hi everyone
a question

During the first meiotic division of human oogenesis non disjunction occurs between a pair of homologous chromosomes. If fertilization occurs, which of the following is the possible number of chromosomes contributed by the female pronucleus?

(1) 21 or 23
(2) 21 or 25
(3) 22 or 23
(4) 22 or 24
(5) 23 or 24

Please answer with an explanation
thanks

Its #4.....
its on pg. 88 of First Aid 2010....

hi there....this is how i think you should solve this problem:

first of all, you should think that the gamets cell(sperm and oocytes) contain only 23 chromosomes(they are haploid; the vast majority of the cells in the body are diploid, aka contain 46 chromozomi but are 23 pairs, which mean you got one pair from 1 to 23 from father and the other pair from 1 to 23 from mother); when you produce gamets, logic you will 'pass' further to your kid only 23 chromosomes(aka one pair from 1 to 23); innitialy the cell which will finally produce gamets has, just like the other cells in the body, 46 chromosomes; normally this cell should split this 46 chromosomes exactly in 2 and give rise to 2 daughter cells with 23 chromosomes each; if, by any cause, this process of splitting is not working proparly(meiotic nondisjunction), the splitting process is wrong; the most common error is when 1 chromosome does not split(very rare when 2, 3 or more)....that means the daugter cells which should have each 23 chromosomes, will inherited a different number....the number depend very much if that chromosomes which did not split will 'go' or not in a daughet cell....if is present, that daughter cell will have 24 chromosomes and if not the daughter cell will have 22.....this is the most likely answer= option D...answer B is another option but is much rare because 21 and 25 chromosomes means 2 chromosomes did not split(again this is much rare comparing to answer D)