytoplasm
found in a nucleus
copies its chromosome and divides copies chromosomes, then the cell
immediately afterwards
grows, then goes through mitosis to
organise chromosomes in two equal
groups

5. Chromosome
• Chromosomes are the rod-shaped, filamentous bodies
present in the nucleus, which become visible during cell
division.
• They are the carriers of the gene or unit of heredity.
• Chromosome are not visible in active nucleus due to
their high water content, but are clearly seen during
cell division.
• Chromosomes were first described by Strausberger in
1875.
• The term “Chromosome”, however was first used by
Waldeyer in 1888.
Chromo=colour
Soma=body
Chromosome

6. CHROMOSOME

7. NUCLEOSOMES
30 NM SOLENOID/
CHROMATIN FIBER
CHROMATIN FIBER
LOOPS

8. No of chromosomes
• Normally, all the individuals of a species have
the same number of chromosomes.
• Presence of a whole sets of chromosomes is
called euploidy.
• When a change in the chromosome number does
not involve entire sets of chromosomes, but only
a few of the chromosomes - is Aneuploidy.
• Gametes normally contain only one set of
chromosome – this number is called Haploid
• Somatic cells usually contain two sets of
chromosome
– 2n - Diploid
– 3n – triploid
– 4n – tetraploid

9. No of chromosomes
Round worm
Onion
Tomato
2
16
24

10. Chromosome Size
In contrast to other cell organelles, the size of chromosomes shows
a remarkable variation depending upon the stages of cell division.
• Interphase: chromosome are longest & thinnest
• Prophase: there is a progressive decrease in their length
accompanied with an increase in thickness
• Anaphase: chromosomes are smallest.
• Metaphase: Chromosomes are the most easily observed and
studied during metaphase when they are very thick, quite short
and well spread in the cell.

11. Can distinguish chromosomes by “painting” – using DNA
hybridization + fluorescent probes

12. Types of Chromosomes
• Autosomes
– Paired chromosomes with the same length, shape,
centromere location, and genes
– Any chromosome other than a sex chromosome
– Determine size, colour, hair of a body.
• Sex chromosomes
– Members of a pair of chromosomes that differ between males
and females
HOMOGAMETIC
SEX
HETEROGAMETIC
SEX
SEX DETERMINATION
Female XX
Male XY
Presence of Y-chromosome = maleness
(mammals and fish)
Presence of second X-chromosome =
femaleness (Drosophila, the fruit fly)
Male ZZ
Female ZW
Birds, amphibians, reptiles, butterflies,
moths.
Female XX
Male Xo
Grasshoppers

13. CELL DIVISIONS
• Meiosis:
–
–
–
–
A special type of cell division
Used to make sex cells
Meiosis halves the numbers of chromosomes
Meiosis picks one chromosome from each pair at
random and places them in a sex cell. This results in
enormous variation amongst the sex cells
• Mitosis:
– Normal cell division
– Chromosomes are duplicated and distributed
equally

14. Meiosis and fertilisation
Mother
Father
23 pairs of
chromosomes
23 pairs of
chromosomes
Meiosis
23 unpaired
chromosomes
23 unpaired
chromosomes
23 unpaired
chromosomes
Fertilisation
23 pairs of
chromosomes
Child
23 unpaired
chromosomes

16. The inheritance of gender
Is it going to be a boy or a girl?

17. The inheritance of gender
Mother
Father
XX
XY
X
X
X
X
Fertilisation
Y
X
XX
XY
X
XX
XY
Y
Possible
children
Chance of a girl 50%
Chance of a boy 50%

18. Human chromosomal abnormalities
Numerical (Chromosomal Disorders)
•
•
•
•
Trisomy = 3 copies of a single chromosome 47
Monosomy = 1 copy of a single chromosome 45
Triploidy = 3N
Tetraploidy = 4N
Structural (Chromosomal Disorders)
– Deletion
– Duplication
– Translocation (involves 2 chromosomes)

19. Causes of Chromosomal Disorders
• Ionising radiation, autoimmunity, virus infections and
chemical toxins in the pathogenesis of certain disorders.

20. Some Numerical Disorders
 XXY = Klinefelter’s syndrome male
 Feminine character.
 Tall, Normal Intelligence.
 XXX = Trisomy X female
 Produce healthy female.
 XYY = Jacob’s syndrome male
 Height, more active.
 Slightly learning disability.
 Normal intelligence.
 X/XO = Turner syndrome female
• Webbed neck.
• Short height.
• Immature females.

21. Chromosomes Structure
–
–
–
–
Centromere
p arm
q arm
Telomeres

22. Arm
Region
2
p
1
1
Band
2
1
1
1
q
3
Chromosome 17
3
2
1
2
1
5
4
3
2
1
1
2
2
2
Subband
4
3
1
2
3
1
2, 3
4
1
2
3
17 q 1 1 . 2

23. Chromosome Structure Abnormalities
Translocation
Deletion
Derivative
chromosome
Inversion
Insertion
Isochromosome
Ring
chromosome

24. Some Structural Disorders
• Cri-Du-Chat Syndrome
–
–
–
–
#5q Deletion
Moon-shaped face, Heart disease
Mentally retarded, Malformed larynx
Normal lifespan
• Aniridia-Wilms Tumor Syndrome
–
–
–
–
#11p Deletion
Mentally retarded, Growth retarded
Blindness, Tumors on kidneys
Short lifespan
• Thirteen Q Deletion Syndrome
– Mentally retarded, Deformed face
– No thumbs, Heart disease
– Short lifespan

25. Some Structural Disorders
• Prader-Willi Syndrome
–
–
–
–
#15q Deletion
Small bird-like head, Mentally retarded
Respiratory problems
Obesity, Short lifespan
• Eighteen Q Deletion Syndrome
–
–
–
–
–
#18q Deletion
Mentally retarded, Heart disease
Abnormal hands and feet
Large eyes, Large ears
Normal lifespan
• Burkitt Lymphoma
– Translocation of the Myc gene on chromosome 8
– Translocated Myc genes don’t function properly
– Leads to cancer of the lymph nodes

26. Some Structural Disorders
• Cat-Eye Syndrome
–
–
–
–
#22q Deletion
Fused fingers and toes
Mentally retarded, Small jaw
Heart problems, Normal lifespan
• Patau’s Trisomy Syndrome
–
–
–
–
–
–
#13 Trisomy Nondisjunction
Small head, Small or missing eyes
Heart defects, Extra fingers
Abnormal genitalia,
Mentally retarded, Cleft palate
Most die a few weeks after birth
• Four-Ring Syndrome
–
–
–
–
#4 Inversion
Cleft palate, Club feet
Testes don’t descend
Short lifespan

27. Videos
1. What Is A Chromosome.
2. How Dna Is Packaged (Advanced).
3. Chromosome Disorder Outreach Video.
4. Unique Children With Rare Chromosome Disorders.

28. REFRENCE
• Human Chromosomes by Orlando J. Miller,
• Chromosome biology by R. Appels,
• http://www.chromodisorder.org/CDO/
• http://www.genome.gov/26524120
• http://www.youtube.com/watch?v=zf7tbymrv9
o
• http://www.johnkyrk.com/chromosomestructu
re.html