dna is copied
DNA is copied (for novanet cheaters)
DNA is copied in meiosis 1.
DNA is copied in meiosis 1.
DNA is copied
DNA is copied
DNA is copied (for novanet cheaters)
prophase 1.
No, crossing over occurs during prophase 1 of meiosis, not prophase 2.
Crossing over of genetic material occurs just before prophase 1 of meiosis, where homologous chromosomes exchange segments. This event does not occur before prophase 2 because homologous chromosomes have already separated during meiosis I.
Meiosis does in fact divide twice, once in meiosis I (cytokinesis) and meiosis II (cytokinesis) basically it divides into four daughter cells at the end of meiosis. Two from meiosis I and four in meiosis II
Down syndrome (trisomy 21) occurs when a gamete carrying an extra copy of chromosome 21 is involved in a fertilization event.The gamete (whether sperm or oocyte) has an extra copy of chromosome 21 because of something called NONDISJUNCTION. This happens when a chromosome gets pulled to the wrong daughter cell.This can happen either in meiosis I or meiosis II.If nondisjunction happens in meiosis I, 2 gametes will be n+1 (have the extra copy of 21) and the other 2 gametes will be n-1 (will have NO copy of 21)If nondisjunction happens in meiosis II, 2 gametes will be normal, one will be n+1 and one will be n-1.
The tetrads are pulled apart.