Mutations Mutations are changes in DNA Mutations are changes in DNA These can occur in: These can occur in: Somatic cells – can cause tumours/cancersSomatic cells – can cause tumours/cancers Germ-line cells – can cause genetically inherited disorderGerm-line cells – can cause genetically inherited disorder Spontaneous mutations – have no known cause Spontaneous mutations – have no known cause Induced mutations – have a known cause Induced mutations – have a known cause Agents that cause mutations are called ‘mutagenic agents’ Agents that cause mutations are called ‘mutagenic agents’

Mutagenic Agents Some known mutagenic agents include: Some known mutagenic agents include: Radiation (x-ray, UV, nuclear)Radiation (x-ray, UV, nuclear) Some chemical substances (formaldehyde, mustard gas, peanut oil)Some chemical substances (formaldehyde, mustard gas, peanut oil)

Types of Mutations Substitution – one nucleotide replaces another Substitution – one nucleotide replaces another Addition – one or more nucleotide is inserted into the code without one being removed Addition – one or more nucleotide is inserted into the code without one being removed Deletion – removal of one or more nucleotides without replacement Deletion – removal of one or more nucleotides without replacement

Substitution mutation This is called a point mutation because the error only occurs at the site of mutation it is not carried on afterwards

Addition and Deletion mutation Addition and deletion mutations usually result in an error at the point where the mutation occurs as well as every triplet that occurs afterwards This is called a frameshift mutation

Some mutations cause more severe effects than others Somatic cell mutations – only affect the individual not the next generation Somatic cell mutations – only affect the individual not the next generation Germ-line mutations are able to be passed on to the following generations Germ-line mutations are able to be passed on to the following generations

Some mutations cause more severe effects than others Mutations only cause problems when they alter the genetic code Mutations only cause problems when they alter the genetic code Results in production of: Results in production of: Abnormal proteinAbnormal protein Incomplete proteinIncomplete protein Some mutations can affect promoter regions causing: Some mutations can affect promoter regions causing: Reduced protein productionReduced protein production No protein productionNo protein production

What do you notice about the number of codons per amino acid? Is it possible for a mutation to occur without affecting protein production?

What type(s) of mutation are likely to cause the most severe effects? Why?

DNA repair There are a number of enzymes that are capable of repairing damage to DNA There are a number of enzymes that are capable of repairing damage to DNA In addition, NK T cells are able to destroy cells that appear to contain genetic mutations, preventing them from being replicated In addition, NK T cells are able to destroy cells that appear to contain genetic mutations, preventing them from being replicated