Explanation: The crossing over of homologous chromosomes occurs in prophase I of meiosis. Prophase I of meiosis is characterized by the lining up of homologous chromosomes close together to form a structure known as a tetrad. A tetrad is composed of four chromatids.
What happens in the prophase I?
During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. Chromosomal condensation allows these to be viewed in the microscope.
What happens to the cell during prophase 1?
Prophase I: The starting cell is diploid, 2n = 4. Homologous chromosomes pair up and exchange fragments in the process of crossing over. Metaphase I: Homologue pairs line up at the metaphase plate. Anaphase I: Homologues separate to opposite ends of the cell.
What mainly happens in prophase I in meiosis?
During prophase I, the pairs of homologous chromosomes come together to form a tetrad or bivalent, which contains four chromatids. Recombination can occur between any two chromatids within this tetrad structure.
What is the prophase 1 of mitosis?
Prophase 1 is essentially the crossing over and recombination of genetic material between non sister chromatids – this results in the genetically unidentical, haploid daughter chromatid cells.
What happens during the Prometaphase?
During prometaphase, the physical barrier that encloses the nucleus, called the nuclear envelope, breaks down. The breakdown of the nuclear envelope frees the sister chromatids from the nucleus, which is necessary for separating the nuclear material into two cells.
What are the stages of prophase 1?
Gametogenesis, Fertilization and Early Development
Meiotic prophase I is subdivided into five stages: leptotene, zygotene, pachytene, diplotene, and diakinesis.
What is prophase in cell cycle?
Prophase is the first phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. During prophase, the complex of DNA and proteins contained in the nucleus, known as chromatin, condenses.
What happens during prophase 1 and prophase 2 that is not the same?
Prophase 1 is the initial phase of meiosis 1 and prophase 2 is the initial phase of meiosis 2. … The main difference between prophase 1 and 2 is that genetic recombination occurs through crossing overs and the “Chiasmata” formation during prophase 1 whereas no genetic recombination is noticed at the prophase 2.
How is prophase I in meiosis different from prophase in mitosis?
During prophase I, the chromosomes condense, as in mitosis. However, the homologous chromosomes also pair in prophase I. … Unlike in mitosis, the sister chromosomes stay together through meiosis I, but the homologous chromosomes are separated. Each homologous chromosome carries different alleles for each gene.
What happens in prophase 1 of meiosis that results in genetic variability in a population?
Genetic variation is increased by meiosis
Recombination or crossing over occurs during prophase I. Homologous chromosomes – 1 inherited from each parent – pair along their lengths, gene by gene. Breaks occur along the chromosomes, and they rejoin, trading some of their genes.
What happens in prophase II?
During prophase II, the chromosomes condense, and a new set of spindle fibers forms. The chromosomes begin moving toward the equator of the cell. During metaphase II, the centromeres of the paired chromatids align along the equatorial plate in both cells.