1. Take out CHNOPS activity
No Warm-Up Today
Take out CHNOPS activity

2. Section 12.4 (Causes, Examples)
DNA Mutations!
Section 12.4
(Causes, Examples)

3. What is a Mutation? Mutation: DNA is changed Occurs because of:
Incorrect copying in DNA synthesis
Incorrectly made mRNA strand in transcription
Outside radiation, etc. disrupts DNA
Can be gene or chromosomal mutations

4. Gene Mutations
Change to one or a few nucleotides on a gene (segment) of DNA
Point mutation
- Substitution: put an ‘A’ instead of a ‘G’, etc.
- Substitutions disrupt one amino acid
- Substitutions rarely cause a genetic disorder as proteins can still function with only one incorrect amino acid

5. Sickle Cell Anemia
In Sickle Cell Anemia, a substitution has occurred on chromosome 11 so that the protein hemoglobin is made incorrectly
Distorts shape of red blood cells so they can’t carry oxygen well
Most common in tropical areas as
this mutation actually prevents
malaria (Plasmodium can’t infect
sickle shaped cells)

6. Gene Mutations Insertion or Deletion are ‘Frameshift Mutations’
By inserting/deleting a nucleotide, the 3 letter mRNA reading system is shifted by one letter
Therefore, every amino acid is incorrect and the entire protein is useless
More common cause of genetic disorders
If this mutation is in a developing fetus, every cell makes the incorrect protein!

7. Gene Mutations: Frameshift

8. Cystic Fibrosis
Caused by insertion of two letters in the CFTR gene on chromosome 7
Causes cells to secrete thick, sticky mucus that impedes lung function
Usually fatal
1 in 1600 Caucasians
have CF; 1 in 29 carry
the recessive gene

9. Tay Sachs Disease
The HEXA gene on chromosome 15, which makes an enzyme that breaks down extra lipids, is ineffective due to
a deletion
Extra lipids build up in brain cells, impairing motor function and causing death
1 in 5000 have the disorder;
1 in 250 are carriers
1 in 27 people of Jewish descent are carriers

10. Chromosomal Mutations
Change in number or structure of whole chromosome
Example: People with Down Syndrome have an extra chromosome 21 in every cell

11. Effects of Mutations Most mutations are non-harmful
Some mutations increase genetic variation in a population, helping them survive better!
Pandas have a ‘thumb’
that is an enlarged wrist
bone from a mutation
Those with the mutation
survived better because
they could hold bamboo!

12. How are mutations inherited?
One or both parents will carry a ‘mutant gene’ that causes a disorder
If this gene is ‘recessive’ they don’t have the disorder but are carriers
If this gene is ‘dominant’ they have the disorder
In chromosomal mutations, one parent gives an extra chromosome, mutant chromosome, or doesn’t give one at all

13. If both parents are carriers, the baby has the disorder and they don’t!

14. How are mutations inherited?
The gene is carried in the sperm or the egg and passed on to the offspring when the egg is fertilized
Parents don’t know if the baby has the disorder until it has health problems from the incorrectly made proteins
Is there some way to prevent embryos from having genetic disorders?

15. Preventing Genetic Disorders in Embryos…and beyond?
“Designer Babies”
Preventing Genetic Disorders in Embryos…and beyond?

16. Creating and Screening Embryos
Through In-Vitro Fertilization, human embryos can be created and analyzed in a lab
In Vitro = egg and sperm are harvested from parents, fertilized, and implanted back in the mother

17. Creating and Screening Embryos
A single cell can be removed from an 8 day old embryo before it is implanted
The cell is analyzed for gender and 200+ identified genetic disorders
The DNA of the embryo’s cell is run through a computer program that compares the sequence to ‘normal’ genes to identify a disorder

18. What‘s legal? What’s ethical?
It is currently legal in the U.S. to screen for genetic disorders and gender and to choose embryos based on the outcome
Not restricted to only couples carrying genes for genetic disorders
Should it be?
Are we headed down the slippery slope of designing our children?

19. Reading Assignment
With your table partner, determine who is the stronger/faster reader
The stronger reader takes the “Brave New Babies” article and the other person takes the “Outcry” article
Read and answer these questions on notebook paper:

20. Reading Assignment
What are scientists capable of doing in regard to human embryos?
What are the benefits?
What are the drawbacks?
Should PGD (pre-implantation genetic diagnosis) be allowed for everyone? Why or why not?