Nucleic Acids Flashcards
Which bases are purines?
adenine and guanine
Which bases are pyrimidines?
thymine, cytosine and uracil
Why are some numbers described with a prime (‘)?
Positions on the ribose ring are described with a prime (‘) to distinguish them from positions on the base ring.
What is a nucleoside?
base + sugar
What are the names of the four nucleosides?
deoxyadenosine
deoxyguanidine
deoxythymidine
deoxycytidine
What is a nucleotide?
base + sugar + phosphate
What are the names of the four nucleotides?
deoxyadenosine-5'-triphosphate = dATP deoxyguanosine-5'-triphosphate = dGTP deoxycytidine-5'-triphosphate = dCTP deoxythymidine-5'-triphosphate = dTTP
What is Chargaff’s Rule?
In DNA, the number of
A = T
G = C
Which base pair is joined by two hydrogen bonds?
A-T
Which base pair is joined by three hydrogen bonds?
G-C
What is an endonuclease?
cleaves bonds internally
What is an exonuclease?
starts at one end and cleaves bonds one at a time
What is the function of a nuclease?
cleaves phosphodiester bonds
What does EcoR1 stand for?
Eschericha coli R1
What does Pst1 stand for?
Pseudomonas stuartii 1
What does Hpa1 stand for?
Haemophilus parainfluenzae 1
What is the function of DNA ligase?
catalyses the formation of a phosphodiester link between the 5’-phosphate and 3’-OH of adjoining nucleotides in duplex DNA
What is the mechanism of ligation by DNA ligase?
- adenylation of ligase
- activation of 5’-phosphate at 5’ terminus (transfer of AMP moiety)
- displacement of AMP seals the nick
What is an example of an alkaline phosphatase?
calf intestinal phosphatase (CIP)
removes 5’-phosphate from DNA or RNA
