MED 1201 Lecture Notes - Down Syndrome, Chorionic Villi, Prenatal Diagnosis
20 Nov 2012
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This often occurs during anaphase (in particular, meiosis i). (concepts of genetics) Nondisjunction describes the error of separation of chromosomes, when an unequal. During oogenesis and spermatogenesis, this is the same case during either anaphase i or ii, an uneven separation may occur, resulting in an n that is not 23. When the zygote is formed, though one gamete might have the correct n, there will not be. Each chromosome contains a centromere, which has a different location depending on which chromosome. From the centromere extends two arms the shorter arm (p arm) or the longer arm (q arm). Chromosomes can either be metacentric (centromere in the middle), submetacentric (between middle and end), acrocentric (close to end), or telocentric (at end). Nomenclature e. g. 5 p21 = 5th chromosome, short arm, 21st band from the centromere (going from the centromere outward) Chromosome function carry dna in a way that facilitates distribution during mitosis.
