Nucleic acids Flashcards
What do nucleic acids consist of?
A nitrogenous base, a phosphate and a sugar
How is the phosphate attached to the sugar?
A phosphoester bond
What is the difference between ribose and deoxyribose?
Ribose = OH on Carbon 2 Deoxyribose= H on Carbon 2
What is the structure of a purine?
Double ring
Which of the bases are purine?
Adenine and Guanine (pure agony)
What is the structure of pyrimidines?
Single ring structure
Which of the bases are pyrimidine?
Cytosine thymine and uracil
What are phosphates linked to deoxyribose sugars by?
Phosphodiester bonds
Which carbons does the phosphodiester bond form between?
3’-5’
What are the bases in each pair linked by?
Hydrogen bonds
What is the name given to describe the two chains which run in opposite directions?
Antiparallel
How many hydrogen bonds exist between Guanine and cytosine?
3
How many hydrogen bonds exist between adenine and thymine?
2
How can mRNA form base pairs
By looping back on itself
How many regions does tRNA have where base pairing is possible?
5
Where do polymerase enzymes add nucleotides to
The 3’ end of a nucleotide
What shape is formed during DNA replication?
A replication fork
What direction is the leading strand competed in?
The 5’ to 3’ direction
What does replication begin with?
An RNA primer (replaced with DNA later)
What does DNA polymerase do with respect to the primer?
Adds a new DNA nucleotide to the 3’ end and so starts to build the new DNA chain
What happens to the free nucleotides?
DNA polymerase matches them to their complementary bases on the template strand of DNA
What does DNA polymerase catalyse?
The formation of phosphodiester bonds between the end of the growing strand and the new nucleotides.
How is the phosphodiester bond formed?
When the OH of the 5’ phosphate and the OH of the 3’ deoxyribose are involved in a condensation reaction.
What is the lagging strand made in?
Short 5’-3’ fragments
What does DNA ligase do?
Links the 5’ to 3’ fragments of the lagging strand together by catalysing the formation of phosphodiester bonds between the nucleotides at the end of the fragments
