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Mendel and Human Traits

Mendel and Human Traits. Mendelian Inheritance. Heterozygous and Homozygous Dominant have the same phenotype Homozygous recessive will have a different phenotype. Intermediate Inheritance (Incomplete Inheritance) . The heterozygote is an intermediate of the two homozygotes

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Mendel and Human Traits

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  1. Mendel and Human Traits

  2. Mendelian Inheritance • Heterozygous and Homozygous Dominant have the same phenotype • Homozygous recessive will have a different phenotype

  3. Intermediate Inheritance (Incomplete Inheritance) • The heterozygote is an intermediate of the two homozygotes • Red (RR) X White (WW) • Pink (RW) RR WW RW

  4. Pink Flower Ex. • RR - Red • WW - White • RW - Pink • All Offspring are pink R R W W

  5. Pink Flower Ex.(cont.) • RR - Red • WW - White • RW - Pink • 1/4 = Red • 1/2 = Pink • 1/4 = White R W R W

  6. Codominance • Sickle Cell Anemia • Blood cells are shaped like a sickle or half-moon • The sickled cells cause clots • Heterozygotes have some normal and some sickled cells • SS = Sickeled cells • RR = Regular cells • SR = Some regular, some sickled S S R R

  7. Sometimes there are more than two alleles for each trait Ex. Blood types A B O AB The alleles: A = IA B = IB O = i Multiple Alleles

  8. Multiple Alleles (cont.) • Blood type is determined by the surface proteins on a blood cell • Proteins are determined by what alleles the person has

  9. Multiple Alleles (cont.) A AB B O

  10. Multiple Alleles (cont.)

  11. Multiple Alleles (cont.) IA i • Can a man with type A blood and a woman with type AB blood have a daughter with type B blood? IA IA IA IB IA IB

  12. Inheritance in Humans

  13. Pedigrees • A family tree that records and traces traits in a family

  14. Gender • Gender • Males = Squares • Females = Circles • Relationship • A line connecting = marriage

  15. Relationships • Vertical lines = parents to children • Each row = one generation • Roman numerals (I,II,III, etc.) • Individuals (1,2,3,4, etc.) • Slash = death

  16. Phenotype • Shaded circle of square = A person who has the trait being studied • Unshaded = Does not have trait • Half-shaded = carrier or heterozygote

  17. Practice

  18. Answers Parents I 2 1 II Children/Siblings 2 1 3 Death

  19. Used to determine genotype Shaded = attached earlobes (recessive trait) Label the genotypes! F = free earlobes, f = attached earlobes

  20. Ff Ff Ff Ff F? ff F ? Ff F ? Used to determine genotype Shaded = attached earlobes (recessive trait) Label the genotypes! F = free earlobes, f = attached earlobes

  21. Ff Ff Ff Ff F? ff F ? Ff F ? Can predict offspring Genotype • What is the percent chance that the next child in generation III will have attached earlobes?

  22. Use a Punnett Square F f 25% chance for attached earlobes F f

  23. Diseases caused by recessive alleles • Cystic Fibrosis • Defect in cell membrane protein • Develop a thick mucus in lungs and digestive tract • Tay-Sachs • No enzyme that breaks down lipids • Lipids build up nervous tissue => Brain damage • Phenylketonuria (PKU) • No enzyme to change phenylalanine into tyrosine • Build up of phenylalanine => Brain Damage

  24. Dominant Allele diseases • Huntington’s Disease • Braek down of brain tissue • Achondroplasia • A form of dwarfism • Some forms of blindness

  25. Dominant Disorders • Most of the diseases caused by dominant alleles are lethal in Heterozygotes • The individuals die before they can reproduce • Low frequency of these alleles (<99.99%)

  26. Recessive Disorders • Recessive alleles are not lethal in heterozygotes • Will be passed on from generation to generation • Only homozygous recessive individuals are affected.

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