DNA DeoxyriboNucleic Acid LEARNING OBJECTIVES: Describe structure of DNA molecule Explain that DNA codes for specific protein

Where is DNA? How is DNA packed in the nucleus? 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 rung strands 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. rung strands

Can you match the base pairs?

DNA contains 4 different bases: __________ (G) The bases are always paired in the same way: Adenine pairs with ………………………….. Cytosine pairs with …………………………..

Boardworks GCSE Science: Biology Genes and Genetic Engineering What are proteins? Boardworks GCSE Science: Biology Genes and Genetic Engineering Proteins are made of long chains of amino acids. There are 20 different types of amino acid from which to make proteins. protein molecule 1 amino acids What happens if the amino acids are in a different order? protein molecule 2 Different combinations of amino acids make different proteins.

Why are proteins so important? Our bodies use proteins all the time They are an important component in every cell Proteins are needed for almost all functions of the cell Proteins are used for : Making: Building & repairing tissues Making enzymes ……………..and millions of other functions in our bodies.

How does DNA control the cell? G A sequence of three bases is called a ……………………… or a ……………………… C A 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 a certain lengths of the DNA molecule code for different proteins. Some amino acids have more than one code e.g. arginine = GCA & AGT. A T A G

Boardworks GCSE Science: Biology Genes and Genetic Engineering 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. amino acid base sequence

What is the order of amino acids in this protein code? 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 are vital for our cells to function. What is the order of amino acids in this protein code? G C A T A C G C A T A C A T A 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. triplet bases helix genetic guanine thymine coding