1. Lethal Recessive Alleles1 2 3 4 5 6

2. Vocab: Write definition and then either picture/example
Lethal- capable of causing death
Gene Pool- all the genes, including all the different alleles for each gene, present in a certain population

3. Natural Selection
Chooses the “fittest” individual to survive have offspring
Die
Survive
Natural Selection

4. Natural Selection
Can’t work on things it cannot see! G= Green g = Blue GG
Survive
Die gg
Survive
Natural Selection
Can’t see bad allele Gg

5. Recessive diseases
The diseases are recessive because the allele codes for either a malfunctioning protein or no protein at all
Heterozygotes (Aa)
Normal
have a normal phenotype because one “normal” allele produces enough of the required protein

6. Recessive diseases
The diseases are recessive because the allele codes for either a malfunctioning protein or no protein at all
Homozygous Recessive (aa)
Lethal, Die before certain age
Lethal phenotype because neither recessive allele produce the required protein

7. Recessive diseases
The diseases are recessive because the allele codes for either a malfunctioning protein or no protein at all
Homozygous Dominant (AA)
Normal
have a normal phenotype because both “normal” allele produce the required protein

8. Practice Problem 1: AA x AA A AA A A A AA
2 homozygous dominant parents
AA x AA AA A A A AA A

9. Practice Problem 2: AA x Aa A AA A A A Aa a a
1 homozygous dominant and one heterozygote parent
AA x Aa AA A A A a Aa A a

10. Practice Problem 3: Aa x Aa Aa A a A a A a Aa A a
2 heterozygous parents
Aa x Aa Aa A a A a A a Aa A a

11. Practice Problem 4: AA x aa A AA a A a aa
1 homozygous dominant, 1 homozygous recessive
AA x aa AA A a A aa a

12. Simple pedigree analysis
What’s the likely inheritance pattern?
Simple pedigree analysis 1 2 3 4 5 6

13. Simple pedigree analysis
What’s the likely inheritance pattern?
Simple pedigree analysis 1 2 3 4 5 6

14. Genetic counseling
Pedigree can help us understand the past & predict the future
Thousands of genetic disorders are inherited as simple recessive traits
from benign conditions to deadly diseases
albinism
cystic fibrosis
Tay sachs
sickle cell anemia
PKU

15. sequencing individual genes
Genetic testing
Test parents
Test baby
sequencing individual genes

16. _____________________________
Primarily whites of European descent
strikes 1 in 2500 births
1 in 25 whites is a carrier (Aa)
normal allele codes for a membrane protein that transports Cl- across cell membrane
defective or absent channels limit transport of Cl- & H2O across cell membrane
thicker & stickier mucus coats around cells
mucus build-up in the pancreas, lungs, digestive tract & causes bacterial infections
without treatment children die before 5; with treatment can live past their late 20s
normal lung tissue
Cystic fibrosis is an inherited disease that is relatively common in the U.S. Cystic fibrosis affects multiple parts of the body including the pancreas, the sweat glands, and the lungs. When someone has cystic fibrosis, they often have lots of lung problems. The cause of their lung problems is directly related to basic problems with diffusion and osmosis in the large airways of the lungs.
People without cystic fibrosis have a small layer of salt water in the large airways of their lungs. This layer of salt water is under the mucus layer which lines the airways. The mucus layer in the airways helps to clear dust and other inhaled particles from the lungs.

17. loss of one amino acid

18. _____________________________
Primarily Jews of eastern European (Ashkenazi) descent & Cajuns
strikes 1 in 3600 births
100 times greater than incidence among non-Jews
non-functional enzyme fails to breakdown lipids in brain cells
fats collect in cells destroying their function
symptoms begin few months after birth
seizures, blindness & degeneration of muscle & mental performance
child usually dies before 5yo

19. Genetics & culture Why do all cultures have a taboo against incest?
laws or cultural taboos forbidding marriages between close relatives are fairly universal
Fairly unlikely that 2 unrelated carriers of same rare harmful recessive allele will meet & mate
but matings between close relatives increase risk
“consanguineous” (same blood) matings
individuals who share a recent common ancestor are more likely to carry same recessive alleles

20. Any questions?