Question

Why tetrads do not form during mitosis? This might be more of a conceptual question than just a simple answer of " because meiosis only happens in sex chromosomes and tetrads only form during meiosis " or " because the synaptonemal protein complex attaches the tetrads during meiosis" Another way of asking my question would be " how can we explain in detail what causes a cell to undergo meiosis vs mitosis OTHER THAN HAPPENING IN AUTOSOMAL VS SEX CHROMOSOMES?

Thank you!

Answer 1

The cells do not simply undergo mitosis or meiosis based upon the ploidy of chromosomes present in them. A very complex battery of molecular mechanisms exists behind the decision whether a cell undergoes haploid or diploid division.

The cells contain different type of division proteins, one of which are recombination proteins. The presence of these poroteins over correct location of cell and during the correct time, i.e. when the chromosomes have duplicated, results in formation of a synaptic complex. This synaptic complex, along with the presence of cyclin dependent kinases undergoes physical recombination and consequently meiosis. Hence, the optimized presence of each of the division proteins as well as their orientation as well as activation determines the nature of cellular division.