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Prometaphase is the phase of mitosis following prophase and preceding metaphase in eukaryotic somatic cells. In prometaphase, the nuclear membrane breaks apart into numerous "membrane vesicles," and the chromosomes inside form protein structures called kinetochores . [ 1 ]
Studies in male mouse meiosis have shown that after DNA damaging treatments like gamma irradiation, two types of repair responses occur depending on the meiotic stage: [5] From leptotene to early pachytene, exogenous DNA damage triggers widespread presence of the repair protein gammaH2AX in the nucleus, associated with homologous recombination ...
Pairing of the X and Y chromosomes and crossing over (recombination) between their pseudoautosomal regions appear to be necessary for the normal progression of male meiosis. [16] Thus, those cells in which X-Y recombination does not occur will fail to complete meiosis. Structural and/or genetic dissimilarity (due to hybridization or mutation ...
The control line of this pregnancy test is blank, making the test invalid. The control line on the left of this pregnancy test is visible, suggesting that the test result is valid. A pale purple line has also appeared on the right hand side (the test line) which clearly signifies that the subject is pregnant.
Meiosis generates genetic variation in the diploid cell, in part by the exchange of genetic information between the pairs of chromosomes after they align (recombination). Thus, on this view, [28] an advantage of meiosis is that it facilitates the generation of genomic diversity among progeny, allowing adaptation to adverse changes in the ...
The synaptonemal complex is a tripartite structure consisting of two parallel lateral regions and a central element. This "tripartite structure" is seen during the pachytene stage of the first meiotic prophase, both in males and in females during gametogenesis.
Meiosis involves two rounds of chromosome segregation and thus undergoes prophase twice, resulting in prophase I and prophase II. [12] Prophase I is the most complex phase in all of meiosis because homologous chromosomes must pair and exchange genetic information. [3]: 98 Prophase II is very similar to mitotic prophase. [12]
During meiosis, 5 of X form one chain, and 5 of Y form another chain. Thus, they behave effectively as a typical XY chromosomal system, except each of X and Y is broken into 5 parts, with the effect that recombinations occur very frequently at 4 particular points. [ 17 ]