Nucleic Acids Flashcards
(30 cards)
What is the role of DNA?
Carries genetic information
What is the role of RNA?
Transfers genetic information from DNA to ribosomes
Name the monomer of a nucleic acid
nucleotide
State three components of a nucleotide
Pentose sugar, nitrogen containing base, and phosphate group
State the five bases of a nucleotide?
Adenine, guanine, thymine, cytosine and uracil
What is a pentose sugar?
Sugar containing five carbons
What is the pentose sugar in DNA and RNA?
DNA- Deoxyribose
RNA- Ribose
What sort of reaction combines two nucleotides?
Condensation reaction
What bond is formed when two nucleotides combine?
Phosphodiester bond
Describe the structure of DNA
Double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs
How is the structure of DNA related to its functions?
- Stable structure which can pass from generation to generation without change
- Two separate strands (both strands act as template strands) joined by hydrogen bonds for replication
- Large so carries a lot of genetic info
- Genetic info protected by sugar phosphate backbone.
Describe the structure of RNA
Relatively short polynucleotide chain
What are three differences between RNA and DNA?
- DNA is double stranded RNA single
- DNA has deoxyribose, RNA ribose
- DNA has thymine, RNA has uracil
How does complementary base pairing allow us to work out the frequency of relative bases?
Knowing the frequency of a base will indicate the frequency of its complementary pair
State the mechanism of DNA replicaiton
Semi-conservative
Describe semi-conservative replication?
DNA helicase separates the two strands. Free nucleotides bond to their complementary bases. They are joined by DNA polymerase which makes phosphodiester bonds.
Why is semi-conservative replication important in the genetic continuity between cells?
Half is preserved so there will always be a strand of former DNA so genetic continuity is ensured between generations.
State the enzymes involved in DNA replication
DNA helicase and DNA polymerase
What does DNA helicase do?
Unwinds double helix and breaks hydrogen bonds.
What does DNA polymerase do?
Catalyses the condensation reaction creating phosphodiester bonds between nucleotides. This forms the sugar phosphate backbone.
The two strands of the double helix are {} to each other in terms of direction.
Antiparallel
What are the new strands of DNA formed from?
Free nucletides
How was semi conservative replication proven true?
DNA was marked with a heavy nitrogen isotope. It was then replicated using a light nitrogen isotope. The mass of the DNA was determined by which isotopes it contained.
The results showed that DNA strands were separating and forming a new strand each generation.
Parent DNA- heavy nitrogen isotope
1st generation- half heavy half light
2nd generation- either half and half or entirely light.
Why is ATP a suitable energy source for cells?
Releases manageable amounts of energy.
Phosphorylates other compounds making them more reactive.
Can be rapidly re-synthesised.
