To create cellular factories for monoclonal antibody production, cells derived from an immortalized B lymphocyte cell line (M) are cultured together with antibody-secreting B lymphocytes (B) on a so-called HAT medium. The medium contains an inhibitor of DHFR, an enzyme essential for de novo nucleotide biosynthesis. Additionally, it contains substrates for the only alternative nucleotide biosynthetic pathway called the salvage pathway. The enzyme HGPRT is essential for the salvage pathway. One of the cells mentioned above lacks the gene encoding one of the enzymes mentioned. Considering the role of the HAT medium in selecting for hybrid cells that are both immortalized and secrete antibodies, which cell (B or M) do you think is missing an enzyme? Which enzyme is missing in this cell?
A) M - DHFR
B) M - HGPRT
C) B - DHFR
D) B - HGPRT

Question

Quizplus · Accepted Answer

The transformed myeloma (M) cells are immortalized but are not selected for in HAT media. This is because they lack HGPRT and their DHFR-dependent pathway is also inhibited. Non-fused B cells can still make their nucleotides by the salvage pathway but can only proliferate for a few generations. The hybrid cells, on the other hand, are both immortalized and capable of carrying out the salvage pathway.

To Create Cellular Factories for Monoclonal Antibody Production, Cells Derived