<span>The answer is D. Example
of such a relationship is that of a tick and a cow. The tick is the
ectoparasite while the cow is the host.
The tick benefits by sucking blood from the cow while the cow is disadvantaged since it is losing some of its
blood and also the tick is a vector of disease</span>
Eukaryotic cells have organelle while prokaryotic cell do not have it.
The level of DNA packaging which is brought about by the formation of nucleosomes it looks like beads on a string.
In general terms, nucleosomes are termed as a basic unit of DNA packaging which is in eukaryotes.
It consists of eight segments of DNA wound. Nucleosomes form a fundamental unit which repeats the eukaryotic genomes to the nucleus by ensuring a well appropriate access to it.
The right answer is Watson and Crick.
The famous science journal "Nature" published an article of two pages, accompanied by one figure, titled "A Structure for Deoxyribose Nucleic Acid". Its authors are James Dewey Watson (24) and Francis Crick (36).
They synthesized the work of their scientific colleagues and were able to explain with a remarkable art of deduction how the DNA molecule contained in the cells of all living beings was duplicated.
