What is DNA ?

The chemical name Deoxyribonucleic acid

Deoxyribonucleic acid

Why is it important? DNA can be taken from blood, semen, or skin Everyone's DNA is different DNA from a suspect can be compared with DNA from a crime scene

DNA can be taken from blood, semen, or skin

Everyone's DNA is different

DNA from a suspect can be compared with DNA from a crime scene

Where? In every cell In the nucleus Make up chromosomes Found in genes

In every cell

In the nucleus

Make up chromosomes

Found in genes

What do chromosomes look like? Chromosomes are long strands of genetic information located in the nuclei of cells. Chromosomes are most visible during cell division when they replicate and look like this…

Made from? Four bases - A, T, C, G Two chains running in opposite directions twisted into a double helix (spiral) The long spiral chains are made of sugar and phosphate The bases are like rungs on a ladder

Four bases - A, T, C, G

Two chains running in opposite directions twisted into a double helix (spiral)

The long spiral chains are made of sugar and phosphate

The bases are like rungs on a ladder

What is DNA? Chromosomes and their genes are made of a molecule called DNA . DNA molecules carry the code that controls what cells are made of and what they do. DNA stands for d eoxyribo n ucleic a cid. Each chromosome is a very long molecule of tightly coiled DNA.

Copying DNA can copy itself easily The strands first unwind Each single strand is used as a template for a new double strand The DNA has to be copied before cells divide ( this happens when you grow)

DNA can copy itself easily

The strands first unwind

Each single strand is used as a template for a new double strand

The DNA has to be copied before cells divide ( this happens when you grow)

The structure of DNA

DNA and base pairs The double helix ‘ladder’ of a DNA molecule is held together by ‘rungs’ made from pairs of chemicals called bases . There are four types of bases, and they are usually identified by their initials. A T C G

How do bases pair together? Base pairs hold the two strands of the DNA helix together. The rules for base pairing are… There are millions of base pairs in a DNA molecule, and they always follow these rules. ‘ A’ always pairs with ‘ T’ ‘ C’ always pairs with ‘ G’ It is the sequence of these bases along a DNA molecule that forms the genetic code – it’s that simple! A T C G

Questions Why is it important for forensic scientists to know about DNA? What is DNA and where is it found? Describe the structure of DNA and explain how this makes it possible to reproduce (replicate) itself easily What is the difference between chromosomes, genes and DNA?

Why is it important for forensic scientists to know about DNA?

What is DNA and where is it found?

Describe the structure of DNA and explain how this makes it possible to reproduce (replicate) itself easily

What is the difference between chromosomes, genes and DNA?

Presentation Make a presentation explaining : why DNA is useful where it is found what it is made from Make sure your presentation has illustrations Use the links on the next slide to help

Make a presentation explaining :

why DNA is useful

where it is found

what it is made from

Make sure your presentation has illustrations

Use the links on the next slide to help

Useful links http://www.sciencemuseum.org.uk/exhibitions/genes/99.asp http://www.factmonster.com/ce6/sci/A0836145.html http://www.bbc.co.uk/schools/gcsebitesize/biology/variationandinheritance/0dnaandgenesrev2.shtml http://www.topmarks.co.uk/

http://www.sciencemuseum.org.uk/exhibitions/genes/99.asp

http://www.factmonster.com/ce6/sci/A0836145.html

http://www.bbc.co.uk/schools/gcsebitesize/biology/variationandinheritance/0dnaandgenesrev2.shtml

http://www.topmarks.co.uk/

homework Time your skill at the dustbin game! http://griggans.edublogs.org/2008/04/30/dna-dustbin-game/

Time your skill at the dustbin game!

http://griggans.edublogs.org/2008/04/30/dna-dustbin-game/