Principles of Inheritance and Variation

Chromosomal disorders-Down's syndrome, Turner's and Klinefelter's syndromes

  • These disorders are due to absence (or) excess of one (or) more characters which are non-heritable and cant be traced in pedigree chart.
  • Down's syndrome (Trisomy – 21) due to nondisjunction during oogenesis in which there will be an extra-21st chromosome, which is Characterised by rounded face, permanently open mouth, broad palm with palmer urease and congenital heart disease.
  • Turners syndrome (monosomy-x), individual has (2n = 45) one less × chromosome it will affect only Females and they will be sterile, with undeveloped breast, small uterus and rudimentary ovaries.(44 ± Yo combination of males is unviable)
  • Klinefelter's syndrome (Trisomy – X) creates sterile males, with long limbs, pitched voice and enlarged breast (gynaecomastia)

Watch this video for the topic from 0:09 to 11:43

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