Explain prophase I of meosis I.(according to 5 marks)
Answers
In leptotene chromosomes are gradually visible under the microscope.
in zygotene chromosomes start pairing together n this process of association is called synapsis. n the paired chromosomes are called homologous chromosomes. the complex formed by a pair of synapsed H.C. is called a bivalent or a tetrad .
in Pachytene bivalent chromosomes now clearly appear as tetrads. this stage is characterised by the apperance of recombination nodules, the sites at which crossing over occurs between non sister chromatids of homologous chromosomes Diplotene and Diakinesis in the attachment.
hope it helped.
Answer:
Prophase of the first meiotic division has been subdivided into five phases based on chromosomal behaviour:
Explanation:
1. Leptotene: Compaction of chromosomes occurs during this phase
2. Zygotene: Chromosomes start pairing together (synapsis) to form homologous chromosomes. This is accompanied by the formation of a synaptonemal complex. The complex formed by a pair of synapsed homologous chromosomes is a bivalent/tetrad.
3. Pachytene: Recombination nodules (the sites of crossing over between non-sister chromatids of non-homologous chromosomes) appear
4. Diplotene: The synaptonemal complex is dissolved and recombined homologous chromosomes of the bivalents separate except at sites of crossovers. These sites are called chiasmata.
5. Diakinesis: Chiasmata are terminalised. Chromosomes are fully condensed again and the meiotic spindle is assembled. This is the transition to metaphase I.