ladybug
Forum Senior
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Duringt he first meiotic division of human oogenesis, nondisjunction occurs between a pair of homologous chromosomes, if fertilization occurs whihc of the ff is the possible number of chromosomes contributed by the female pronucleus?
a. 21 or 23,
b. 21 or 25
c. 22 or 23
d. 22 or 24
e. 23 or 24
and why???
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| robin082006
Forum Hero
Topics: 471
Posts: 5,125
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D?
Normally a gamete has 23 chromosome. If nondisjunction occurs during the first anaphase of meiosis of oogenesis, 2 gametes have 22, 2 have 24 chromosomes.
If nondisjunction occurs during the second anaphase of meiosis of oogenesis, 2 gametes have 23, 1 gamete has 22, and 1 gamete has 24.
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| DrVirgo
Forum Hero
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I think that makes sense. 
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| waqastariq
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nice explanation
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| docarchana
Forum Guru
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excellent robin. thanku..
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| Addicudo
Forum Guru
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Buddy .. Need an Explanation for this one .. I know Non Dysjunction ... in Meiosis ONE and Two ... non dysjunction .. ! But some how aint able to make a good picture of this one here .. Robin .. Thankzz !!
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| neuroblast
Forum Newbie
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There is an excelent pic in Langman's embryo on pg 8.
Nondisjunction can occur either during the first meiotic division or the second meiotic division. If you look at the pic. the pattern of distribution is slightly varied in each set of duaghter cells but it will always be either 22 or 24, it's a really nice diagram.
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