Why was it difficult to use DNA as evidence in a crime before PCR was invented? A. You need many copies of DNA for DNA fingerpri
nting. B. PCR is the only way to cut DNA into separate pieces. C. You need to be able to produce mRNA from DNA. D. It was impossible to copy DNA before PCR was invented.
The correct answer is option A. "You need many copies of DNA for DNA fingerprinting".
Explanation:
Polymerase chain reaction (PCR) is a method that revolutionized molecular biology for its ability to create multiple copies of DNA at specific sequences. For instance, before PCR was invented it was difficult to use DNA as evidence in a crime because many copies of DNA are needed for DNA fingerprinting, the most widely used test to match the sample with the suspect. Nowadays, thanks to PCR, a drop of blood or a hair is enough to perform a DNA fingerprinting test.
C. All cells arise form previously existing cells. This is because the scraped knee's cells would be replaced by the exact same ones that were removed. Kind of like "Out with the old and in with the new... yet the exact same..!"
Monoclonal antibodies can treat cancer as well as other illness such as the coronavirus by mimicking the body's immune system. They recognize and target specific proteins on cells. Some on cancer cells by basically blocking signals that tell cancer cells to divide.
