DNA

 

What is DNA?

 

DNA is a double helix polymer in the nucleus that makes up our genetic code. 

A gene is a section of DNA that codes for one protein . 

A genome is all the DNA of an organism.

 

Genomes can be used medically for many reasons:

1. Find disease genes  

2. Treat inherited disorders  

3. Track human migration

 

You need to be aware of DNA structure (Biology Only)

 

Nucleotide = sugar + phosphate + base  

Bases: A, T, C, G  

 

If you do HT, you need to be aware that A will only bind to T and C to G.  A ↔ T, C ↔ G *(HT Only)*

 

DNA is read in triplets. This means that every 3 bases are read and this corresponds to 1 amino acid. Once many triplets are read off to get many amino acids, the amino acids can then be joined to form a protein.

 

(Diagram)

 

Protein Synthesis (HT Only)

 

Higher tier students need to understand the steps of protein synthesis:

 

1. Gene uncoiled → template made  

2. Template → ribosome  

3. tRNA brings amino acids  

4. Amino acids join → protein chain  

5. Folds into 3D shape → function

 

These proteins made in protein synthesis fall into 3 main categories:

1. Enzymes e.g. protease

2. Hormones e.g. insulin

3. Structural e.g. collagen

 

Mutations can occur in the base sequence of DNA due to UV exposure, carcinogens or natural causes.

 

These usually have no effect but they can potentially change the amino acid order. This can change the way the protein folds and make it the wrong shape. This may mean that the enzyme no longer fits the substrate a

  ◦ Enzyme no longer fits substrate  

  ◦ Collagen weak

 

Non-coding DNA → switches genes on/off