Inheritance, variation + evolution~

• DNA stands for deoxyribonucleic acid and is the genetic material of all living things.
• Your DNA determines what inherited characteristics you'll have.
• DNA is found in the nucleus of animal and plant cells in structures called chromosomes.
• Chromosomes usually come in pairs.
• DNA is a naturally occurring polymer. It is made of two strands coiled together in a double helix structure.
• Genes determine your physical appearance (eye colour) as well as other traits like blood type or susceptibility to certain diseases
• A gene is a small section of DNA found on a chromosome.
• Each gene codes for a particular sequence of amino acids which are put together to make a specific protein.
• DNA determines what proteins the cells produces eg. haemoglobin, keratin. This determines what type of cell it is.
• The genome is the entire set of genetic material in an organism.
• Understanding the human genome is important because:

  • It allows scientists to identify genes linked to diseases
  • This could help to develop treatments
  • Allows scientists to trace the migration of different groups in history eg. from the common ancestor who lived in Africa
• DNA strands are polymers made up of repeating units called nucleotides.
• Each nucleotide consists of a sugar, a phosphate groups and a base.
• DNA is made of four bases:

  • A pairs with T
  • C pairs with G
• The order of bases in a gene decide the order of amino acids in a protein.
• Each amino acid is coded for by a sequence of three bases. These are joined together to make various proteins.
• Non-coding DNA switches genes on and off, controlling whether a gene is expressed or not.
• Proteins are made in the cytoplasm on structures called ribosomes.
• To make proteins, ribosomes use the code in the DNA. The DNA is too large to exit the nucleus, so molecules called mRNA copy the code from the DNA and act as messengers between the DNA and the ribosomes.
• The correct amino acids are brought to the ribosomes in the correct order by carrier molecules.
• When a chain of amino acids has been assembled, it folds into a unique shape which allows the protein to perform the task it needs to do.
• Examples of proteins are:

  • Enzymes
  • Hormones
  • Structural proteins eg. collagen
• A mutation is random change in the DNA of an organism.
• The chance of a mutation is increased by exposure to certain substances and some types of radiation.
• Mutations change the sequence of the DNA bases in a gene, which produces a genetic variant. Mutations in a gene sometimes lead to changes in the protein it codes for.
• Most mutations have little to no effect on the protein. However, some mutations could seriously effect how a protein carries out it's function (like changing the shape of an enzyme's active site). If there is a mutation in non-coding DNA, it can alter how genes are expressed.
• There are three different types of mutation:

  • Insertion - when a new base is inserted. Has a knock-on effect on bases further down the sequence
  • Deletion - when a random base is deleted. Have a knock-on effect like insertions
  • Substitutions - when a random base is swapped for another one.