The DNA Connection

DNA Deoxyribonucleic acid Genetic material that carries information about an organism and is passed from parent to offspring. 1953: Watson and Crick figure out the structure of DNA (double helix).

The Genetic Code Genes control the production of proteins. Proteins determine: Size Shape Color Many other traits of an organism

Structure of DNA Looks like a twisted ladder Two sides of the ladder: Made up of alternating molecules of deoxyribose and phosphates Each rung is made up of a pair of molecules called nitrogen bases.

Genes and DNA DNA molecule – made up of 4 nitrogen bases Adenine (A) and Thymine (T) Guanine (G) and Cytosine (C) (A) only pairs with (T) (G) only pairs with (C)

Mutations Any change in a gene or chromosome Mutation – Latin word that means “change”

What happens when a mutation occurs? Organism’s trait, or phenotype, may be different from what it normally would have been.

Three Types of Mutations Substitution – One base pair is substituted for another Deletion – One base pair is removed Addition – One base pair is added

Effects of Mutations A mutation is harmful if it reduces the organism’s chance for survival and reproduction. Example: white lemurs

Effects of Mutations Helpful mutations improve an organism’s chances for survival and reproduction. Example: Antibiotic resistance in bacteria.

Think about it! We can use DNA to catch criminals. Should Americans be forced to give DNA samples so everyone is on file to make it easier to catch criminals?