Unit 1: DNA and the Genome

DNA and the Genome

Unit 1: CFE Higher BiologyJune – October

Unit Assessment – before October break

CFE Higher BiologyDNA and

the Genome

Key area 1: The structure of DNA

CFE Higher BiologyDNA and

the Genome

Take a moment…think…

What have you learned about DNA so far?In groups, collect an sheet of poster paper.

Nominate a scribe. Write down as many things you can remember about DNA from your school/life so far.

DNA

CFE Higher BiologyDNA and

the Genome

Carousel

Pass the sheets around.

Read the facts/comments. Put a tick next to any you had on your sheet.

Add any you had that are missing.

CFE Higher BiologyDNA and

the Genome

Share with class

Share what is on your sheet with the class.

The aim is to fill a sheet of your jotter with “DNA background information”.

CFE Higher BiologyDNA and

the Genome

Key concepts• DNA is inherited.• DNA is the genetic material of living things.• DNA is located within the nucleus of all cells apart from red

blood cells.• DNA is a long chemical sequence and this sequence contains

the information needed for that living thing to develop, survive and pass its genetic information on to the next generation.

• The DNA chemical sequence differs between individuals. The pattern of this sequence is called the genotype.

Unit 1: DNA and the Genome

The structure of DNA

CFE Higher BiologyDNA and

the Genome

Prior knowledge

• DNA is the genetic material.

CFE Higher BiologyDNA and

the Genome

Deoxyribonucleic acid

The DNA molecule is comprised of two chains of nucleotides.

The nucleotides are comprised of a sugar, a phosphate and a base.

CFE Higher BiologyDNA and

the Genome

Nucleotides

Phosphate

Sugar

Base5’ end

3’ end5’

pronounced “5 prime”

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the Genome

Why 5’ and 3’?This is what a nucleotide looks like at the molecular level…

…lets zoom in to look at the sugar in more detail…

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the Genome

Carbon 1

Carbon 2Carbon 3

Carbon 4

Carbon 5

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the Genome

Nucleotides in a chain are joined together by sugar-phosphate bond to make long chains of nucleotides – called polynucleotides.

(poly = many)

CFE Higher BiologyDNA and

the Genome

The bases

In DNA there are four different bases:AdenineThymineCytosineGuanine

or A, T, C and G

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the Genome

Base pairing

These bases are described as being complementary to each other. This means their shapes match up.

CFE Higher BiologyDNA and

the Genome

DNA base pair rules

Adenine always joins to Thymine

Cytosine always joins with Guanine

The bases are joined by hydrogen bonds.

CFE Higher BiologyDNA and

the Genome

The double helix

The chains of polynucleotides are joined together by the bases, by hydrogen bonds, for form a double helix structure.

CFE Higher BiologyDNA and

the Genome

Imagine the sugars and phosphates joined together making the side of a ladder, with the pairs of bases forming the rungs.

Then the ladder gets twisted…

CFE Higher BiologyDNA and

the Genome

CFE Higher BiologyDNA and

the Genome

The double helix is described as having two anti-parallel chains of nucleotides because one side goes from 5’ to 3’ and the opposite side goes from 3’ to 5’.

CFE Higher BiologyDNA and

the Genome

How was all this discovered?Who would have thought that science could produce such a story of intrigue and characters? Like all major scientific discoveries, the discovery of the structure of DNA by James Watson and Francis Crick in 1953 was the result of years of work from a great number of scientists. Not only is the story one of great scientific interest, it is also one of great human interest and controversy.

CFE Higher BiologyDNA and

the Genome

Your taskThis task will see you research one of the individuals or groups of scientists whose work contributed to the discovery. There are six people to choose from and your teacher will help you decide which one to focus on:•Griffiths•Avery et al.•Hershey and Chase•Chargaff•Franklin and Wilkins•Watson and Crick 

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the Genome

The results of your research will then be produced as a scientific poster, which you will present to the class.• who the scientist(s) is, where they worked

and when• the aims of the experiments• what the experiments were, including a

diagram• what the conclusions were• other interesting information that you have

gathered that lends interest to the story.

CFE Higher BiologyDNA and

the Genome

Read the instruction sheet for more details.

CFE Higher BiologyDNA and

the Genome

Key concepts• DNA is composed of two polynucleotide chains.• Nucleotides consist of a sugar, phosphate and base.• Nucleotides bond to form a sugar–phosphate

backbone.• The two polynucleotide chains run antiparallel, with a

deoxyribose sugar at the 3′ end and a phosphate group at the 5′ end.

• The nucleic acid bases are paired by hydrogen bonding in the centre to form a double helix.

• Base pairing is specific, with adenine pairing with thymine and cytosine pairing with guanine.