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AP Biology 2008-2009 Lethal Recessive Alleles 12 3456.

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Presentation on theme: "AP Biology 2008-2009 Lethal Recessive Alleles 12 3456."— Presentation transcript:

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2 AP Biology Lethal Recessive Alleles

3 AP Biology Vocab: Write definition and then either picture/example 1) Lethal- capable of causing death 2) Gene Pool- all the genes, including all the different alleles for each gene, present in a certain population

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

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

6 AP Biology 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

7 AP Biology 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

8 AP Biology 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

9 AP Biology Practice Problem 1: AA x AA A A A A AA A A A A 2 homozygous dominant parents

10 AP Biology Practice Problem 2: AA x Aa A A A a Aa A a AA A A 1 homozygous dominant and one heterozygote parent

11 AP Biology Practice Problem 3: Aa x Aa A a A a Aa A a A a 2 heterozygous parents

12 AP Biology Practice Problem 4: AA x aa aa A A aa a a AA A A 1 homozygous dominant, 1 homozygous recessive

13 AP Biology Simple pedigree analysis What’s the likely inheritance pattern?

14 AP Biology Simple pedigree analysis What’s the likely inheritance pattern?

15 AP Biology 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

16 AP Biology Genetic testing sequencing individual genes Test parents Test baby

17 AP Biology _____________________________ 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 - & H 2 O 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

18 AP Biology loss of one amino acid

19 AP Biology _____________________________ 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

20 AP Biology 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

21 AP Biology Any questions?


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