Chromosomal nomenclature

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 [email protected]

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

13. 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

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

15. 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

16. 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

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

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

19. Current opinion in cell biology National human genome research institute. Chromosome condensation and decondensation d uring mitosis by Wolfram Antonyn and Heinz Neumann, Elsevier, science direct Journal. Topperlearning.com 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

20. thank you