Download Human Genetics

Human Genetics
Multiple Alleles
- More than two alleles are used to display a specific trait
Example: Blood Types in Humans
Phenotype/ Blood Type
Genotype
A
IaIa or Iaio
B
IbIb or Ibio
AB
IaIb
O
ioio
(A and B alleles dominate over the recessive O. But together they represent co dominance.)
Punnett Square: Cross a Parent who is Heterozygous type A with a parent who is Type AB
Parents:
Iaio X IaIb
Ia
Io
Ia
IaIa
Iaio
Ib
IaIb
Ibio
Phenotype: 50% Type A
25 % Type B
25% Type AB
Sex-linked Traits
- Genes found on the X chromosome but not on the Y.
- XX = Female
- XY = Male
Example: Hemophilia- a condition where the affected individual’s blood lacks the materials
need for blood to clot if a blood vessel is broken.
Phenotype/ Gender
Genotype
Hemophiliac Male
XhY
Normal Male
XH Y
Hemophiliac Female
XhXh
Normal Female
XH XH
or XHXh
Punnett square: Cross a Hemophiliac male with a Heterozygous Normal Female.
Parents: XhY x XHXh
Xh
Y
XH
XH Xh
XH Y
Xh
XhXh
XhY
Phenotype:
Boys – 50% Normal; 50% Hemophiliac
Girls – 50% Normal; 50% Hemophiliac