BIO 325 Study Guide - Midterm Guide: F1 Hybrid, Consanguinity, Zygosity
Pedigree For a Recessive Disease
• Signatures of a recessive trait occurs rarely unless consanguineous
• Infer about genotype: homozygous recessive cc for disease; heterozygous Cc both
parents are carrier
o Assumption for a disease allele is rare, assume that all individuals are
homozygous normal unless there is evidence
o Rare is likely a disease allele came from a single orgin
• Recessive alleles – cystic fibrosis
o CC, Cc = normal
o cc = disease
Pedigree For a Dominant Disease
• Dominant alleles – Huntington disease
o HH, Hh = disease
o Hh = normal
• Assumption for disease allele is rare, assume all individuals are homozygous normal
o For dominant, diseased individual is heterozygous Hh x hh
Recognizing Recessive Traits in Pedigrees
• 4 keys aspects of pedigrees with recessive traits
o Affected individuals can be the children of 2 unaffected carriers as a result of
consanguineous matings
o All the children of 2 affected parents should be affected
o Rare recessive traits show a horizontal pattern of inheritance
o Recessive traits may show a vertical pattern of inheritance if the trait is
etreel coo i the populatio
Recognizing Dominant Traits in Pedigrees
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