Cell Division and Continuous Life Processes — NEET Biology
📚 Practice ConceptAccording to the cell theory, cells arise from preexisting cells. The process by which this occurs is called cell division. Any sexually reproducing organism starts its life cycle from a single-celled zygote. Cell division does not stop with the formation of the mature organism but continues throughout its life cycle.
Which of the following statements are correct regarding the events and outcomes of meiosis in a diploid organism (2n chromosomes, 2C DNA in G1 phase)? S1. Prior to the initiation of Meiosis I, the cell undergoes S-phase, resulting in a chromosomal complement of 2n and a DNA content of 4C. S2. Meiosis I is a reductional division where homologous chromosomes separate, leading to the formation of two haploid cells, each containing n chromosomes and 2C DNA. S3. If a cell completes Meiosis I but subsequently skips Meiosis II, the two resulting cells will each possess n chromosomes, with each chromosome still composed of two chromatids. S4. The primary outcome of skipping Meiosis II would be the formation of gametes that are haploid in chromosome number but diploid in DNA content, which upon self-fusion could lead to an organism with tetraploid DNA content (2n, 4C). S5. The process of synapsis, chiasmata formation, and crossing over occur during Meiosis I, contributing to genetic variation irrespective of Meiosis II completion.
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Correct answer: C — All statements (S1-S5) are correct
Let's evaluate each statement: S1. Correct. After the S-phase, DNA replication occurs, doubling the DNA content from 2C to 4C, while the chromosome number remains diploid (2n), with each chromosome now consisting of two sister chromatids. S2. Correct. Meiosis I is indeed a reductional division where homologous chromosomes separate. This reduces the chromosome number from 2n to n. Each resulting cell is haploid in chromosome number, but each chromosome still has two chromatids, so the DNA content is 2C. S3. Correct. If Meiosis II, which is responsible for separating sister chromatids, is skipped, the two cells formed after Meiosis I will not undergo this separation. Thus, they will remain with n chromosomes, each composed of two chromatids. S4. Correct. Cells formed after skipping Meiosis II are (n, 2C). These cells are haploid in terms of chromosome number (n) but contain twice the DNA content (2C) compared to a normal haploid gamete (1C). If two such gametes (n, 2C) fuse, the resulting zygote would have 2n chromosomes and 4C DNA, which signifies a diploid organism with tetraploid DNA content, a form of polyploidy. S5. Correct. Synapsis (zygotene), chiasmata (diplotene), and crossing over (pachytene) are all characteristic events of Prophase I. These processes generate genetic recombination and variation, which is completed before Meiosis II takes place. Therefore, all statements S1, S2, S3, S4, and S5 are correct.
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
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