Chapter 12 - DNA Flashcards
Why are hydrogen bonds effective at joining nitrogenous bases?
Hydrogen bonds are strong enough to hold the bases together but weak enough to allow the bases to separate if needed.
What are nucleotides and what are they made of?
Nucleotides join together to form strands of DNA. They are made up of a sugar, a phosphate group, and nitrogenous bases.
What does DNA polymerase do?
DNA polymerase is an enzyme that joins nucleotides to produce a new strand of DNA. It also corrects base pair errors.
What is a bacteriophage?
A bacteriophage (“bacteria eater”) is a kind of virus that infects bacteria. When it enters a bacterium, it attaches to the bacterial cell and injects its genetic information into it.
What is the role of DNA in heredity?
Its role is to store, copy, and transmit the genetic information in a cell.
Describe Griffith’s experiment.
In 1928, he isolated 2 strains (rough and smooth strain) of the same bacterial species. Only the disease-carrying S strain carried pneumonia. When he took the S strain, used heat to kill the cells, and injected a mouse with it, the mouse survived. He later mixed the killed S strain with the harmless R strain. When the mouse was injected with the mix, it developed pneumonia and died. It died due to a transformation in genes.
Describe Avery’s experiment.
Avery wanted to determine which molecule in the heat-killed bacteria was most important for transformation. When molecules of the heat-killed S-strain were mixed with an enzyme that destroys proteins, lipids, carbohydrates, and RNA, transformation still occurred. When it was mixed with an enzyme that killed DNA, transformation did not happen. This shows that DNA is the transforming factor.
Describe Hershey and Chase’s Experiment.
They wanted to determine which part of the virus (protein or DNA) entered the bacterial cell. The two men grew viruses containing two radioactive isotopes: phosphorus-32 and sulfur-35. Because proteins contain no phosphorus and DNA contains no sulfur, the scientists could now determine which molecules actually entered the bacteria. If they found radioactivity from the sulfur in the bacteria, then protein entered. If they found radioactivity from the phosphorus in the bacteria, then the DNA entered. In conclusion, the genetic material of the bacteriophage was DNA.
What are the four nitrogenous bases? What is Chargaff’s rule about them?
They are Adenine, Guanine, Thymine, and Cytosine. Chargaff’s rule states that the percent of adenine and thymine is equal in any sample of DNA. The same concept applies to cytosine and guanine.
How did Rosalind Franklin find out that there are 2 strands of nitrogenous bases?
She used X-ray diffraction.
Who took the definitive picture of DNA using x-rays?
Rosalind Franklin took the picture.
What is the function of DNA?
The main role of DNA in the cell is the storage, transmission, and copy information. It also contains the code to make proteins.
How is DNA in prokaryotic bacteria different from DNA in eukaryotes?
Prokaryotic organisms have only one chromosomes.
What is the concept of DNA being made of two strands and running in opposite directions called?
The strands of DNA are known as “antiparallel”.
What scientists devised a 3D model of the DNA’s double helix?
Watson and Crick built the double helix model.
