Nucleic Acids Flashcards
Name the purine bases in DNA.
Adenine and guanine.
Name the pyrimidine bases in DNA.
Thymine and cytosine.
Name the pyrimidine bases in RNA.
Uracil and cytosine.
What is the advantage of using thymine rather than uracil in DNA?
Uracil is formed by the spontaneous deamination of cytosine. If uracil is already present, repair mechanisms can’t tell which uracil residues are incorrect, so can’t fix them.
What sugar is present in RNA and DNA nucleotides? What is the difference between them?
Ribose sugar in RNA, and 2-Deoxyribose sugar in DNA. 2-Deoxyribose lacks a hydroxyl group on the 2’ carbon.
Why does the extra OH group on ribose sugar make RNA less stable?
The OH group is not involved in forming phosphodiester bonds in the backbone, so it is reactive.
Ribose + base =
Nucleoside
Ribose + base + phosphate =
Nucleotide
Which carbon are the phosphate groups attached to in nucleotides?
5’
What property do the 3’ and 5’ ends give to DNA?
Directionality.
What bonds join the complementary DNA base pairs?
Hydrogen bonds.
How many hydrogen bonds form between C and G?
3
How many hydrogen bonds form between A and T?
2
How many base pairs are in one complete turn in DNA?
10 base pairs.
DNA has two grooves, what are they?
It has a minor groove (shallow and wide) and a major groove (deep and narrow).
