Multi-trait Inheritance
Example Problems:
Pg 212, #1.
Pg 214, #3.
Dihybrid Cross
A
cross involving…?
 Imagine
having a pea plant that is homozygous
purple flower (PP) and homozygous round seed
(RR)
 What
possible gametes could be produced by
this plant?
Dihybrid Cross
 Imagine
having a pea plant that is heterozygous
purple flower (Pp) and heterozygous round seed
(Rr)
 What
possible gametes could be produced by
this plant?
Law of Independent Assortment
Pp Rr
PR Pr
pR
pr
Performing a Dihybrid cross
 If
two plants cross that are both
heterozygous for purple flowers (Pp) and
round seeds (Rr)…
 What
is the ratio of possible genotypes in the
offspring?
 What
is the ratio of phenotypes in the
offspring?
Probability
 The
ratios from Punnett Squares tell us the
probability of an offspring occurring
 In
the previous cross, what is the probability
of having an offspring that has purple
flowers and wrinkled seeds?
Probability
 The
Product Law
 Definition:
 From
the previous slide, what is the
probability of having two offspring that both
have purple flowers and wrinkled seeds?
Sex Linkage
Sex-linked Genes
 X-linked
 Color
genes:
blindness, male-pattern baldness,
 Hemophilia:
 XH
is normal gene (dominant)
 Xh
is the hemophilia gene (recessive)
Sex-linked Genes
 If
a woman with hemophilia has a child
with a normal man, what is the probability
that their child will have hemophilia?
 Make
sure you can perform this punnett square.
Pedigrees
Page 199, #2
Page 201, #3-4
Pedigree
A
chart that…
 Be
able to differentiate:
Male
and female
Matings
Siblings
Who
has a disease/trait?
Pedigree
Pedigree

Hypercholesterolemia, a dominant autosomal
disease