15 OrGanIC CHemIsTry 2
a Testing for a protein.
b Adding dilute sodium hydroxide.
Figure 15.26 Crick and Watson based this model for DNA on X-ray studies performed by Rosalind Franklin and chemical analysis.
Genes are the units of heredity that control the characteristics of organisms. A gene is made of DNA. No two individuals have the same DNA sequence. DNA ‘fingerprinting’ has become a very powerful forensic science tool in the investigation of crime (Figure 15.27).
c Adding 1% copper(ii) sulfate.
d The purple colour shows the presence of a protein.
Figure 15.25 The Biuret test.
DNA Deoxyribonucleic acid (DNA) belongs to a group of chemicals called the nucleic acids (Figure 15.26). They are also biopolymers. DNA controls the prot ein synthesis within your cells. When you eat a food containing proteins, such as meat or cheese, your digestive enzymes break down the proteins present into individual amino acids. The DNA in your cells controls the order in which the amino acids are repolymerised to make the proteins you need!
Figure 15.27 Identical patterns shown by DNA fingerprinting can identify the criminal.
Questions 1 Which two functional groups do amino acids possess? 2 How many amino acids have to be involved before the biopolymer is called a protein? 3 Name the process by which the individual amino acids in a protein are released by reaction with a dilute acid. 4 Explain how DNA fingerprinting may be used in paternity suits.
245