5.2 Mutations

6.2 MutationsPages 234-239 Mutations can be caused by:- environmental agents - errors during cell divisionRadiationExposure to radioactive materials can cause genetic mutations.

ChemicalsExamples: Nitrosonguanidine (NTG), Hydroxylamine, Bromodeoxyuridine (BrdU), and Ethidium bromide

EffectsPositive, negative or neutral effect on phenotype or cell deathPoint MutationsA failure of the genetic machinery to copy the DNA perfectly.Base-pair substitutionThe wrong nitrogenous base pair is included.

InsertionExtra nitrogenous bases are included during the copying of the DNA.

DeletionsOne or more base pairs are left out during the copying of DNA

Chromosome mutationsInvolve the entire chromosome or major chunks

Non-disjunction (sister chromatids fail to separate during meiosis)Down syndromeTurner syndromePatau syndromeChromosome mutationsLarge scale deletions, insertions, duplications or inversions (flipping) of entire portions of a chromosome

Inheriting mutationsThe genetic machinery is designed to find and fix copying errors. (less successful with age)

Inheriting mutationsMost of the DNA does not code for genes (so errors here are meaningless)

Inheriting mutationsMutations in autosomes are not passed on to the next generation

Inheriting mutationsMutations in sex cells can be passed on to the next generation

Dominant vs. RecessiveMutations can be dominant and appear in the first generation. Ex. Huntingtons disease

Mutations can be recessive and appear only rarely when two individuals with the same mutation produce offspring. Ex. Cystic FibrosisSickle cell anemiaMisshapen red blood cells can cause pain and an increased risk of infection

Sickle cell anemiaMalaria parasite enters red blood cell causing it to become sickle-shaped and leading to its destruction and removal.Lactose ToleranceMost babies tolerate lactose producing the enzyme needed to digest their mothers milk75% of adults do not tolerate lactose25% of adults have a mutation in their genes that allows them to digest lactose.Spontaneous mutationsHappen by accident

Induced mutationsResult due to exposure to a physical or chemical agent

Antibiotic ResistanceUsually antibiotics kill bacteria by weakening their cell wall.Mutations in genes that code for the cell wall allow the bacteria to be resistant to antibiotics.Jumping GenesTransposons are segments of the DNA that can move from place to place.

Transposition is the act of moving a segment of DNA from one place to another.Example: Indian corn

hemophiliaA transposon can insert itself into a gene for normal blood factor VIII, causing hemophilia in boys (X-linked gene).Microarray TechnologyMicroarray-small membrane or glass slide -contains samples of hundreds or even thousands of DNA fragments-arranged in a regular pattern. -Each fragment corresponds to a geneMicroarray