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