Jain Biology

Author(s): Jethalal S Zaveri, Mahendramuni
Publisher: Jain Vishva Bharati

Page 47

Thus each gamete contains only one or the other member of two homologous chromosomes and never both together.
iv. The haploid nucleus may contain all paternal chromosomes or all maternal chromosomes or a mixture of both. In the last case, there is a shuffling of paternal and maternal chromosomes.
v. Due to crossing over, each chromatid (which becomes a chromosome) is a mixed chromatid containing a segment of the other chromatid.
Significance of Meiosis:
i. Haploid number of chromosomes resulting from meiosis ensures the diploid number in the zygote and subsequent vegetative cells. Hence a constancy in the number of chromosomes is maintained in the species.
ii. Meiosis induces a very large number of variations, firstly by assortment of maternal and paternal chromosomes and secondly by cross-over. This is one of the ways by which variations are produced. Variations are the raw materials for evolution.
REPRODUCTION IN PLANTS
In Botany, reproduction is generally referred to as propagation. The principal methods of reproduction in plants are also asexual and sexual as in animals.
Asexual Reproduction :
In plants, asexual propagation involves reproduction from vegetative parts of plants and is possible because the vegetative organs of many plants have the capacity for regeneration. Stem cuttings have the ability to form adventitious roots. Root cuttings can regenerate a new shoot system. Leaves can regenerate both new roots and new shoots. A stem and a root (or two stems) can be grafted together to form a continuous vascular connection and a new plant. In short, a new plant can start from a single cell. Any living cell of the plant appears to have all genetic information needed to regenerate the complete organism so that the new
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JAIN BIOLOGY