In meiosis, the reduction in chromosome number occurs in which division?
A. Meiosis I
B. Both meiosis I and II equally
C. Only during interphase before meiosis I
D. Meiosis II
Answer: Option A
Solution (By JKSSB Mock Tests)
Meiosis I is the reductional division where homologous chromosomes separate, reducing the chromosome number from diploid (2n) to haploid (n). Meiosis II is equational division, similar to mitosis, separating sister chromatids. Thus, reduction occurs in anaphase I. DNA replication occurs in S phase before meiosis I. Gametes are haploid. Errors in reduction can lead to aneuploidy.
Explanation:
Robert Brown, a Scottish botanist, first described the nucleus in 1831 while studying epidermal cells of orchids. Hooke discovered cells, Leeuwenhoek observed living cells, Virchow proposed that cells arise from pre-existing cells. Brown's discovery was pivotal for understanding cellular organization.
Explanation:
Root pressure is the positive hydrostatic pressure developing in the xylem of roots due to active transport of ions into the vascular cylinder, drawing water osmotically. It can cause guttation in some plants. Transpiration pull is the main driving force for water ascent. Turgor pressure is the pressure of cell contents against the cell wall.
Explanation:
Neurotensin is a 13-amino acid peptide that functions as both a neuromodulator in the central nervous system and a hormone in the gastrointestinal tract. In the gut, it is secreted by the N cells in the ileum in response to fat ingestion. Its primary gastrointestinal functions are to inhibit gastric motility and gastric acid secretion (contributing to the 'ileal brake'), and to stimulate the release of histamine from mast cells and glucagon from the pancreas. It also causes vasodilation in the intestinal mucosa.
No comments yet. Be the first to start the discussion!