Answer:
Nitrogenous bases contain the genetic information, their amount is variable among different species, and the arrangement of these bases is also variable among different species
Explanation:
Both Watson-Crick and Pauling's DNA models considered that DNA nitrogenous bases (i.e., Adenine, Cytosine, Thymine and Guanine) contain the genetic information that determines the characteristics of living organisms. Moreover, both DNA models also considered that nitrogenous base composition varies between species, as well as the arrangement of these bases in the DNA chain also varies between species. Based on these features, Linus Pauling considered that a model where nitrogenous bases would be arranged on the outside of the DNA molecule would be easier for the DNA molecule to be replicated, transcribed, or repaired. Although incorrect, Pauling's DNA triple helix model was fundamental to develop the helical (double-stranded) structure of DNA, which was finally discovered by Watson and Crick in 1953.
<span>Cytotoxic t-cell subpopulations are specialized to combat intracellular pathogens, whereas helper t-cell subpopulations are specialized to combat extracellular pathogens.
</span>Cytotoxic t-cell are CD8+ cells. Cytotoxic t-cell uses granzymes to <span>kill </span><span>intracellular bacteria, that lives in the cytosol such as viruses. They identify the pathogen forgein peptids that are bounded to MHC-I on the cell surface.
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cd4+ T helper (Th) cells include Th1, Th2, and Th17 cells. They contribute to aliergic reactions and fighting extracellular parasites.
Answer:
C
Explanation:
Humans are the most evolved species in the phylogeny
Phylogeny in biology pertains to the evolutionary history or development of a group of organisms, such as a tribe or a racial group.
Human happen to be at the top of this evolutionary history
