This discussion has been closed.
Posted by bitesizebiologyteacher (U15169682) on Saturday, 10th November 2012
Here's a question. See if you can answer it and post your answer. I'll be back tomorrow to help.
Explain fully how non-disjunction occurs and give at least one example.
Posted by bitesizebiologyteacher (U15169682) on Sunday, 11th November 2012
Here's the answer -
Non-disjunction occurs during Meiosis. It happens because a spindle fibre fails and one pair of chromosomes fail to separate. It results in two of the four gametes having one extra chromosome. and the other two having one too few.
An example of this is where a gamete ends up with an extra chromosome 21. If it is involved in fertilisation the zygote will have 3 chromosome 21's instead of a pair. This mutation results in Down's syndrome.
If you need any more detailed explanation of any part of this, post a question.