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This is an accepted version of this page This is the latest accepted revision, reviewed on 16 February 2025. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
Meiosis undergoes two divisions resulting in four haploid daughter cells. Homologous chromosomes are separated in the first division of meiosis, such that each daughter cell has one copy of each chromosome. These chromosomes have already been replicated and have two sister chromatids which are then separated during the second division of ...
It can also happen during mitotic division, [1] which may result in loss of heterozygosity. Crossing over is important for the normal segregation of chromosomes during meiosis. [ 2 ] Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the ...
Telophase (from Ancient Greek τέλος ' end, result, completion ' and φάσις (phásis) ' appearance ') is the final stage in both meiosis and mitosis in a eukaryotic cell. During telophase, the effects of prophase and prometaphase (the nucleolus and nuclear membrane disintegrating) are reversed.
Thus on this view, the adaptive advantage of meiosis is that it facilitates recombinational repair of DNA damage that is otherwise difficult to repair, and that occurs as a result of stress, particularly oxidative stress. [19] [20] If left unrepaired, this damage would likely be lethal to gametes and inhibit production of viable progeny.
The majority of cases result from nondisjunction during maternal meiosis I. [14] Trisomy occurs in at least 0.3% of newborns and in nearly 25% of spontaneous abortions. It is the leading cause of pregnancy wastage and is the most common known cause of intellectual disability. [15]
This process results in each gamete usually containing a mixture of chromosomes from both original parents. Improper chromosome segregation (see non-disjunction, disomy) can result in aneuploid gametes having either too few or too many chromosomes. The second stage at which segregation occurs during meiosis is prophase II (see meiosis diagram ...
An exception is towards the end of meiosis, after crossing over has occurred, because sections of each sister chromatid may have been exchanged with corresponding sections of the homologous chromatids with which they are paired during meiosis. Homologous chromosomes might or might not be the same as each other because they derive from different ...