Dideoxynucleotides have no OH group on the sugar of the nucleotides, only H's. That means phosphate groups can't react with the sugar to form a phosphodiester bond to join two nucleotides together, so DNA syntheses is terminated
To create radioactively labeled DNA, the molecule that must be labeled is a nucleotide. Specifically, one of the nucleotides (adenine, thymine, cytosine, or guanine) can be modified to include a radioactive isotope, such as phosphorus-32 or tritium. When these labeled nucleotides are incorporated into a DNA strand during replication or synthesis, the entire DNA molecule becomes radioactively labeled. This technique is often used in molecular biology for various applications, including tracking DNA synthesis and conducting hybridization experiments.
Radioactive nucleotide
DNA polymerase
Scintillation counter
A radioactively labeled probe is made by attaching a radioactive isotope to a nucleic acid molecule, such as DNA or RNA, which is complementary to the target sequence of interest. This is typically done by incorporating the radioactive nucleotide during the synthesis of the probe or by labeling the probe post-synthesis through various chemical methods. The choice of isotope, such as phosphorus-32 or sulfur-35, depends on the specific application and detection requirements. After labeling, the probe can be used in techniques like hybridization to detect specific nucleic acid sequences in various biological samples.
The reaction that is commonly used to radioactively label DNA is the nick translation method, where a DNA molecule is treated with a DNA polymerase, dNTPs (including radioactive ones), and a DNAase to create radioactive labeled DNA fragments.
scintillation counter. APEX
Geiger Counter
The DNA separated into two classes: labeled DNA and unlabeled DNA. The labeled DNA contains the radioactively labeled nucleotides that were incorporated during DNA replication, while the unlabeled DNA represents the original, non-radioactively labeled DNA from the bacteria. The centrifugation process separated the DNA based on density, with the heavier labeled DNA migrating to a higher position in the centrifuge tube compared to the unlabeled DNA.
ER golgi vesicles that fuse with plasma membrane
Study the inheritance of traits that are not seen as a phenotype
Radioactively tagged bacteriophages are used to confirm that DNA, not protein, is injected into host cells during infection. The radioactively labeled DNA can be detected inside the host cells after infection, providing evidence that DNA is the genetic material transferred by the bacteriophages. This experiment was crucial in establishing DNA as the genetic material in organisms.