3.4, 3.5, 3.6 The Structure of DNA, The Genome and Extracting DNA
DNA
Genes
Extracting DNA from Fruit
Genome
DNA stands for deoxyribonucleic acid, and this is a polymer that contains instructions for the body
DNA is a polymer (long molecule) made up of two strands which are wound around each other to form a structure called a double helix
DNA, found in the nucleus, is a chemical that contains genetic material
Each nucleotide is made up of one sugar molecule, one phosphate molecule (which form the backbone) and one of the four types of organic bases
Each DNA molecule is made up of two DNA strands which are twisted together. Each base is connected to another base in the other strand
The four types of organic bases are A, C, G, T
A bases only connect to T bases, and C bases only connect to G bases. This is called complementary base pairing
It is made up of many small parts called nucleotides
The order of the different bases forms a genetic code - e.g. A, G, T, T, C, A, A etc
Each gene codes for many amino acids, which are joined together to make a specific protein
There are 20 types of amino acid
A gene is a short section of DNA
The word genome describes all the genetic information (DNA) of a single organism
The human genome has been studied, which has improved our understanding of the genes linked to different types of disease, the treatment of inherited disorders and has helped in tracing human migration patterns from the past
What should we see?
Why should we add pineapple juice?
Method
Why do we add ethanol?
Filter the solution using a few sheets of kitchen paper and a sieve. Pour the filtrate into a test tube
Add 10ml of pineapple juice to the filtrate and allow to rest for a few minutes
Add the solution from Step 1 to the kiwi
Add 2 teaspoons of cold ethanol to the solution and wait 10 minutes
Peel the skins of a kiwi and chop into small pieces. Pulverise the kiwis
A white mass should precipitate at the top of the tube after 10 minutes; this is the DNA from the kiwi
Pineapple juice contains an enzyme called bromelain which breaks down proteins attached to the DNA
This helps us see the DNA more clearly
Ethanol causes the DNA to precipitate out of the solution - making it visible at the top of the container
Gently mix together 50ml cold water, half a teaspoon of salt and 10ml washing up liquid. Gently heat this mixture at 50C for 5-10 minutes
It is possible to extract DNA from fruit using household ingredients