I explain the stages of the cell cycle and the structure of DNA as well as evaluating the cell cycle and DNA sequence.
I then discuss different things that can go wrong during each stage of replication and finally I evaluate the impact of variation in the DNA sequence using strengths and weakne...
DNA replication is the copying of the DNA that is inside the billions of cells in the human body.
This starts off as the cell cycle.
Interphase
The first stage of this is called Interphase which has three mini stages. The first stage of
interphase is known as gap 1 (G1) which is the first growth stage in which the cell grows in
size and then it synthesises mRNA and the proteins that are required for DNA synthesis. The
second stage of interphase is the (S) synthesis stage and it’s the part in which the DNA is
replicated which occurs between the first and second gap of interphase and in the synthesis
stage, the enzyme helicase unwinds the double helix of the DNA and then the enzyme DNA
polymerase rebinds to the strands. The last stage of interphase (G2) is the second growing
phase and during DNA synthesis and mitosis. The cell will continue to grow in size and produce
more new proteins which ensures that the cell will have enough vital elements to split into two
cells. The next stage of the cell cycle is prophase and this stage has a direct stage in
chromosomal behaviour as the chromosomes condense; microtubules then form in the cell
cytoplasm from the proteins present and the
Cellular checkpoints
Checkpoints are thought of as safety gaps during which a cell check that the DNA as well as
the intercellular components have properly duplicated. If this isn’t the case, suppressor genes
can intervene with the process of apoptosis.
Prophase
This is the first stage of the cell cycle after interphase and there is a direct change in
chromosomal behaviour as the chromosomes condense. The microtubules then form in the
cytoplasm from the proteins present and the nuclear envelope breaks down, removing the
barrier for genetic information.
Metaphase
This is the second stage of the cell cycle and the now condensed chromosomes are now pulled
to the centre of the cell. This means that the physical nature of the chromosomes is altered
but so is the environment. The chromosomes then line up along the ‘metaphase plate’
meaning the genetic information has changed shape and the location but still follows an
organised system.
Anaphase
This is the third and penultimate stage of the cell cycle. The chromosomes go under another
change in behaviour by dividing at the centromere which is where the four arms of the
chromosomes meet. The chromosomes are split by a structure known as the mitotic spindle
There is now floating chromatids that are long and short that are pulled by the spindle to
opposite sides of the cell. Precise alignment is important in the cell cycle as it ensures equal
genetic division.
Telophase
Telophase is the last stage of the cell cycle. This stage separates the genetic material from the
two parent cells into two identical daughter cells. It begins by forming a new nuclear envelope
around the new chromosomes so it can reinstate the environmental barrier needed around the
chromosomes. The chromosomes now are able to uncoil and return to their original form after
this, Cytokinesis takes place which it is the actual process in which the cells divide as well as
where the cytoplasm also divides.
The structure of DNA
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