1. Year 10 Genetics 2 Human inheritance
Chris Willocks 2006

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

3. Heritable traits
Attached and unattached ears
Concave nose

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
AA, AO B
BB, BO O OO AB

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