DNA and The Genetic Code

DNA

• Chromosomes and their genes are made of a molecule called DNA (deoxyribonucleic acid).
• Each chromosome is made of a very tightly coiled DNA.
• These DNA molecules contain the instructions to control what cells are made of and what they do.

Chromosomes

• Chromosomes in the nucleus carry the genetic information of a cell.
• There are 46 chromosomes in the human body and there are 23 matching pairs, which are all produced by Mitosis.
• Human sex cells have a set of 23 unpaired chromosomes.
  • These sex cells are produced by Meiosis.

Cell Division

• There are two types of cell division: mitosis and meiosis.
• Cell division is conducted in order to grow and repair, as old cells die and new cells produce.
• Cell division is not simply cells being split in half, but is rather a complex process of genetic information being replicated and then split.

Mitosis and Meiosis

Mitosis

• Mitosis is also called “copying division”. It is when a cell replicates itself, then divides itself in order to create new cells without losing genetic information.
• Each new cell has a full set of chromosomes and is identical to the original cell.

Meiosis

• Meiosis is also called “reduction division”. It is when a cell makes a copy of each chromosome, then divides itself twice.
• This in turn makes four new cells with half the original amount of chromosomes.
• This type of cell division is also used to create sex cells.