2. DNA Replication & Mitosis

Success Criteria

Your learning has been successful if you can do the following:

I can use the complementary base-pairing rule to help explain the process of DNA replication.
I can describe the processes and products of mitosis.

Vocabulary

Learn these so you can communicate this concept well.

Daughter cell: Cells produced by the process of meiosis. These cells are diploid and are identical to the parent cell.
Diploid: 2n (having two sets of each chromosome)
DNA replication: The process of DNA making a copy of itself during cell division.
Enzyme: A type of protein that either breaks apart or builds up molecules in a chemical reaction. It has an active site with a very specific shape.
Mitosis: The type of cell division for growth and repair.
Replicated chromosome: A chromosome that has undergone DNA replication, and is made up of two sister chromatids.
Semi-conservative: Where the daughter DNA molecule is made one original strand and one new strand.
Sister chromatids: Two identical copies of the same chromosome, formed by DNA replication.

Hei Mahi (Do Now)

Answer these in your OneNote/Notebook - Do not write the questions:

1. What are homologous chromosomes?

2. Why is DNA called a double helix?

3. What does 'complementary base pairing' mean?

Exit Task

In your Learning Journal:

Re-write this interpreting question so it is asking about DNA Replication and Mitosis:

What is the order?

Then, write an answer for it.

Replicated Chromosomes

Most cells have to make copies of themselves as they get old and worn out or when an organism grows in size. This type of cell division for growth and repair is called MITOSIS.

Before mitosis happens, each chromosome needs to make an exact copy of itself. This is so that each DAUGHTER CELL produced during mitosis has a full set of DNA. A chromosome that has undergone DNA REPLICATION is called a REPLICATED CHROMOSOME. Each of the “sides” of the replicated chromosome is called a SISTER CHROMATID.

You must understand the difference between DNA, chromosome, homologous pairs of chromosomes, chromatid and sister chromatids. If you are confused, watch the video below.

A cell containing two copies of each chromosome is referred to as a 'diploid cell'.

DNA Replication

S1.9 (2) DNA Replication & Mitosis

DNA REPLICATION needs:

A supply of free nucleotides
Energy from respiration (“burning” glucose inside your cells)
Enzymes to make the process happen (Helicase, Polymerase and Ligase)
Information or a “blueprint” in the existing DNA

Step 1: An ENZYME (helicase) unzips the DNA (breaks the bonds between the bases) to expose the bases.

Step 2: A different enzyme (DNA polymerase) pairs up and joins free, complementary bases to the exposed bases on the unzipped DNA strand.

Step 3: The daughter DNA (which is one-half old DNA and one-half new DNA – called SEMI-CONSERVATIVE REPLICATION) is completed by another enzyme (ligase) which completes the phosphate sugar backbone.

Mitosis

MITOSIS is the way that cells make new cells, so that old, worn out cells can be replaced and new cells can be made so you can change, grow and get bigger.

Mitosis is cell division, meaning that body (somatic) cells divide to make new body cells.

It is important to remember that during mitosis:

The homologous chromosomes line up single file at the equator.
There is one division.
The two daughter cells produced are identical to the parent cell.
The two daughter cells produced are DIPLOID, meaning they are 2n (in humans, 2n = 46 chromosomes).