• The?entire set of the genetic material?of an organism is known as its?genome
• In 2003, scientists completed a 13-year project in which they sequenced the genes that make up the whole human genome
  • This project was named the?human genome project
  • It helped to develop?medical understanding and treatment?of genetic diseases as well as facilitating the study of?human migration patterns

   

• Each?gene?within the genome is made up of a?small section of DNA?that codes for a?particular sequence of amino acids
• These sequences of amino acids form?different types of proteins
• Alleles?are different versions of a gene
  • e.g. there are different alleles that code for brown or blue eye colour
  • Having 2 alleles of the same type is called?homozygous
  • Having 2 alleles that are different to one another is called?heterozygous

   

• There are many different types of proteins but some examples of these could be:
  • Structural proteins?such as collagen found in skin cells
  • Enzymes
  • Hormones

   

• Genes control our?characteristics?as they code for proteins that play important roles in what our cells do

• DNA, or?deoxyribonucleic acid,?is the?genetic material found in the nucleus?of a cell
• DNA,?is a?polymer?made up of?two strands?coiled around to make a?double helix
• The strands are formed from a?sugar phosphate backbone?with?bases?joined together by?complementary base pairing
  • Adenine pairs with thymine
  • Guanine pairs with cytosine

   

• ?Cell division?and?protein synthesis?both rely on these base-pairing rules because each half of the DNA double helix acts as a?template?to be copied in order to create a complete new double helix

The structure of DNA and complementary base pairs

• In the nucleus?of a cell, the DNA double helix?supercoils?to form structures called?chromosomes
• They are only visible during cell division
• Ordinary human body cells contain?23 pairs of chromosomes
  • This is a?diploid?number (often shown as?2n)
  • One chromosome from a pair is?inherited from each parent
  • Each chromosome pair is called a?homologous pair

   

• The 23rd pair of chromosomes are the?sex chromosomes
  • In females, the sex chromosomes are the same, a?homozygous genotype?(XX)
  • In males, the sex chromosomes are different, a?heterozygous genotype?(XY)

   

• Gametes contain just?23 individual chromosomes
  • This is?half?the full number of a body cell and is called the?haploid?number (or?n)

   

• Genes?are found in?specific locations?on the chromosomes, these locations were identified in the?human genome project

Genes are short lengths of DNA that code for a protein. They are found on chromosomes.