Deducing Genotypes

1
Deducing Genotypes

• Song Hee Bae
• IB1 Biology

2
Pedigree Charts

• How a trait can pass
• Whether dominant or recessive
• Whether sex-linked or not
• Sex-linkage
• Ex) color blindness, hemophilia
• Similar to family tree
• Squares male
• Circles female
• Shaded affected
• Not shaded unaffected

3
Huntingtons Disease

• Whether mothers genotype is Hh or HH
• Consider genotypes of next generation
• Affected people
• First daughter
• Forth son
• Fifth son
• Unaffected people
• Second and third sons
• Grand daughter
• Mother must be Hh

4
Using Test Crosses

• To distinguish betweenDominant X Dominant /
  Dominant X Recessive
• A subject is crossed with homozygous

w
w
W
Ww
Ww
W
Ww
Ww
ww
w
w
Ww
W
Ww
Ww
w
ww
ww
W long ears w short ears
5
Vocabulary

• Pedigree chart diagram which are constructed to
  show biological relationships.
• Sex linkage any genetic trait whose allele has
  its locus on the X chromosome.
• Test cross a method to distinguish whether the
  individuals that might have the same phenotype
  are influenced by dominant / recessive allele.

Reference

• IB Study guides page 29
• Pearson Biology SL page 105, 108109