Biology B2

Biology B2Lesson 3: DNA

ConnectOn each post-it, write one fact

that you think you already know about DNA.

Stick this on your desk.

Collect an exam question.

ConnectDO NOT ANSWER the exam

question.

Instead, write your own ‘Walking Talking’ Notes onto it.

What Are We Learning? By the end of this lesson, you should:

Be able to describe the structure of DNA.

Be able to explain how DNA codes for amino acids.

Consider the importance of the discovery of DNA.

SMSC & RWCM Cultural: Consider the reasons why some

discoveries are more important than others.

Social: Respect the views of others.

Reading: Identify key facts.

Writing: Use key words in the correct context.

Progress Step 1:

Be able to describe the

simple structure of DNA and use

some key words.

Progress Step 3:

Describe the structure and

function of DNA

Progress Step 2:

State the key parts of a DNA

molecule.

Increasing Difficulty

Today’s Learning

Starting Points DNA stands for Deoxyribose Nucleic

Acid.

Think: What is the structure of DNA?

Why is DNA so important?

DNA: The Basics Deoxyribose Nucleic Acid can be

descibed as having a coiled double helix shape.

It is unique because it is able to replicate.

DNA: The Basics Each strand of

DNA is made up of a combination of four bases.

The order in which each of these pairs appears is important.

DNA: The Basics In DNA, there are

four bases. These are:

Adenine Guanine Cytosine Thymine

DNA: The Basics The four bases on

one strand line up against the other strand always in the following pairs:

Adenine - Thymine Guanine - Cytosine

DNA: The Basics The four base pairs

are joined by Hydrogen bonds, which can be easily ‘unzipped’.

What do you know about hydrogen bonds?

DNA: The Basics Each triplet of bases on one strand of

DNA codes for an amino acid.

How many combinations of bases can you come up with in four minutes?

DNA: Task How many amino acids are there in this

section of DNA? Use colours to identify them.

-C-G-C-A-A-T-C-G-T-A-T-A-G-C-G-A-A-C-

What would be the opposite strand of this DNA?

DNA: Task How many amino acids are there in this

section of DNA? Use colours to identify them.

-C-G-C-A-A-T-C-G-T-A-T-A-G-C-G-A-A-C-

What would be the opposite strand of this DNA?

-G-C-G-T-T-A-G-C-A-T-A-T-C-G-C-T-T-G

SugarHydrogen Bonds

Phosphate

DNA: The Basic Structure

Discovering DNA DNA was first modelled in 1953 by

James Watson & Francis Crick.

There is an argument that this was the most important scientific discovery of the the 20th Century.

The Nobel Prize in Physiology or Medicine was awarded in 1962 to Watson, Crick and Maurice Wilkins.

Discovering DNA: Task Use the information in the text to

produce a timeline for the discovery of DNA.

Start with the earliest events.

When you are happy, decide which events were the most significant.

Franklin’s “Photograph 51”

Watson & Crick’s ball and stick model

Rosalind Franklin

Questions Which discovery contributed the most

to the work of Watson & Crick? Why was Erwin Chargoff’s work an

important contribution to the deduction of the structure of DNA?

Why was the structure of DNA seen as such an important scientific development?

Franklin: A Victim Of Sexism? Franklin is best known for her work on the

X-ray diffraction images of DNA which led to the discovery of DNA double helix.

Her data, according to Francis Crick (Nobel Prize Winner), were "the data we actually used” to formulate Crick and Watson's 1953 hypothesis regarding the structure of DNA.

What do you think about this?

What Are We Learning? By the end of this lesson, you should:

Be able to describe the structure of DNA.

Be able to explain how DNA codes for amino acids.

Consider the importance of the discovery of DNA.

Reflection Look at your Post It Note from the

beginning of the lesson.

Review what you wrote and comment upon the accuracy of your original comment.

Share one learning point with a neighbour.