DNA Structure Flashcards
Where is the source of variation in DNA found?
In the nitrogenous bases:
- Adenine (A) + guanine (G)
- Thymine (T) + Cytosine (C)
What are purines and pyrimidines?
Purines are double ringed nitrogenous bases (A and G). Pyrimidines are single ringed nitrogenous bases (C and T).
What are the important pieces of information that helped solve the mystery about the structure of DNA?
The proportion of Adenine is mostly equal to the proportion of Thymine in DNA.
The proportion of Guanine is equal to the proportion of Cytosine in DNA.
Overall, the total amount of purines is equal to the total amount of pyrimidines in an organism’s genome.
Why are the proportions of Adenine and Thymine, and Guanine and Cytosine equal to each other?
Adenine almost always pairs with Thymine in DNA, that is why they exist in equal proportions, however, Adenine also exists in RNA and pairs with Uracil (U). Adenine is slightly more than Thymine because it pairs with another base - a nucleobase - Uracil, in RNA.
Guanine and Cytosine always form pairs so therefore they are always equal to each other in DNA.
What is a DNA or RNA polymerase?
A polymerase is an enzyme that amplifies or brings out the formation of polymers like DNA or RNA to synthesize (make) new DNA or RNA.
What are the practical applications of polymerase chain reaction?
DNA cloning, medical diagnostics or forensic analysis of DNA.
Why are blue eyes considered a mutation?
A mutation of a gene that codes for blue eyes switches off or inhibits the gene that determines the amount of melanin (brown pigment) that is made in the eye.
Why is DNA replicated from 5’ to 3’ direction?
The phosphate groups in DNA are located on the 5’ of the ribose sugar. DNA replication requires the free energy of the phosphate groups and the hydroxyl group on 3’ does not have a lot of energy to power or fuel this process like the phosphate groups.
What types of bonds attach the nitrogenous base and the phosphate group to the 5-carbon sugar (ribose)?
A glycosyl bond attaches the nitrogenous base to the 1' carbon of ribose. A phosphodiester (ester bond) attaches the phosphate group to 5' carbon of the ribose.
How does X-ray diffraction determine the structure of DNA?
The DNA molecule is bombarded with X-rays, some of which are deflected by the atoms in the molecule. This diffraction can be seen on a photographic film in a pattern of light and dark lines. This pattern is then solved or interpreted using mathematics.
What did Rosalind’s diffraction pattern reveal?
DNA’s structure has a helical shape that is 2nm in diameter and one complete helical turn is 3.4 nm (every 10 nucleotides).
When did Watson and Crick develop their model of DNA?
February 28, 1953
What is complementary base pairing and why is it important?
Two different types of nitrogenous bases pair up for example, purines always bond with pyrimidines where, A (purine) pairs with T (pyrimidine) in the other strand and G (purine) pairs with C (pyrimidine) in the other strand.
Importance: to transfer and store genetic information.
What is an important consequence of the complementary base pairing rule?
If you know the sequence of one strand then you know the sequence on the complementary strand.
What explains why DNA is a highly stable molecule?
DNA is made up of many hydrogen bonds that are collectively very strong which stabilizes its structure.
