DNA Mutations

Section 11.3

Review

• DNA controls structure and function of cells because it holds the code to build all proteins.

DNA

transcription translation

mRNAAmino acid sequence

Mutation—mistakes in the DNA

• Mistakes can occur randomly through errors in replication, transcription, or cell division.

• External factors can also cause mutations.

• Mutations can occur in reproductive cells (sperm or egg) or in body cells.

Only adult cells affectedOnly offspring affected

New protein that is better than before

New protein hurts organism or doesn’t work at all.

Mutation in body cellMutation in

sperm or egg

Cell may no longer work properly

Cell doesn’t reproduce properlymay lead to cancer

Certain types of mutations are found in the genes or DNA

• Point (substitution) mutation is the change in a single base pair.– EX. When you change one letter in a

sentence:• THE DOG BIT THE CAT.• THE DOG BIT THE CAR.

DNA mutations con’t

• Frameshift mutation is when one base is deleted or inserted and the whole sequence shifts.– EX: If you delete the letter G, from the original

sentence: • THE DOG BIT THE CAT.• THE DOB ITT HEC AT.

– EX: If you insert the letter A, into the sequence.

• THE DOG ABI TTH ECA T.

Chromosomes carry large amounts of genetic material and can also have

mutations

Mutation causes are called mutagens.

• Radiation (nuclear, x-ray, UV, etc), asbestos, formaldehyde all can lead to mutations.

• Organisms have evolved several enzymes that check and repair DNA, but the more exposure to a substance, the more chances for mistakes.