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Year 10 Genetics 2 Human inheritance

Year 10 Genetics 2 Human inheritance. Heritable traits. Widow’s peak Cleft chin Tongue rolling. Attached and unattached ears Concave nose. Heritable traits. Blood groups. 4 blood groups – A, B, O, AB Blood group A has A antigens on red blood cells

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Year 10 Genetics 2 Human inheritance

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  1. Year 10 Genetics 2Human inheritance Chris Willocks 2006

  2. Heritable traits • Widow’s peak • Cleft chin • Tongue rolling

  3. Attached and unattached ears Concave nose Heritable traits

  4. Blood groups • 4 blood groups – A, B, O, AB • Blood group A has A antigens on red blood cells • What antigens are on the other blood groups?

  5. Phenotypes and genotypes of blood groups

  6. Blood group inheritance • Can a couple of blood groups A and B have a child with blood group O? P AO X BO Gametes (½A +½O) , (½B +½O) F1 genotypes ¼AB + ¼AO + ¼BO + ¼OO F1 phenotypes ¼AB + ¼A + ¼B + ¼O

  7. Karyotypes

  8. Pedigrees

  9. Your family pedigree • Draw your family as a pedigree

  10. Types of inheritance 4 types of inheritance: • Autosomal recessive eg Albinism • Autosomal dominant eg Huntington’s disease • Sex-linked recessive eg Haemophilia • Sex-linked dominant eg Rickets

  11. Albinism • Autosomal recessive • How can 2 normal parents have an albino child? A = normal a = albino P Aa X Aa Gametes (½A +½a) (½A +½a) F1 genotypes ¼AA + ½Aa + ¼aa F1 phenotypes ¾normal + ¼albino

  12. Albinism pedigrees • Assign genotypes to each person in the pedigrees • Let A = normal, a = albino

  13. Polydactyly • Autosomal dominant • Will a person with polydactyly pass it to their children? Let P = polydactyly p = normal P Pp X pp Gametes (½P +½p) , p F1 genotypes ½Pp + ½ pp F1 phenotypes ½polydactyly + ½normal

  14. Polydactyly pedigree • Let P = polydactyly, p = normal • Assign genotypes to the pedigree • Number the generations and individuals using the standard notation

  15. Haemophilia • Haemophiliacs lack blood clotting factors • Need clotting factors from blood donations to survive • Blood is screened to remove any viruses before being used • Many haemophiliacs were infected with hepatitis or HIV

  16. Haemophilia inheritance • Haemophilia gene is on the X chromosome • Sex-linked recessive X = normal, Xh = haemophilia P X Xh x XY Gametes X, Xh and X, Y F1 genotypes XX, X Xh , XY, XhY F1 phenotypes normal, carrier, normal, haemophiliac • Carrier females pass it to half their sons

  17. Haemophilia pedigree • Assign genotypes to the pedigree • Let X = normal, Xh = haemophilia

  18. Haemophilia in the Royal Family • Queen Victoria was a carrier for haemophilia • Due to a chance mutation. • Her children married other royalty and passed the trait throughout the royal families of Europe.

  19. Queen Victoria’s pedigree

  20. Rickets • Sex linked dominant XR = Rickets , X = normal P XR Y x XX Gametes XR, Y and X F1 genotypes XR X, XY F1 phenotypes Rickets, normal • A male with Rickets will pass it to his daughters

  21. Rickets pedigree • Number and assign genotypes • XR = Rickets , X = normal

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