Answer:
Restriction enzymes (endonucleases) are used to cut the DNA into fragements.
Explanation
Restriction enzymes are obatained from bacteria where they are utilized by bacteria for protection against viruses. Restriction enzymes are used in biotechnology research. There are several restriction enzymes and each cut the DNA at specific site known as recognition site which is usually 4-8 neucleotide long. They produce sticky ends (cutting the both DNA strand on different site) and blunt ends (cutting the both DNA strand on same site) on DNA fragments.
Answer:
TCR
Explanation:
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.