<span>Only one sperm normally fuses
with an egg because if more than one sperm fuses, through a process
called polyspermy, development of the zygote usually stops.
</span>
<span>Fertilization of one egg by
two sperm is possible, but the resulting zygote is almost never viable
because such a zygote would have three sets of chromosomes instead of
the normal two. This condition, called triploidy, is usually
incompatible with life. Those rare triploid infants that do survive to
term have severe and multiple birth defects and rarely live more than a
few days. </span>
The answer is <span>Meiosis I.</span>
<span>Meiosis is a cell division which results in the reduction of chromosome
number by half - from diploid to haploid - in daughter cells. It consists
of meiosis I and meiosis II. Meiosis I produces two
haploid cells. Meiosis
II is analogous to mitosis, so each of these two haploid cells will in meiosis
II produce two haploid cells. In total, meiosis results in four haploid cells.</span>
<span>
</span>
<span>Therefore, the production of two haploid daughter cells is in meiosis I.</span>
Answer:b. an mRNA transcript to which multiple ribosomes are attached
Explanation: polysome consist of mRNA complex and two or more ribosome coming together to translate mRNA into a polypetide or amino acid. It helps produce many polypeptide from a single mRNA.
Different ribosomes bind to the mRNA at different time elongating the polypeptide chain. We have the free( non-poly A ) and memberane bound (poly A) polysome.
Differentiation in plants refers to the processes by which distinct cell types arise from precursor cells and become different from each other. Plants have about a dozen basic cell types that are required for everyday functioning and survival. Additional cell types are required for sexual reproduction. While the basic diversity of plant cell types is low compared to animals, these cells are strikingly different. For example, some cells such as parenchyma cells retain the potential to respond to environmental and/or hormonal signals throughout their life and, under the right conditions, can be transformed into another cell type (transdifferentiation). Other cells such as the water-conducting vessel elements undergo cell death as part of their differentiation pathway and thus can never transdifferentiate to another cell type
Read more: http://www.biologyreference.com/Co-Dn/Differentiation-in-Plants.html#ixzz54pAhWVdn
