Models are simplified representations of of different complex systems. They also help to study very small or large objects.
Option B, D and E.
Explanation:
Models are very simplified representations of complex systems and organs or structures which are prepared to study those systems by scientists and normal people easily. Many structures of human body like cells or some tissues are very small in structure or microscopic in nature. So studying them are very hard without specific instruments which are not always available. Thus models are made to easily study those structures by scientists and even normal people and students.
<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>
Answer:
DNA replication
Explanation:
DNA replication is the process whereby the genetic material (DNA) duplicates itself into two identical copies. This process must occur prior to any cellular division (meiosis or mitosis) in order to ascertain that each daughter cell gets an even and correct amount of DNA.
The process of DNA replication begins with the unwinding of the double stranded DNA molecule into two single strands of DNA. One strand called leading strand runs from 3'-5' while the other strand runs from 5'-3'. However, DNA replication proceeds in the 5'-3' direction.
