How are non-disjunction errors corrected in meiosis?

Non-disjunction errors in meiosis are not corrected; they result in gametes with an abnormal number of chromosomes.

Non-disjunction is a process that occurs during meiosis, the type of cell division that produces gametes (sperm and egg cells) for sexual reproduction. In a normal meiosis, chromosomes are supposed to separate evenly into two daughter cells. However, non-disjunction is an error in which the chromosomes do not separate properly, leading to one cell receiving an extra chromosome and the other cell receiving one less.

Unfortunately, there is no mechanism in place to correct non-disjunction errors once they have occurred. This is because by the time the error is detected, the cell has usually already completed meiosis and formed a gamete. As a result, the gamete will have an abnormal number of chromosomes, which can lead to genetic disorders if it is involved in fertilisation. For example, Down's syndrome is caused by an extra copy of chromosome 21, which is often the result of non-disjunction.

The body does have mechanisms to prevent non-disjunction from occurring in the first place. For instance, the spindle fibres that pull the chromosomes apart during meiosis are usually very accurate. Additionally, cells have a checkpoint system in place to ensure that all chromosomes are properly aligned before they are separated. However, these systems are not perfect and errors can still occur.

In some cases, organisms can survive with an abnormal number of chromosomes due to a phenomenon known as dosage compensation. This is a mechanism that balances the expression of genes between males and females and between individuals with different numbers of chromosomes. However, this is not a correction of the non-disjunction error, but rather a way for the organism to cope with the consequences.

In conclusion, while the body has mechanisms to prevent non-disjunction, there is no way to correct these errors once they have occurred. The resulting gametes will have an abnormal number of chromosomes, which can lead to genetic disorders if they are involved in fertilisation.