Lethal Recessive Alleles 1 2 3 4 5 6 2008-2009

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

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

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

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

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

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

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

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

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

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

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

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

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

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

_____________________________ 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.

loss of one amino acid

_____________________________ 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

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

Any questions? 2008-2009