MYP Biology 4 Activity
DNA - Deoxyribonucleic Acid
LEARNING OBJECTIVES:
•
Describe structure of DNA molecule
•
Explain that DNA codes for specific protein
Where is DNA?
Although a human cell is only a few hundredths of a millimetre in diameter, each one
contains more than a metre of DNA.
How is DNA packed in the nucleus?
DNA is twisted into a spiral called a ……………………………., which is tightly coiled up to form
…………… . Genes are packed along the length of chromosomes, which are stored in the
………………….
The Structure of DNA
The DNA molecule is like a twisted …………....….. (double helix).
Two strands are made up of ……………….... & …………………..
The rungs are made up of ……………………………….., which link the strands together.
MYP Biology 4 Activity
Can you match the base pairs?
DNA contains 4 different bases:
__________ (A)
__________ (G)
__________ (T)
The bases are always paired in the same way:

Adenine pairs with …………………………..

Cytosine pairs with …………………………..
What are proteins?
__________ (C)
MYP Biology 4 Activity
Why are proteins so important?
•
Our bodies use proteins all the time
•
They are an important component of every cell
•
Proteins are needed for almost all functions of the cell
Proteins are used for :
1. ………………………………………………………………………………………………………...
2. …………………………………………………………………………………………………………
3. …………………………………………………………………………………………………………
How does DNA control the cell?
Each ‘codon’ codes for a certain amino acid, for example:

GCA codes for ‘arginine’

ATA codes for ‘tyrosine’

TAC codes for ‘methionine’

CAA codes for ‘proline’
Therefore, certain lengths of the DNA molecule code for different proteins.
Some amino acids have more than one code e.g. arginine = GCA & AGT.
DNA controls the joining together of amino acids to make a specific protein in a cell. The
order of bases in a section of DNA decides the order of amino acids in the protein.
MYP Biology 4 Activity
The order of the base pairs is critical in DNA, as it is this that determines the order of the
amino acids in a protein, which is vital for our cells to function.
1. What is the order of amino acids in this protein code?
GCATACGCATACATA
2. What is the sequence of bases in this amino acid chain?
methionine-tyrosine-arginine-proline-tyrosine
Summary of the Lesson
A molecule of DNA is shaped like a twisted ladder, called a double __________. The ‘rungs’
of the ladder are made up of pairs of __________. Adenine pairs with __________, and
cytosine pairs with __________. DNA carries the __________ code, which tells the cell to
make proteins. The DNA strand that can do this is called the _________ strand. A group of
three bases is called a __________. Each of these is the code for one amino acid in the
protein.