Practice free Cell cycle and Cell Divisions (Botany) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
DNA replication occurs:
The NCERT states, 'Meiosis involves two sequential cycles of nuclear and cell division called meiosis I and meiosis II but only a single cycle of DNA replication.' and 'Meiosis I is initiated after the parental chromosomes have replicated to produce identical sister chromatids at the S phase.'
The primary outcome of Meiosis II is to:
Meiosis I reduces the chromosome number. Meiosis II, being similar to mitosis, separates sister chromatids. Since the cells entering Meiosis II are already haploid (with duplicated chromosomes), separating the sister chromatids results in truly haploid cells with unduplicated chromosomes. Crossing over occurs in Meiosis I.
If a plant's sporophyte generation has $2n = 20$ chromosomes, how many chromosomes will be present in each cell after Meiosis II?
Meiosis reduces the chromosome number by half. If the diploid sporophyte has $2n=20$ chromosomes, the haploid cells produced after Meiosis II will each have $n=10$ chromosomes.
Which of the following phases of Meiosis II is characterized by the disappearance of the nuclear membrane and nucleolus?
While not explicitly detailed for Meiosis II, similar to Prophase I and mitotic prophase, the nuclear membrane and nucleolus disappear during Prophase II to allow for spindle fiber formation and chromosome movement.
Which of the following events during meiosis is primarily responsible for increasing genetic variability in a population?
The context states: 'It also increases the genetic variability in the population of organisms from one generation to the next. Variations are very important for the process of evolution.' and earlier mentions 'Meiosis involves pairing of homologous chromosomes and recombination between non-sister chromatids of homologous chromosomes.' Crossing over (recombination) directly leads to new combinations of alleles on chromosomes, thus increasing genetic variability.
Meiosis is essential for sexually reproducing organisms because it:
The NCERT text explicitly states: 'Meiosis is the mechanism by which conservation of specific chromosome number of each species is achieved across generations in sexually reproducing organisms, even though the process, per se, paradoxically, results in reduction of chromosome number by half.'
If a diploid cell has $2n = 46$ chromosomes, how many chromosomes will be present in a gamete produced after meiosis?
The text states: 'This specialised kind of cell division that reduces the chromosome number by half results in the production of haploid daughter cells.' If $2n = 46$, then the haploid number ($n$) would be $46/2 = 23$ chromosomes in the gametes.
Which of the following is a key characteristic exclusive to meiosis when compared to mitosis?
The context highlights: 'Meiosis involves pairing of homologous chromosomes and recombination between non-sister chromatids of homologous chromosomes.' While mitosis also has a single cycle of DNA replication (before M phase), spindle formation, and karyokinesis/cytokinesis, the pairing of homologous chromosomes (synapsis) is a defining feature of Meiosis I.
In the life cycle of sexually reproducing organisms, meiosis ensures the production of the haploid phase, while the diploid phase is restored by:
The NCERT text explicitly states: 'Meiosis ensures the production of haploid phase in the life cycle of sexually reproducing organisms whereas fertilisation restores the diploid phase.'
A megaspore mother cell (MMC) undergoes meiotic division to produce:
The context mentions: 'The MMC undergoes meiotic division... Meiosis results in the production of four megaspores (Figure 1.8a). In a majority of flowering plants, one of the megaspores is functional while the other three degenerate.'
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