DNA

What do you know about it?

The Secret of Life…Watch the following video and answer the questions about the discovery of DNA!

DNA Extraction

• Having looked at the card sort try to put the steps in order.

• Why is each step important?

DNA Extraction1 – Collect berries as allocated and a pestle and mortar. 2 - Mash the berries using the pestle and mortar. This is to break open some of the cells.3 – To make an extraction buffer, add 10ml water, 1ml detergent and 1 spatula of salt to a small beaker and stir slowly until the salt dissolves. 4 - Add the extraction buffer to the mashed up berries and mix well using the pestle and mortar.

DNA Extraction5 – Transfer the mixture to a test tube and incubate at 60oC for 15 minutes. This starts to break down the cell’s membranes.6 - Filter the berry mixture through a funnel & filter paper into a clean test tube until it is about 1/3 full. This separates the parts of the cell leaving a liquid containing the berry DNA. 7 – Using a dropper pour the ice cold ethanol slowly down the side of the test tube. The ethanol makes the DNA visible as it is insoluble in ethanol.8- Use a paperclip to hook the white jelly-like substance forming. This is the DNA!

DNA

Genetic information is stored in the nucleus of a cell.

• Genetic information is especially found on thread-like structures called, chromosomes.

• Genes are located on chromosomes in the nucleus.

• Genes and chromosomes are made of DNA.

• DNA stands for Deoxyribonucleic Acid.

• DNA has a double helix shape and is made of 4 bases.

• The 4 bases are shown as; A, C, T and G

Organisms to Bases...• Cut out the names and definitions in

the cardsort. • Arrange the names in order of size –

The largest at the top down to the smallest.

• Then match the definitions to the names.

Genes

• Genes are sections of DNA containing the instructions needed to make proteins which are made of amino acids.

Decoding…• Collect a DNA sequence – this will

have a string of letters A, T, G and C to represent the 4 DNA bases.

• Re-write the DNA sequence leaving a space after every third letter e.g. TACACGACCGTCTAG becomes TAC ACG ACC GTC TAG

• Collect a decoder key• Use the decoder to find out which amino acid

(represented by a different shape for each amino acid) comes first in the sequence e.g. in the sequence above TAC is the first code which in the key means ‘START’

• Find the next amino acid in your sequence using the key e.g. ACG is

• Continue adding the correct amino acids to the chain until the chain is complete.

Decoding…

Decoding Posters• Make a poster showing your; • Starting code - TACACGACCGTCTAG• Triplets - TAC ACG ACC GTC TAG• Amino acids - • Protein –

• Are any 2 proteins the same? Why?

Why do we need proteins?• Enzymes are proteins that help us

digest food.• Hair is protein.• Skin contains protein.• Antibodies which fight disease are

proteins.• Our blood contains proteins.

Questions• Where are genes located?• Where are chromosomes found?• What do genes contain the

instructions for making?• Give 3 examples of proteins found in

your body.

Inheritance• Each person’s DNA is unique.• This is because they inherit their

genes from their parents.

Inheritance• Sometimes a change if the order of

the code occurs in the genes which are passed on from parents to offspring.

• This leads to faulty proteins and inherited diseases.

• Examples include; Cystic Fibrosis and Huntingdon’s Disease.

Questions• Why can DNA be used to identify the

father or a child?• Why can DNA be used to identify

criminals?• Explain how inherited diseases arise?

Inherited Diseases TaskCollect an inherited disorder Case Study card.

You have been given a scenario related to a specific disease caused by a problem with the genetic code for a particular gene.

Starter sites for research:http://learn.genetics.utah.edu/content/disorders/whataregd/ (Huntington’s and cystic fibrosis)

http://genome.wellcome.ac.uk/doc_wtd020857.html or http://www.genome.gov/10001214 (haemochromotosis)

http://www.genome.gov/10001220 (Tay Sachs)

DNA StructureDNA is double stranded.

DNA is a double helix shape.

The “rungs” of the ladder of DNA are made of 4 bases, A, C, T, G.

DNA StructureDNA carries the instructions to make proteins.

The order of bases determines the order of amino acids.

The amino acid sequence determines the type of protein which is made.

DNA Bracelet• From the sequence you have been

given make a bracelet to show the order of bases which codes for……

DNA Bracelet• Use your instructions sheet to make

your bracelet.• Be careful to use the right colour for

each base!

• Remember A matches T, C matches G!

Edible DNA!!• Follow the recipe to make your edible

DNA!

Edible DNA!!• Using your bracelet and edible DNA

explain to your partner the structure of DNA.

• Tell your partner why the order of the bases is important?

• What does your sequence code for?

Quick Check• What instructions does DNA carry?

• Where is DNA found in the cell?

• Where are proteins made in the cell?

DNA to Protein• Watch the following video as an

introduction to DNA being used to make protein.

DNA to Protein• So that the instructions for making

protein can pass from the nucleus to the ribosome a new molecule must be made……..

• Messenger RNA (mRNA)

DNA to Protein• Messenger RNA (mRNA) takes a copy

of the code from DNA in the nucleus to the ribosome.

• At the ribosome amino acids are assembled into a protein as directed by the code.