how can non-disjunction lead to the production of an egg cell with an extra chromosome

Expert Answers
trophyhunter1 eNotes educator| Certified Educator

Non-disjunction is when homologous chromosomes fail to separate during meosis I or II. The result is that the unseparated chromosome pair will enter one daughter cell, while the other daughter cell will not get that chromosome at all. For example, if this were a human gamete, there would be either 22 or 24 chromosomes in the abnormal gamete. This condition is called aneuploidy.

senioreeto | Student
in non-disjunction,the homologous chromosomes fail to separate from each other after crossing over.if they will not separate,then during the telophase,when formation of daughter cells take place,the whole unseparated pair of chromosome would move in one daughter cell and there would be no chromosome entering the other daughter cell.thus,one of the two daughter cells would have an extra chomosome while the other would be left with no chromosome.