2.3 Flashcards
Q: What is the purpose of mitosis?
- Segregation of duplicated chromosomes into daughter nuclei (karyokinesis).
- Division of the cell into two daughter cells (cytokinesis).
Q: How is cytokinesis achieved in animal cells?
It is achieved by the appearance of a furrow in the plasma membrane, which gradually deepens and divides the cell cytoplasm into two.
Q: How does cytokinesis occur in plant cells?
Plant cells undergo cytokinesis by the formation of a new cell wall.
Wall formation starts in the center of the cell and grows outward to meet the existing lateral walls.
A precursor called the cell-plate is formed, representing the middle lamella between the walls of two adjacent cells.
Q: What happens if cytokinesis is not followed after karyokinesis?
A multinucleate condition arises, leading to the formation of syncytium.
Q: What is mitosis?
Mitosis is the equational division that typically occurs in diploid cells.
Q: What is the significance of mitosis?
- Mitosis produces diploid daughter cells with identical genetic complement.
- It allows for growth in multicellular organisms by restoring the nucleo-cytoplasmic ratio.
- Mitosis plays a crucial role in cell repair, such as replacing cells in the upper layer of the epidermis, lining of the gut, and blood cells.
- Mitotic divisions in meristematic tissues, like the apical and lateral cambium, contribute to continuous growth in plants.
Q: What is meiosis?
Meiosis is a specialized type of cell division that reduces the chromosome number by half and produces haploid daughter cells.
Q: When does meiosis occur in sexually reproducing organisms?
- Meiosis involves two cycles of nuclear and cell division (meiosis I and meiosis II) but only one cycle of DNA replication.
- Meiosis I is initiated after the parental chromosomes have replicated to produce identical sister chromatids.
- Meiosis involves pairing of homologous chromosomes and recombination between non-sister chromatids.
- Four haploid cells are formed at the end of meiosis II.
Q: What are the phases of meiosis?
- Meiosis I: Prophase I, Metaphase I, Anaphase I, Telophase I.
- Meiosis II: Prophase II, Metaphase II, Anaphase II, Telophase II.
Q: What are the phases of Prophase I in meiosis?
Prophase I is divided into five phases:
* Leptotene
* Zygotene
* Pachytene
* Diplotene
* Diakinesis.
Q: What are the phases of Prophase I in meiosis?
Prophase I is divided into five phases:
* Leptotene
* Zygotene
* Pachytene
* Diplotene
* Diakinesis.
Q: What happens during Leptotene stage?
Chromosomes gradually become visible under the microscope, and compaction of chromosomes continues.
Q: What happens during Zygotene stage?
Chromosomes start pairing together through synapsis, forming homologous chromosomes. A complex structure called the synaptonemal complex is formed.
Q: What happens during Pachytene stage?
The four chromatids of each bivalent chromosome become distinct and form tetrads. Recombination nodules appear, allowing crossing over between non-sister chromatids.
Q: What happens during Diplotene stage?
The synaptonemal complex dissolves, and the recombined homologous chromosomes of the bivalents tend to separate except at the sites of crossovers.
X-shaped structures called chiasmata are formed.
