Prokaryotic cells do not have a nucleus.
Answer:
Defense against a particular antigen is provided by adaptive immunity which is also called specific immunity. In adaptive immunity immunological memory is created which is used by immune cells to destroy that particular pathogen when it again comes in the body.
Adaptive immunity involves T cells and B cells. T cells generate cell mediated immune response and B cells generate a humoral immune response. These responses by T and B cells are specific to a particular pathogen which results in the killing of the pathogen by their phagocytosis enhanced by antibodies or by direct killing of pathogen.
Therefore adaptive immunity provides defense to the body against a particular pathogen by generating immunological memory.
Answer:
for example down syndrome or trisomy 21 is a common genetic disorder that occurs when a person has 3 copies of chromosome 21 there are many other promotional abnormality is including tunnel syndrome klinefelter syndrome
I think the answer is The first sentence and until the molecules in the third sentence.
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