I would say C.nervous system because that pretty much defines all of the answer choices.
The correct answer is protein.
Proteins are macromolecules composed of amino acids with the wide range of structures. Protein functions are diverse:
• structural proteins-maintaining the cell shape, (for example, proteins are structural elements in connective tissues like cartilage and bone in vertebrates),
• Enzymes - catalyze the biochemical reactions in cells-.
• Monitors- changing their activity in response to metabolic signals
• Part of the extracellular matrix or involved in intercellular communication…
The process of RNA editing is the alteration of the sequence of nucleotides in the RNA after it has been transcribed from DNA, but before it is translated into a protein. RNA editing occurs by two distinct mechanisms:<em><u /><u>Substitution</u> <u>editing </u></em>and <u><em>Insertion/</em></u><em></em><u><em>deletion</em></u><em> <u>editing</u></em>.
<u><em>Substitution editing</em></u> is the chemical alteration of individual nucleotides. These alterations are catalyzed by enzymes that recognize a specific target sequence of nucleotides:
*Cytidine Deaminases that convert a C in the RNA to uracil.
*<em />adenosine deaminases that convert an A to inosine,which the ribosome translates as a G.<span>Thus a CAG codon</span><span> (for Gln) can be converted to a CGG codon (for Arg).
<em><u>*Insertion/deletion editing</u></em><em><u /></em><u /> is the insertion or deletion of nucleotides in an RNA.
These alterations are mediated by guide RNA molecules that base-pair as best they can with the RNA to be edited and serve as a template for the addition( or removal) in the target.</span>
In recent molecular genetic studies, genes associated with the neurotransmitter Dopamine have been linked to ADHD.
ADHD stands for Attention Deficit Hyperactivity Disorder. People with ADHD have a hard time focusing on tasks. Scientists have found that the low levels of dopamine in the brain are associated with the symptoms of ADHD. It is because the neurons in the brain have a high amount of protein called the dopamine transporters. These proteins block the dopamine from passing between the neurons. This decreases the effect of dopamine.
