DNA replication
- direction: 5’ to 3’
- the process of creating a copy of a DNA molecule
- the process is %%semi-conservative%%, which means that 1) one strand will be newly synthesised and 2) one strand will be from the original template molecule
- continous on the leading strand, while discontinous on the lagging strand
The process of DNA replication:
1) initiation - unwinding of the DNA by helicase enzyme, strands are kept apart by the SSB protein, primers provide an initiation point for the start of replication
2) elongation - nuclotides are linked together by the DNA polymerases (III for the leading strand and I for the lagging strand), since the process on the lagging strand in discountinous Okazaki fragments are made, which are later connected by the enzyme ligase
3) termination - the process ends when the replication forks meet
^^FUN FACT^^ : DNA polymerases add nucleotides only to the 3’ end of a primer
@@Enzymes taking part in the process of replication:@@
- Helicase - unwinds DNA strands by breaking down the hydrogen bonds between nitrogenous bases
- Gyrase - smooths the process, releases torsional strain created by the unwinding of DNA
- SSB (single stranded binding protein) - makes sure both strands stay separated and don’t get digested by nucleases
- Primase - provides an initiation point for DNA polymerases by generating a short RNA primer on both DNA strands
- Polymerase III - links nucleotides on the leading strand
- Polymerase I - links nucleotides on the lagging strand and creates Okazaki fragments
- Ligase - connects Okazaki fragments
- it stops the DNA replication in preparation samples for base sequencing
- enables analisys of sequences
%%Tandem repeats%% (VNTR - variable number tandem repeats) - are used in DNA profiling
- it is a short nucleotide chain / sequence that shows variations between individuals in terms of the number of times the sequence is repeated