Define DNA replication
Semi-conservative process of the production of identical strands of DNA.
Which 2 enzymes are involved in DNA replication?
DNA helicase
- Catalyses the breaking of hydrogen bonds between base pairs and the untwisting of the DNA helix
DNA polymerase
- Catalyses the formation of phosphodiester bonds between nucleotides in the new DNA strand
Describe the process of semi conservative DNA replication.
- DNA helicase catalyses the splitting of hydrogen bonds and unwinding of the double helix structure
- The 2 separate polynucleotide chains have exposed bases
- Free nucleotide pairs complementarily bond to form hydrogen bonds
- DNA polymerase catalyses the condensation of the new nucleotides to form phosphodiester bonds
- The enzyme also chekcs if the base pairing is correct
- The new molecule twists to form a double helix
Define mutation.
Occurs during replication error when the bases are not correctly matched leading to a new strand of DNA, this occurrence is spontaneous.
Define genetic code.
Sequence of bases in DNA which are instructions for amino acid production for proteins.
Where is the genetic code found in DNA?
In the bases of nucleotides
What is a codon?
Base triplet, 3 bases which code for an amino acid
What is a gene?
A section of DNA with a complete sequence of codons for an entire protein.
What is degenerate code?
Amino acids can be coded for by more than one codon.
What is non-overlapping?
Codons are read from base 1-3, and then 4-6 etc, so there is no overlapping of codons.
How many possible combinations of codons are there?
4 base types - 4 x 4 x 4 = 64
How many start and stop codons are there?
1 start codon (methionine) 3 stop codons - don’t code for any amino acid
