What is DNA ?What is DNA ?

The chemical nameThe chemical name

Deoxyribonucleic acidDeoxyribonucleic acid

Why is it important?Why is it important?

DNA can be taken from blood, DNA can be taken from blood, semen, or skinsemen, or skin

Everyone's DNA is differentEveryone's DNA is different DNA from a suspect can be DNA from a suspect can be

compared with DNA from a crime compared with DNA from a crime scenescene

Where?Where?

In In every cellevery cell In the In the nucleusnucleus Make up Make up chromosomeschromosomes Found in Found in genesgenes

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…

What do chromosomes What do chromosomes look like?look like?

Made from?Made from?

Four Four basesbases - A, T, C, G - A, T, C, G Two chains running in opposite Two chains running in opposite

directions twisted into a double directions twisted into a double helixhelix (spiral) (spiral)

The long spiral chains are made of The long spiral chains are made of sugarsugar and and phosphatephosphate

The bases are like rungs on a The bases are like rungs on a ladderladder

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 deoxyribonucleic

acid.

Each chromosome is a very long molecule

of tightly coiled DNA.

What is DNA?What is DNA?

CopyingCopying

DNA can copy itself easilyDNA can copy itself easily The strands first unwindThe strands first unwind Each single strand is used as a Each single strand is used as a

template for a new double strandtemplate for a new double strand The DNA has to be copied before The DNA has to be copied before

cells divide ( this happens when cells divide ( this happens when you grow)you grow)

The structure of DNAThe structure of DNA

The double helix ‘ladder’ of a DNA molecule is held together by ‘rungs’ made from pairs of chemicals called bases.

DNA and base pairsDNA and base pairs

There are four types of bases, and they are usually identified by their initials.

A

T

C

G

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!

How do bases pair How do bases pair together?together?

A T C G

Questions Questions 1.1. Why is it important for forensic Why is it important for forensic

scientists to know about DNA?scientists to know about DNA?

2.2. What is DNA and where is it found?What is DNA and where is it found?

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

4.4. What is the difference between What is the difference between chromosomes, genes and DNA?chromosomes, genes and DNA?

Presentation Presentation

Make a presentation explaining :Make a presentation explaining :

why DNA is usefulwhy DNA is useful where it is foundwhere it is found what it is made fromwhat it is made from

Make sure your presentation has Make sure your presentation has illustrationsillustrations

Use the links on the next slide to helpUse the links on the next slide to help

Useful linksUseful links

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

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

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

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

homeworkhomework

Time your skill at the dustbin Time your skill at the dustbin game!game!

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