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Human Biology: DNA Replication - Coggle Diagram
Human Biology: DNA Replication
What is it
DNA replication is the process by which a cell makes an identical copy of its DNA. This process is performed at the beginning of every cell division so that when the cell divides, each daughter cell will inherit an identical copy of the DNA.
Why does it occur
DNA replication is important because we need cells to survive and after our current cells die we need to replace them with new cells
When does it occur
It occurs during interphase which happens before mitosis and miosis
Step One
Unwinding the DNA molecule
A normal chromosome consists of a single DNA molecule packed into a single chromatid
The long molecule of double stranded DNA must be untwisted at high speed at its replication fork by two enzymes
Helicase: unwinds the parental strands
DNA gyrase: relieves the strain that this generates by cutting, winding and re-joining the DNA strands
PCR
Polymerase chain reaction, or PCR, is a technique to make many copies of a specific DNA region in vitro (in a test tube rather than an organism)
PCR has many research and practical applications. It is routinely used in DNA cloning, medical diagnostics, and forensic analysis of DNA.
https://www.khanacademy.org/science/biology/biotech-dna-technology/dna-sequencing-pcr-electrophoresis/a/polymerase-chain-reaction-pcr
Step Two
Making new DNA strands
The formation of new DNA is carried out mostly by an enzyme complex called DNA polymerase, and a series of protein that cause the two strands to break apart
On one side (the leading strand), nucleotides side (the lagging strand) fragments of a single-stranded DNA between 1000-2000 nucleotides long are created (Okazaki fragments)
These will be later joined together to form one continuous length
Step Three
Rewinding the DNA molecule
Each of the two new double-helix DNA molecules has one strand of the original DNA (dark grey and white) and one strand that is newly synthesised (patterned)
The two DNA molecules rewind into their 'cork-screw' double-helix shape again
Each double-helix is then coiled around histone proteins and further wrapped up to form separate chromatids (still joined by a common centromere)
The new chromosome has actually has twice as much DNA as a regular )non-replicated) chromosome
The two chromatid will become separated in the cell division process to form two separate chromosome