Nucleic Acids Flashcards
What makes up a Nucleotide?
A phosphate group,
A pentose sugar
Nitrogenous base
What is the pentose sugar in DNA?
Deoxyribose
What is the pentose sugar in RNA?
Ribose
How are polynucleotide strands formed and broken down?
Condensation reactions between nucleotides form strong phosphodiester bonds. Hydrolysis reactions use a molecule of water to break these bonds. Enzymes catalyse these reactions.
What is the structure of DNA?
Molecules twist to form a double helix of 2 deoxyribose polynucleotide strands ( so there are 2 sugar-phosphate backbones). H-bonds form between complementary base pairs (AT & GC) on strands that run antiparallel.
What are purine bases?
Adenine and Guanine
What are pyrimidine bases?
Thymine
Cytosine
Uracil
Why is DNA replication described as semi conservative?
Strands from original DNA molecule act as templates.
New DNA molecule contains 1old strand and 1 new strand (specific base pairing enables genetic material to be conserved accurately)
Was is the role of DNA helicase in semi conservative replication?
Breaks the hydrogen bonds between base pairs to form 2 single strands, each of which can act as a template.
How is a new strand formed during semi conservative replication?
Free nucleotides from nuclear sap to attach to exposed bases by complementary base pairing.
DNA polymerase joins adjacent nucleotides on new strand in a 5->3 direction via condensation reactions to form phosphodiester bonds.
Hydrogen bonds reform
What are features of the genetic code?
Non-overlapping- each triplet is only read once
Degenerate- more than one triplet codes for the same amino acid (64 possible triplets for 20 amino acids)
Universal- same bases and sequences used by all species
How does a gene determine the sequence of amino acid in a protein?
Consists of base triplets that code for a specific amino acid
How can DNA be purified by precipitation?
Add ethanol and a salt to aqueous solution. Nucleic acids precipitate out if the solution.
Centrifuge to obtain pellet of nuclei acid. Wash pellet with ethanol and centrifuge again
What does transcription produce?
mRNA
Where does transcription occur?
In the nucleus