<span>. Messenger RNA (mRNA) is
synthesized from a gene segment of DNA which ultimately contains the
information on the primary sequence of amino acids in a protein to be
synthesized. The genetic code as translated is for m-RNA not DNA.
The messenger RNA carries the code into the cytoplasm where protein
synthesis occurs. The cell does
not contain large quantities of mRNA. This is because mRNA, unlike other RNAs
is constantly undergoing breakdown.
2. In
the cytoplasm, ribsomal RNA (rRNA) and protein combine to form a
nucleoprotein called a ribosome. The ribosome serves as the site and
carries the enzymes necessary for protein synthesis. The ribosome attaches
itself to m-RNA and provides the stabilizing structure to hold all substances
in position as the protein is synthesized. Several ribosomes may be attached to
a single RNA at any time. </span>
<span>
3. Transfer
RNA (tRNA) contains about 75 nucleotides, three of which are called
anticodons, and one amino acid. The tRNA reads the code and carries the
amino acid to be incorporated into the developing protein. Part of the
tRNA doubles back upon itself to form several double helical sections. The
tRNA "reads" the mRNA codon by using its own anticodon. The actual
"reading" is done by matching the base pairs through hydrogen bonding
following the base pairing principle. Each codon is "read" by various
tRNA's until the appropriate match of the anticodon with the codon occurs.</span>
Barometer measures wind speed
<span>It is well known that the centrosome acts as a microtubule organizing center, with its textbook role in forming mitotic spindles in dividing cells. So in many cells, the centrosome with its centrioles is indeed essential to ensure correct cell division, and in these the PCM ensures the distribution of the right number of centrioles to each daughter cell. But there are exceptions – which include somatic cells in fruit flies and some fungi – where no centrioles are needed; and centrosomes in some differentiated cells, including neurons and muscle cells, are inactive.</span>
Answer:
Immediately, the pathogen has been recognized:
Macrophages acts as the first line of defence by engulfing pathogens identified by antigens which will now present the antibody shape to a helper T cell.
The Helper T cells produce a signal to plasma and Memory B cells to yield antibodies that attach to the antigens. The cytotoxic cells that leads to cell death are activated by the helper T cells.
Antibodies helps to immobilize pathogen for macrophage to feed on.
if the pathogen comes back a 2nd time the memory cells helps in quick and efficient recovery by producing the specific B and T cells for the antigen.
