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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Farheen Mukadam posted an Question
April 12, 2020 • 03:46 am
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2 points
2 points
- IIT JAM
- Biotechnology (BT)
The precocity theory of synapsis proposed by darlington could not hold 2 poin (csir-ugc net, gate. jam, jrf-aice, jest) * ground because o o it clashed with the
The precocity theory of synapsis proposed by Darlington could not hold 2 poin (CSIR-UGC NET, GATE. JAM, JRF-AICE, JEST) * ground because O O It clashed with the semiconservative nature of DNA replication It claimed that crossing over takes place during DNA replication in single chromatid structures O It could not explain the attraction between homologous chromosomes O It claimed that crossing over takes place during transcription of DNA
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Narayan singh Best Answer
Chiasmatype theory was proposed by F.A. Janssens in 1909 and was extended in 1924. It was later fully developed by J. Belling and by CD. Darlington. According to this theory, true chiasmata are the direct result of crossing over so that crossing over really precedes chiasma formation. As opposed to classical theory, in chiasma type theory, crossing over results from breakage followed by reunion or exchange of non-sister chromatid segments from homologous chromosomes. Since in this theory, chiasmata are the result of crossing over, there would be one to one relationship between the chiasmata and crossing over. This theory is also called one plane theory as against two plane theory discussed above. In this theory, one would expect reductional separation of chromatids on either side of a chiasma.