1. Distinguish between somatic and reproductive cell division and explain the importance of each.
Somatic cell division, or mitosis, conserves the number of chromosome sets. It produces daughter cells that are genetically identical to their parent cell and to each other.
> Importance: enables multicellular animal or plant (gametophyte or sporophyte) to arise from a single cell; produces cells for growth, repair, and in some species, asexual reproduction; produces gametes in the gametophyte plant.
Reproductive cell division, or meiosis, reduces the number of chromosome sets from two (diploid) to one (haploid). It produces cells that differ genetically from their parent cell and from each other.
> Importance: produces gametes (in animals) or spores (in the sporophyte plant); reduces number of chromosome sets by half and introduces genetic variability among the gametes or spores.
2. What is the significance of interphase?
The mitotic phase alternates with a much longer stage called interphase, which often accounts for about 90% of the cycle. Interphase can be divided into subphases: the G1 phase (“first gap”), the S phase (“synthesis”), and the G2 phase (“second gap”). During all three subphases of interphase, a cell grows by producing proteins and cytoplasmic organelles such as mitochondria and endoplasmic reticulum. Duplication of the chromosomes, crucial division of the cell, occurs entirely during the S phase. Thus, a cell grows (G1), continues to grow as it copies its chromosomes (S), grows more as it completes preparations for cell division (G2), and divides (M). The daughter cells may then repeat the cycle.
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References:
- Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., & Jackson, R. B. (2014). Campbell Biology (10th ed.). United States of America: Pearson.