The life of a eukaryotic cell is represented in a cycle
The Mitotic phase (MITOSIS) means the division of the nucleus of the cell. In order for the nucleus of the cell to divide, it first has to make sure it has the DNA needed for each of the new cells it’s dividing into. How does that happen? In a process called DNA Replication
First let’s review DNA? DNA stands for DeoxyriboNucleic Acid. DNA carries the blueprint or genetic code for building a whole organism DNA is found in the nucleus of eukaryotic cells and within the cytoplasm of prokaryotic cells. DNA is made of longs chains of nucleotides.
A DNA nucleotide consists of 3 parts: Phosphate Deoxyribose sugar Nitrogenous base
The nitrogen bases of the two long chains of nucleotides are held together by a weak hydrogen bond DNA The DNA molecule is twisted and often referred to as a double helix The nitrogen bases that bond together are Adenine with Thymine (A-T), Guanine with Cytosine (C-G)
Back to the Cell Cycle In order for the cell to divide, it first has to replicate it’s DNA (synthesis phase). What does the word replicate mean?
Let’s simulate the process of DNA Replication Obtain a paper DNA strand from your instructor. You will need a pencil.
Fold both sides along dotted lines under the paper (see image steps below).
Bring the folded edges up toward the middle of the paper and flatten each side (see image steps below).
Write down the complementary nitrogenous base along the 3’ side using Chargaff’s base pairing rule (A-T, C-G). This will be your simulated original DNA molecule Highlight both sides of your original DNA molecule (Use only one highlighter color).
Now you are going to start the DNA Replication process Act as the helicase enzyme which is responsible for unwinding and opening the DNA molecule (which means the hydrogen bonds have to be broken). The students need to simulate this process by opening up their original DNA strand. This opening creates a replication fork
Now you need to act as the DNA polymerase enzyme which is responsible for correctly matching up the complementary nitrogenous bases. Simulate this process by writing in the complementary nitrogen bases to each original DNA strand
Compare the two newly replicated DNA strands to the original DNA strands. Tell a neighbor what you notice about the newly replicated DNA strands.