Year 10 Genetics 2 Human inheritance Chris Willocks 2006

Heritable traits Widow’s peak Cleft chin Tongue rolling

Heritable traits Attached and unattached ears Concave nose

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?

Phenotypes and genotypes of blood groups AA, AO B BB, BO O OO AB

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

Karyotypes

Pedigrees

Your family pedigree Draw your family as a pedigree

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

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

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

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

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

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

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

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

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.

Queen Victoria’s pedigree

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

Rickets pedigree Number and assign genotypes XR = Rickets , X = normal