Designing efficacious norovirus vaccines remains a major challenge due to several factors:
(1) the extreme genetic variability within the norovirus family and within genogroups
(2) the rapid evolution of antigenically dissimilar pandemic GII.4 norovirus strains
(3) the lack of lasting immunity upon natural exposure to noroviruses in at least a proportion of the population.
Answer:
Natural selection.
Explanation:
Natural Selection:
Natural selection is the evolution's one of the basic mechanism in which phenotypic variant individuals or organisms survive or reproduce with change in the heritable traits in a population over generations. With the passage of time, this process help the organisms to adapt their environment.
So, the population A and population B organisms interbreed and produce offspring with the process of natural selection.
3 nucleotides code for a single amino acid. This group of 3 is known as a codon. If you are coding for two amino acids, you would need two codons, 3 nucleotides each, for a total of 6 nucleotides.
Endocytosis is an example of passive form of transportation which is used in the cells to move substances from one point to another. It is described as passive because the process does not require energy.
Active transport is a type of transport used for movement of particles in the cells which require energy for it to occur. The major source of energy for active transport is ATP molecules, which are hydrolyzed to release energy.<span />
