1. Mutation: DNA changes DO NOW: 3/12 Objective:
Define mutation, identify several types, and describe their effect on organisms.
Task:
If all mRNA molecules begin with the sequence AUG, what DNA sequences might be the beginning of a gene?

2. 5’ ATG CCC CAT 3’ 2 possibilities, in RED
Read as a coding strand (5’3’) ATG transcribed to AUG.
Read as a template strand (3’5’), TAC translates to AUG.

3. UPDATE! Bio3: FlyDay VI, Seminar TOMORROW
Reports due at end of seminar
Pedigrees
Squares
Conclusions
Handouts
Show up prepared to defend your results and think on your feet!

4. Back to the DNA… Refresher:
Replication
Transcription
Translation
DNA
mRNA
Protein

5. Transcription: DNA  mRNA
The information carried by DNA is copied into mRNA form by the enzyme RNA polymerase (and others).
Translation: mRNA  Protein
The information carried by mRNA is translated into a sequence of amino acids. This requires a ribosome (containing rRNA) and tRNA to bring the correct amino acids to the mRNA

6. DNA changes
Sometimes, a gene can be “turned on” (induced, or activated) and cause a protein to be made, while at other times it can be “turned off” (inhibited or repressed) to save energy - like a light bulb
Genes also change over time, like people do. A mutation is a change in a DNA sequence.

7. MUTATION: A Change in a DNA Sequence
Any change to a DNA sequence is a mutation.
Therefore, a MUTANT is an organism with a DNA sequence that has changed… meaning all of us!
Very few mutations are advantageous, some are harmful, but most make no difference at all (silent mutations), since about 90-95% of your DNA does not code for proteins.
Note: only mutations present in gametes can be passed on to offspring!

8. Pop-Culture Mutants?

9. Definitely Not This One…

10. Mutation Causes
Replication errors (about 1/108, 1/1010 after error correction)
Mutagens
Chemicals that modify or mimic bases
Radiation
Retroviruses, transposons, gene splicing.
Base analogs: 5-bromo-uracil can replace thymine in DNA, causing mutations because it can base-pair with guanine

11. Mutations Cause Variation in Populations
Mutation produces new alleles that can give organisms new characteristics.
Variation is ESSENTIAL for evolution to take place.

12. Mutant Flies

13. Gene Splicing and Transgenic Organisms
Gene splicing is when genes from two or more organisms are combined to make a transgenic organism
RECOMBINANT DNA: A DNA molecule with information from 2 or more organisms.

15. Mutation Type 1
Genome Mutations (nondisjunction): a change in chromosome number. Always serious, often lethal.

16. Mutation Type 2: Chromosomal Mutations
Chromosomal mutations affect large pieces of chromosomes. Their effects vary. Examples: Deletion (A) Inversion (B) Translocation (C) Duplication (D)

17. Mutation Type 3: Single Gene Mutations
As the name implies, single gene mutations affect only a single gene. .

18. Types of Single Gene Mutations
Deletions: One or more bases is removed from a sequence.
ATTAGG becomes ATGG
Insertions: One or more bases is added.
ATTAGG becomes ATTAAGG
Point Mutations: One or more bases is replaced with a different base
ATTAGG becomes ATAAGG

19. More Mutation Examples
Missense: (point mutation)
The cat ate the rat  The cat ate the hat
Nonsense: (new stop signal)
The cat ate the rat  The cat ate
Frameshift: (insertion or deletion changes reading frame)
The cat ate the rat  Ath eca tat eth era t.

23. Mutations that Matter Most mutations have no effect.
Those that do have an effect are usually bad:
Cancer
Loss of function (protein doesn’t work anymore)
A tiny fraction of a fraction have a positive effect
Increased survival & reproduction (Michael Phelps Marfan Syndrome, etc…)

24. Do you have it? A mutation is: When a gene is turned on
When a gene is turned off
A change in a DNA sequence
Always bad for the organism that has it

25. Do you have it?
These types of mutations are the most serious because they can change the whole protein structure, not just one amino acid:
Point mutations
Frameshift mutations
Insertions of 3 nucleotides
Always bad for the organism that has it

26. Do you have it?
The lac gene produces an enzyme that breaks down lactose (a type of sugar) and provides energy to a cell. The gene needs to be _____________ if lactose is to be used.
induced
inhibited
mutated
recombinant

27. Do you have it?
Mutations in which of the following cells can be passed on to offspring?
Neurons (brain cells)
Epithelial (skin) cells
red or white blood cells
Germ (gonad) cells