Chromosomal non - disjunction responsible for all except-

Ans. is 'b' i.e., Neurofibromatosis type 1 Nondisjunctiono Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division.o There are three forms of nondisiunction:Failure of a pair of homologous chromosomes to separate in meiosis I.Failure of sister chromatids to separate during meiosis II, andFailure of sister chromatids to separate during mitosis.o Nondisjunction results in daughter cells with abnormal chromosome numbers (aneuploidy).NondisjunctionMonosomyAutosomal trisomySex chromosome aneuploidyUniparental disomyMosiacism# Tumer syndrome (45XO)# Downs syndrome - Trisomy 21# Edwards syndrome - Trisomy 18# Patau syndrome - Trisomy 13# Kleinfelter syndrome# XYY male# Pradderwilli and angleman syndrome# Pallisterkillian syndrome# Hypomelanosis of ito