Nucleotide metabolism A. Consider a mixture of two types of cell lines that are
ID: 178717 • Letter: N
Question
Nucleotide metabolismA. Consider a mixture of two types of cell lines that are identical except that one cell line has no h thymidine kinase activi TK minus) and the other cell line is wild type (normal, TK plus In HMT medium containing Hypoxanthine, Methotrexate and Thymidine, only the TK+ cells will survive and grow. How does each of the three components of HMT medium (hypoxanthine, methotrexate and thymidine) contribute to the death of the TK- cells and the selective growth of the TK+ cells? CWhy does HMT medium kill TK- cells and allow TK cells to grow?
B.What is the pyrimidine product of ribonucleotide reductase, which does NOT have an exocyclic amino group?
Another statement:
C. Cells from a patient with Lesch-Nyhan syndrome have less than 5% of wild type HGPRTase activity (HGPR Tase). These cells are not able to survive in HMT)medium containing Hypoxanthine, Methotrexate and Thymidine. However, after treatment with the mutagen methyl methane sul fonate (MMS) to induce DNA mutations, a small fraction of these cells become HGPRTase and are able to survive in HMT medium What does each of the three components of HMT medium (h oxanthine, methotrexate and thymidine) contribute to the death of the HGPRTasel cells before MMs treatment, and the growth of the mutagenized HGPR Tase cells after MMs treatment?
Nucleotide metabolism
A. Consider a mixture of two types of cell lines that are identical except that one cell line has no h thymidine kinase activi TK minus) and the other cell line is wild type (normal, TK plus In HMT medium containing Hypoxanthine, Methotrexate and Thymidine, only the TK+ cells will survive and grow. How does each of the three components of HMT medium (hypoxanthine, methotrexate and thymidine) contribute to the death of the TK- cells and the selective growth of the TK+ cells? CWhy does HMT medium kill TK- cells and allow TK cells to grow?
B.What is the pyrimidine product of ribonucleotide reductase, which does NOT have an exocyclic amino group?
Another statement:
C. Cells from a patient with Lesch-Nyhan syndrome have less than 5% of wild type HGPRTase activity (HGPR Tase). These cells are not able to survive in HMT)medium containing Hypoxanthine, Methotrexate and Thymidine. However, after treatment with the mutagen methyl methane sul fonate (MMS) to induce DNA mutations, a small fraction of these cells become HGPRTase and are able to survive in HMT medium What does each of the three components of HMT medium (h oxanthine, methotrexate and thymidine) contribute to the death of the HGPRTasel cells before MMs treatment, and the growth of the mutagenized HGPR Tase cells after MMs treatment?
A. Consider a mixture of two types of cell lines that are identical except that one cell line has no h thymidine kinase activi TK minus) and the other cell line is wild type (normal, TK plus In HMT medium containing Hypoxanthine, Methotrexate and Thymidine, only the TK+ cells will survive and grow. How does each of the three components of HMT medium (hypoxanthine, methotrexate and thymidine) contribute to the death of the TK- cells and the selective growth of the TK+ cells? CWhy does HMT medium kill TK- cells and allow TK cells to grow?
B.What is the pyrimidine product of ribonucleotide reductase, which does NOT have an exocyclic amino group?
B.What is the pyrimidine product of ribonucleotide reductase, which does NOT have an exocyclic amino group?
Another statement:
C. Cells from a patient with Lesch-Nyhan syndrome have less than 5% of wild type HGPRTase activity (HGPR Tase). These cells are not able to survive in HMT)medium containing Hypoxanthine, Methotrexate and Thymidine. However, after treatment with the mutagen methyl methane sul fonate (MMS) to induce DNA mutations, a small fraction of these cells become HGPRTase and are able to survive in HMT medium What does each of the three components of HMT medium (h oxanthine, methotrexate and thymidine) contribute to the death of the HGPRTasel cells before MMs treatment, and the growth of the mutagenized HGPR Tase cells after MMs treatment?
Explanation / Answer
A. Hypoxanthine and thymidine are intermediates in DNA synthesis while methotrexate is an inhibitor of dihydrofolate reductase. Methotrexate thus blocks de novo DNA synthesis. This block can be overlooked if the bases hypoxanthine and thymidine are present in the medium, conditional to the presence of enzymes which can make use of them for DNA synthesis. Thus, if thymidine kinase is present, cells survive as DNA can be synthesized using these nutrients.
B.Thymine is the pyrimidine without exocyclic amino group. But thymine is acted upon by another enzyme. Thus, UDP – uridine diphosphate is used as substrate without an exocyclic amino group and also a pyrimidine.
C. Hypoxanthine in HMT medium is acted upon by HGPRTase for DNA synthesis. Thus Lesch Nyhan cells which are genetically devoid of HGPRT activity, can’t grow on HMT medium. Thus, after administering MMS, when some cells can produce HGPRT, the cells can survive.
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