Although meiosis typically splits sex cells into the haploid number, every once in a while it is not balanced. One sex cell gets one less, while the other gets one more chromosome. If the cell with an extra chromosome is involved in fertilization, the zygote will have an extra chromosome.
However, since this is not my area of expertise, I searched Google under the key words "'extra chromosome'" to get these possible sources:
http://en.wikipedia.org/wiki/Down_syndrome
http://www.babycenter.com/404_what-does-it-mean-when-a-baby-has-an-extra-chromosome_5279.bc
http://biology.about.com/od/basicgenetics/a/aa110504a.htm
http://hmg.oxfordjournals.org/cgi/content/full/8/12/2205
More information might be available under "trisomy."
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps. Thanks for asking.
explain how a zygote could end up with an extra chromosome
please help my book does not explain
1 answer