Answer: DNA is made up of repeating units of building blocks called nucleotides.
Explanation.
Deoxyribonucleic acid(DNA) is a long polymer made up of repeating units building blocks called nucleotides. Nucleotides is the organic building block of DNA and it consist of sub unit molecules, a nitrogenous base called nucleobase, a six carbon sugar called deoxyribose and a phosphate group. The bases use in DNA are adenine(A), cytosine(C), thymine(T) and guanine(G). Nucleotide is important for cellular metabolism.
Helper T cells are the CD4T cells that are present in the inactive form. These cells have receptors for antigens on their surface. These antigen receptors are called T-cell receptors (TCRs). The function of TCR is to recognize and bind to specific foreign antigen fragments that are presented in antigen–MHC complexes. Different helper T cells have their unique TCRs to recognize a specific antigen–MHC complex. The CD4 proteins of helper T cells also interact with the MHC antigens and help maintain the TCR–MHC coupling.
