1. mutations

2. Title the notes: Mutations Notes Add subject heading in the left hand margins. When we are finished taking notes, re-read the notes and write a brief summary of what you learned.

3. ? elephant eleqhant
The sequences of bases in DNA are like the letters of a coded message. If one or more of the bases were changed accidentally, would the cell still understand its meaning?
For example: We know that the word ELEPHANT means an animal with a trunk. But if the P were changed to a Q, ELEQHANT would be meaningless. 

4. Now and then cells make mistakes in copying their own DNA, inserting the wrong base or even skipping a base as a strand is put together. These variations are called mutations. Mutations are changes in genetic information that can cause proteins to be made incorrectly.

5. A change in one or more DNA bases will be transcribed into an incorrect mRNA sequence, which could then be translated into an incorrect sequence of amino acids.

6. In a substitution, one base is changed to a different base
In a substitution, one base is changed to a different base. Substitutions occur at a single point in the DNA sequence so they are also known as point mutations. Substitutions usually affect no more than a single amino acid, and sometimes they have no effect at all, as amino acids have more than one codon that can code for it.

7. For example:
BEFORE MUTATION
AFTER MUTATION
DNA
GGGAAACCC
AGGAAACCC
mRNA
Amino Acid

8. For example:
BEFORE MUTATION
AFTER MUTATION
DNA
GGGAAACCC
AGGAAACCC
mRNA
CCCUUUGGG
UCCUUUGGG
Amino Acid
PRO – PHE - GLY
SER – PHE - GLY
This mutation would cause an incorrect amino acid sequence, with serine replacing proline.

9. BEFORE MUTATION
AFTER MUTATION
DNA
GGGAAACCC
GGAAAACCC
mRNA
Amino Acid

10. BEFORE MUTATION
AFTER MUTATION
DNA
GGGAAACCC
GGAAAACCC
mRNA
CCCUUUGGG
CCUUUUGGG
Amino Acid
PRO – PHE - GLY
Although a mutation occurred in this scenario, this mutation had no effect, as CCC and CCU code for the same amino acid, proline.

11. In an insertion, one base is inserted or added into the DNA sequence.
BEFORE MUTATION
AFTER MUTATION
DNA
TACGCATGGAAA
TACAGCATGGAAA
mRNA
Amino Acid

12. In an insertion, one base is inserted or added into the DNA sequence.
BEFORE MUTATION
AFTER MUTATION
DNA
TACGCATGGAAA
TACAGCATGGAAA
mRNA
AUGCGUACCUUU
AUGUCGUACCUUU
Amino Acid
MET – ARG – THR - PHE
MET – SER – TYR - LEU

13. In a deletion, one base is deleted or removed from a DNA sequence.
BEFORE MUTATION
AFTER MUTATION
DNA
TACGCATGGAAA
TACCATGGAAA
mRNA
Amino Acid

14. In a deletion, one base is deleted or removed from a DNA sequence.
BEFORE MUTATION
AFTER MUTATION
DNA
TACGCATGGAAA
TACCATGGAAA
mRNA
AUGCGUACCUUU
AUGGUECCUUA
Amino Acid
MET – ARG – THR - PHE
MET – VAL – PRO - ?

15. Insertions and deletions are also called frameshift mutations because they shift the “reading frame” of the genetic message. By shifting the reading frame, frameshift mutations can change every amino acid that follows the point of the mutation.

16. The effects of mutations on genes vary widely
The effects of mutations on genes vary widely. Most mutations have little or no effect on the expression of genes or the function of the proteins for which they code.

17. Some genes negatively disrupt gene function by dramatically changing protein structure or gene activity.

18. However, some mutations produce beneficial variations
However, some mutations produce beneficial variations. Without mutations, organisms could not evolve, because mutations are the source of genetic variability in a species.

19. Examples of Harmful Mutations: some cancers, sickle cell anemia
Examples of Helpful Mutations: Chemical resistance to pesticides for insects, crops can be altered and strengthened by controlled mutations