dna Flashcards
(6 cards)
Describe the basic functions of RNA in all living cells
RNA Transfers genetic information from DNA to ribosomes
Suggest how the structure of DNA relates to its functions
● Two strands → both can act as templates for semi-conservative replication
● Hydrogen bonds between bases are weak → strands can be separated for replication
● Complementary base pairing → accurate replication
● Many hydrogen bonds between bases → stable / strong molecule
● Double helix with sugar phosphate backbone → protects bases / hydrogen bonds
● Long molecule → store lots of genetic information (that codes for polypeptides)
● Double helix (coiled) → compact
Why is semi-conservative replication important?
Ensures genetic continuity between generations of cells
Describe the process of semi-conservative DNA replication
- DNA helicase breaks hydrogen bonds between complementary bases, unwinding the double helix
- Both strands act as templates
- Free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing
- Hydrogen bonds form between adenine-thymine and guanine-cytosine
- DNA polymerase joins adjacent nucleotides on new strand by condensation reactions
- Forming phosphodiester bonds
Use your knowledge of enzyme action to suggest why DNA polymerase
moves in opposite directions along DNA strands
● DNA has antiparallel strands
● So shapes / arrangements of nucleotides on two ends are different
● DNA polymerase is an enzyme with a specific shaped active site
● So can only bind to substrate with complementary shape (phosphate end of developing strand)
Why is DNA antiparallel
- allows complementary base pairs (A-T, C-G) to form hydrogen bonds efficiently and stack properly inside the helix.
It stabilizes the structure by optimising bonding angles.
necessary for enzymes like DNA polymerase to work properly during replication, as they only add nucleotides to the 3’ end.
