Mutation—change in the structure of DNA

--may cause changes to physical traits or how body parts function

*Sometimes the wrong code is copied when DNA is replicated

--if change is permanent, then the mutation will become part of each cell; each cell will carry the mutation as the cells replicate

--may cause proteins to be made incorrectly and affect how well they work

*Mutations may be good, bad, or neutral

*good increase chance of survival; bad decrease chance of survival

Neutral (not good or bad) example: heterochromia (each eye is a different color)

Good example: humans can see more colors than some animals (still less than others)

--helps us to see prey and predators, and to identify good/bad foods

Bad example: Sickle cell: blood cells are the wrong shape, reduce ability to carry oxygen

*Some depend on the organism and the environment:

Albinism: mutation of gene for melanin (produces color in skin and eyes)

--results in no melanin production = white skin

--bad for alligators—can’t sneak up on prey in swamps

--bad for rabbits in forests—hard to hide from predators

--good for rabbits in snow—easy to hide from predators

Causes of mutations

*Errors in DNA replication

--insertion—piece of one chromosome misplaced inside a difference chromosome

--deletion—piece of a chromosome is lost/disappears

--substitution—one base is replaced by a different base in the DNA

*Spontaneous mutation—base is chemically changed or lost

*Mutagens (outside factors in the environment that can change genes)

--If DNA is damaged, body tried to guess the correct matching base, but can be wrong

--chemicals (like tobacco smoke) can alter genes (cause lung cancer, etc)

--UV (sun) and other types of radiation can alter genes (cause skin cancer, etc)