Download Genetics - Canton Local Schools

Genetics
Test cross
• Individual of unknown genotype is
crossed with a homozygous recessive
individual
• Determine the genotype of an individual
whose phenotype is dominant
Complete Dominance
• Complete Dominance – one allele
completely dominant over the other
Incomplete Dominance
• Incomplete dominance – two or more
alleles influence the phenotype resulting
in a phenotype intermediate between
the dominant and recessive traits
• R=red r=white
Rr  pink
Codominance
• Codominance – both alleles for a gene
are expressed in a heterozygous
offspring – neither is dominant or
recessive
• Rr  red & white polka dots
Multiple alleles- 3 or more
alleles of the same gene
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Blood Types
IA
IB
or
IAIA
or
IBIB
IAIB
=
ii
=
i
IAi =
Blood type A
IBi =
Blood type B
Blood type AB
Blood type O
Sex- linked inheritance
• Traits controlled by genes located on the sex
chromosomes
• X-linked gene
• Y-linked gene
• X-linked traits more common in males
Sex-Influenced Inheritance – traits affected by
how much sex hormones are present