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Biology B2. Lesson 3: DNA. Connect. On each post-it, write one fact that you think you already know about DNA . Stick this on your desk. Collect an exam question. Connect. DO NOT ANSWER the exam question. Instead, write your own ‘Walking Talking’ Notes onto it. What Are We Learning?.

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Biology B2

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Biology B2

Lesson 3: DNA


Connect

  • On each post-it, write one fact that you think you already know about DNA.

  • Stick this on your desk.

  • Collect an exam question.


Connect

  • DO 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.


Today’s Learning

Progress Step 1:

Be able to describe the simple structure of DNA and use some key words.

Progress Step 2:

State the key parts of a DNA molecule.

Progress Step 3:

Describe the structure and function of DNA

Increasing Difficulty


Starting Points

  • DNA stands for DeoxyriboseNucleic 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


DNA: The Basic Structure

Sugar

Hydrogen Bonds

Phosphate


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.


Rosalind Franklin

Franklin’s “Photograph 51”

Watson & Crick’s ball and stick model


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.


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