DNA and the genome 6.1.3

• chromosomes are thread like structures made of DNA and contain thousands of genes
• DNA is genetic material
• genes code for different proteins which form our characteristics, different forms of the same gene are called alleles. genes are a unit of inheritance and normal body cells have 2 copies of the same gene
• there are 3,300 million base pairs
• you have approximately 20,000 - 25,000 genes
• DNA is a polymer which is a long molecule made up of repeating units
• repeating units of DNA are called nucleotides
• Dna is a polynucleotide
• DNA polymer is made up of 2 strands twisted to form a double helix structure the two strands that run in opposite directions are held together by weak intermolecular forces
• A always pairs with T
• C always pairs with G
• the bases are complementary with weak intermolecular bonds
• genes are small sections of DNA each of which determines an inherited characteristic
• a gene is used to code for a template called mRNA that moves to the ribosome
• the mRNA is used to determine the particular sequence of amino acids to make a specific protein
• specialised cells will express certain genes so they make proteins they need eg only red blood cells will make haemoglobin, even though every cell has the gene for haemoglobin
• so genes control the proteins, which control the make-up of the different specialised cells that from tissues which then form organs, and organ systems, to make up the organism
• amino acids are produced from the mRNA message as a protein equivalent
• a genome is the entire genetic material of an organism
• the human genome project was designed to sequence the entire human genome (genetic material)
• the project was unusual because:

  • it was 2 years ahead of schedule
  • it was under budget
  • it had teams of scientists worldwide
• scientists continue to sequence more human genomes because they want to understand genetic diseases more to be able to help treat them in the future, they can also be used to identify differences and similarities between people for ancestry apps or websites
• closely related groups have fewer genetic differences, ie ethnicity