Genetic Changes 11.3

Genetic Changes

DNA controls cell structure and function

What happens if nucleotide sequence is changed?

Genetic Changes

Sometimes no harm is done, tailless manx cat Some changes cause cell to behave differently,

UV rays cause cancerous cell division

Mutation

Any change in DNA sequence A mutagen is something that can cause a

change in DNA Can we name some mutagens?

Mutation

Mutagens include Radiation => x-rays, ultraviolet light, nuclear radiation Chemicals => dioxins, asbestos, benzene,

formaldehyde

Mutation

Mutations in reproductive cells Change in DNA in sperm or egg cell Could lead to new trait Could lead to a protein that

does not work correctly, the zygote may not survive

Mutation

Mutations in body cells Mutation not passed on to offspring, but could

cause problems for the individual Skin cell may lose elasticity, when the cell divides,

daughter cells also lack elasticity If mutation affects cell division, can cause cancer

Types of Mutation

Point mutation – change in a single base pair in DNA The dog bit the cat. The dog bit the car.

Types of Mutation

Frameshift mutation – a single base is added or deleted from DNA Changes all the

codons after the mutation

Types of Mutation

Chromosomal mutations – common in plants,parts of chromosomes break off, join incorrectly, crossover with the wrong chromosome Lead to nondisjunction because homologous

chromosomes cannot pair when some have extra parts

Few chromosome mutations are passed on to offspring because zygote usually does not survive, or is unable to reproduce

Types of Mutation

Chromosomal mutations Deletions Insertions Inversions Translocations

Repairing DNA

Enzymes proofread the DNA and replace incorrect nucleotides

Exposure to mutagens leads to more uncorrected mistakes