Details of chromosome classification and parts of a typical chromosome

1. CHROMOSOME nomenclature
Dr. Nagabhushan C M
Assistant Professor,
Dept. Of Studies in Zoology,
Vijayanagara Sri Krishnadevaraya University,
Ballari, Karnataka
nagabhushancm@vskub.ac.in

2. Chromosomes are the thread like structures of NA and
proteins found in the nucleus of most of the living
organisms carrying genetic information in the form of
GENES
The definition

3. CHROMA=COLOUR
SOMA= BODY
E. STRASBURGER (1875) DISCOVERED THREAD-LIKE STRUCTURES
APPEARED DURING CELL DIVISION.
WALDEYER COINED THIS TERM (1888).
THE DETAILED CHROMOSOME IS SEEN IN THE METAPHASE WITH
SUITABLE DYES.
IN ALL EUKARYOTIC ORGANISMS DEFINITE NUMBER OF
CHROMOSOMES WITH DEFINITE SIZE AND DEFINIT SHAPE.
Chromosome

4. CHROMA=COLOUR
SOMA= BODY
E. STRASBURGER (1875) Discovered Thread-like Structures Appeared
During Cell Division.
The detailed chromosome is seen in the METAPHASE with suitable dyes.
IN ALL EUKARYOTIC ORGANISMS DEFINITE NUMBER OF
CHROMOSOMES WITH DEFINITE SIZE AND DEFINITE SHAPE.
DIPLOID IN SOMATIC CELLS; HAPLOID IN GAMETES.
Chromosome

5. AUTOSOMES:
control characters of the body other than sex
characters.
ALLOSOMES / SEX CHROMOSOMES / GONOSOMES:
Involved in sex determination.
Homogametic females and heterogametic males (human).
Heterogametic females and homogametic males (fowl).
TWO TYPES OF Chromosomes

6. DIPLOID:
Diploid cells have two homologous chromosomes
independently inherited from separate parents.
(2n where n= chromosome number)
The number of chromosomes varies in different species.
Normally all the cells of a species have the same
chromosome number.
Chromosome number

7. HUMAN 46 CHIMP 48 GOAT 60
PEA 14 DEER 68 ALLIGATOR 32
CAT 38 TIGER 38 LION 38
CATTLE 60 HOUSE FLY 12 ELEPHANT 56
DOG 78 CHICKEN 78 FRUIT FLY 8
DONKEY 62 RAT 42 TURKEY 80
HORSE 64 PIGEON 80 EMU 80
RABBIT 44 QUEEN BEE
MALE DRONE
32
16
DUCK 80
Chromosome number (2n) in a few organisms

8. SIZE:
size is measured at MITOTIC METAPHASE.
It may be as short as 0.25 micron (fungi/ birds)
30 microns (trillium plant)
Each chromosome has SHORTER p- ARM (petite) and the LONGER
q-ARM.
SHAPE:
Shape is usually observed at ANAPHASE when the position of
PRIMARY CONSTRICION (CENTROMERE) determines arms
length.
Chromosome size

9. MORPHOLOGY:
MITOTIC METAPHASE is suitable stage for morphological studies.
The chromosome morphology CHANGES during cell division.
The chromosomes are THIN, COILED, ELASTIC, THREAD-LIKE
during interphase.
BUT during MITOSIS chromosomes become HIGHLY CONDENSED.
Chromosome structure

10. MORPHOLOGY:
SATELLITE
ARM
PRIMARY CONSTRICTION
SECONDARY CONSTRICTION
TELOMERE
SISTER CHROMATIDS
Chromosome MORPHOLOGY

11. CHROMATID:
each metaphase chromosome appears to be divided into two identical
parts called CHROMATIDS.
Both the chromatids are joined together at CENTROMERE.
The chromatids SEPARATE from chromosome during MITOTIC ANAPHASE
AND ANAPHASE OF MEIOSIS-II.
2 chromatids are produced through the replication of a single chromatid during
S PHASE of INTERPHASE = sister chromatids.
Chromosome MORPHOLOGY

12. CENTROMERE:
Centromere at the primary constriction is the landmark for the
identification of the chromosome.
Centromere divides chromosome into TWO ARMS p and q.
Chromosome MORPHOLOGY

14. TELOMERE:
the ends of a chromosome are TELOMERES.
they are highly stable and telomeres of different chromosomes DONOT
FUSE.
keeps the chromosomes from making contact with any membranes.
the telomeric regions have repeated sequences of T AND G bases.
Chromosome MORPHOLOGY

16. SECONDARY CONSTRICTION:
ONE or many constrictions other than PRIMARY CONSTRICTION are
secondary constrictions.
Chromosome MORPHOLOGY

18. SATELLITE:
THE chromosome region between the SECONDARY CONSTRICTION and
nearest TELOMERE is called SATELLITE, and the chromosome that possess
this region are called SAT CHROMOSOMES.
It is a SMALL CHROMOSOMAL SEGMENT separated from the main body
of the chromosome.
Chromosome MORPHOLOGY

19. TYPES:
BASED ON THE NUMBER OF CENTROMERES AND ITS POSITION.
ACENTRIC
MONO CENTRIC
DI CENTRIC
POLYCENTRIC
ACROCENTRIC
TELOCENTRIC
SUB META CENTRIC
META CENTRIC
Chromosome MORPHOLOGY

20. Tightly packed chromosome,
Intensely stained region of the chromosome,
Consists of genetically inactive satellite sequences,
Both centromeres and telomeres are heterochromatic.
heterochromatin

21. Lightly packed form, rich in gene concentration.
Often under active transcription.
It is found both in eukaryotes and prokaryotes.
euchromatin

22. 1. Current opinion in cell biology
2. National human genome research institute.
3. Chromosome condensation and decondensation during mitosis by Wolfram Antonyn and Heinz
Neumann, Elsevier, science direct Journal.
4. Topperlearning.com
5. Chromosome organisation and dynamics during interphase mitosis by Choon-Lin-Tiang, Yan He,
Wojciench P.Pawlowski, Dept of genetics, Cornwell university, Ithaca, New York.
Acknowledgement and references

23. thank you