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Deducing Genotypes. Song Hee Bae IB1 Biology. 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.
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Deducing Genotypes Song Hee Bae IB1 Biology
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
Huntington’s Disease • Whether mother’s 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
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
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, 108~109