Analogs of nucleotides are often used in studies of DNA. An analog is a modification of one of the normal bases that can be incorporated into DNA via replication and can later be detected for analysis. The thymidine analog 5-ethynyl-2′-deoxyuridine (EdU) is widely used in the laboratory for these types of experiments. However, EdU is toxic to cells, and inclusion of EdU in growth medium eventually causes cell death, unlike other thymidine analogs. Recently, a research team examined if cells recognized EdU as damage to the DNA and if the cells used the nucleotide excision repair (NER) systems to fix the DNA (see figure A). Human cells cultured in the lab were treated for 24 hours with either EdU or another thymidine analog, BrdU (blue circles in the figure). The cells were then exposed to UV light where damage would occur (red triangles in the figure). After 1 h of repair in the presence of the analog, the cells were lysed and excision products were separated from cells. An anti-BrdU antibody was used to pull out (immunoprecipitate) any excision products that contained BrdU or EdU (BrdU IP- note that antibodies are depicted in figure A as ”upside-down Y’s”). These precipitated samples were analyzed through gel electrophoresis (figure B). 1. Is there experimental evidence that EdU is excised by NER and BrdU is not? Fully explain your answer, and be sure to include a discussion of why UV light was included in some of the samples. 2. Why might EdU be recognized by NER but other thymine analogs not be recognized? The researchers hypothesized that EdU could act as a chemotherapy drug. If excessive amounts of EdU were targeted to rapidly dividing tumor cells, how would this cause toxicity and effectively kill off the cancer cells? 3. If added to a culture of Salmonella in the Ames test, would EdU be identified as a mutagen? Explain your answer.
Nucleotides
It is an organic molecule made up of three basic components- a nitrogenous base, phosphate,and pentose sugar. The nucleotides are important for metabolic reactions andthe formation of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Nucleic Acids
Nucleic acids are essential biomolecules present in prokaryotic and eukaryotic cells and viruses. They carry the genetic information for the synthesis of proteins and cellular replication. The nucleic acids are of two types: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The structure of all proteins and ultimately every biomolecule and cellular component is a product of information encoded in the sequence of nucleic acids. Parts of a DNA molecule containing the information needed to synthesize a protein or an RNA are genes. Nucleic acids can store and transmit genetic information from one generation to the next, fundamental to any life form.
Analogs of nucleotides are often used in studies of DNA. An analog is a modification of one of the normal bases that can be incorporated into
Recently, a research team examined if cells recognized EdU as damage to the DNA and if the cells used the
1. Is there experimental evidence that EdU is excised by NER and BrdU is not? Fully explain your answer, and be sure to include a discussion of why UV light was included in some of the samples.
2. Why might EdU be recognized by NER but other thymine analogs not be recognized? The researchers hypothesized that EdU could act as a chemotherapy drug. If excessive amounts of EdU were targeted to rapidly dividing tumor cells, how would this cause toxicity and effectively kill off the cancer cells?
3. If added to a culture of Salmonella in the Ames test, would EdU be identified as a mutagen? Explain your answer.
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