Biggest Ever Maths and Science Lesson Investigating DNA Attempt to break the GUINNESS WORLD RECORD 3 November 2015 This is a very special lesson because thousands of classes around the world are sharing this same lesson today. Image thanks to Dr John Molot, Environmental Medicine

DNA is what makes you a very special human being, different from every other living thing. You have identical copies of the same DNA in every cell in your body and your DNA is different from any other DNA.

DNA carries the message which made you grow from a single cell into the person you are now. For the whole of your life DNA controls how your body works and grows and changes.

In this lesson we find out what DNA is, how it carries the messages that control all living things and how it copies itself. sci_tech/2000/human_genome/default.stm

THE SHAPE OF DNA DNA is like a twisted ladder. Each step of the ladder is made up of two bases. There are only four types of base A, T, C and G: base A always pairs with T, and C always pairs with G. The chemical names for these bases are adenine (A), thymine (T), cytosine (C) and guanine (G). This shape is called a double helix.

The DNA genetic code is a sequence of the letters A,T, C and G in different orders, with many repetitions, for example: and on and on and on … Our entire DNA sequence is called a genome.

The human genome in your DNA gives the biological instructions needed to make you. The human genome has about 3 thousand million base pairs. Image from Scientific American

If all the DNA in your body were connected it would stretch over 1200 million kilometres (744 million miles)! That’s 1500 return trips to the moon, or 4 return trips to the sun. And all this DNA fits inside you!

The nucleus in each cell in the human body contains 2 metres (6 feet) of DNA. The cell is very small, and as there is so much DNA, it must be tightly packed into packages that are called chromosomes. DNA and CHROMOSOMES

A distinct sequence of the letters that determines one characteristic is called a gene. Humans have about 20,000 genes on 46 chromosomes, 23 inherited from each parent. Our DNA determines all our characteristics, for example our sex, the colour of our skin, hair and eyes, our height, if we have freckles or not, if we can roll our tongues, if we are likely to get certain diseases … etc.

In 1953 Francis Crick and James Watson discovered the double helix structure of DNA. Rosalind Franklin’s X-ray studies of DNA gave them the clue to this structure. Rosalind Franklin died in She was not awarded the Nobel Prize that went to the other three scientists in 1962.

A rough draft of the human genome (the complete DNA sequence) was completed in the year The final map of the human genome was completed by many scientists and mathematicians in There are an estimated 20,000 to 25,000 genes in our genome and there is still a lot more to find out about them. The study of the human genome is crucially important to modern medicine, in understanding disease, and in trying to find new treatments.

Gene switches are what really make humans tick Our bodies have many different types of cells that differ because some genes are switched on and some are switched off in each cell. Some genes are only switched on during the development of a baby. After birth their job has been completed and they are switched off.

All living things have DNA. Parts of the DNA of any two different species may be the same but other parts will be different. Here are some examples of small parts of the DNA of different species.

DNA is made of chemical building blocks called nucleotides. To form a strand of DNA, nucleotides are linked into chains.

Pairs of nucleotides link together to form DNA. As cells divide, DNA divides to form 2 exact copies of itself so that each new cell has a copy of the DNA.

The nucleotides in the DNA separate, and new nucleotides that are floating in the nucleus of the cell join onto the two parts to make two exact copies of the DNA. As the DNA splits lengthwise the nucleus itself splits into two, replacing the original cell by two new cells that are exact copies of the original cell. CELL REPRODUCTION

There are many ways to make DNA models. Now it is your turn to make your own. Have fun! Download free resources from Paper Origami Pipecleaners Sweets and Toothpicks