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Chromosomes Types

Chromosomes Types

Chromosomes Types

  1. 1. C GENETICSNAME: Rana Farrukh Hamid ROLL NO: 15101560-036 PRESENTATION TOPIC: TYPES OF CHROMOSOMES + KARYOTYPE/IDIOGRAM SUBMIT TO: …………………………..
  2. 2. TYPES OF CHROMOSOMES There are four basic types of chromosomes seen during anaphase. These are: 1.TELOCENTRIC: –No P arm, centromere is on the end 2. ACROCENTRIC: –very small P arm, centromere is very near to the end 3. SUB-METACENTRIC: –P arm just a little smaller than Q arm; centromere is in the middle 4. METACENTRIC: P and q arms are exactly the same length, centromere is in exact middle of chromosome
  3. 3. • CHROMOSOME PARTS: • Telomeres: – chromosome tips – Repeats – Important in replication, protect from diffusion with other chromosomes • Centromeres: – Highly condensed, middle region – Also repetitive sequence – Region where spindle fibers attach – Pulling chromatids apart during mitosis – Monocentric and Polycentric • Chromomeres: –during first phase (pachytene) of meiosis – bead like structures called chromomeres. • Satellite chromosomes: – chromosomes that have satellite region and secondary constriction
  4. 4. KARYOTYPE OR IDIOGRAM • It is the pictorial arrangement of total chromosomes of a cell according to their size during metaphase of cell division. • The diagrammatic representation of a chromosome complement or karyotype is called karyogram or idiogram • PREPERATION OF KARYOTYPE (TECHNIQUE): When nuclei are in metaphase of mitosis it is easy to count and characterize them. A photograph of the entire set of chromosomes can be made and pictures of individual chromosomes can be cut out and pasted in an orderly arrangement. Such a photograph reveals the number, shapes, and sizes of chromosome in a cell which constitutes its karyotype.
  5. 5. Before arrangement After arrangement
  6. 6. • A karyotype may be symmetrical or asymmetrical. A perfectly symmetrical karyotype has all metacentric chromosomes of the same size. They are known to be the primitive state from which more advanced asymmetrical karyotype have evolved through structural changes.
  7. 7. • APPLICATIONS OF KARYOTYPE: • Detection of chromosomal aberrations such as deletion, duplication, and translocation • Loss of chromosome or addition of chromosome • determine the risk of the individual and his future generations with such chromosomal variations

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