Alternative Patterns
of Inheritance
Incomplete Dominance
• Heterozygote creates a
new phenotypic trait
that is in between the
dominant and the
recessive ( i.e. middle)
• ex. Snap dragon flowers
can be Red (RR), Pink(RW,
or white(WW) with
different allele
combinations
• Ex. Hair texture
• Curly , wavy, straight ( C, S)
Lets practice
1. Predict the
genotypes and
phenotypes of a
cross between a
red snapdragon
and a pink snap
dragon
2. Predict the
genotype and
phenotypes of a
cross between 2
individuals with
wavy hair.
Co- Dominance
• In the heterozygote,
both alleles are
expressed at the
same time.
• Example: Coat color in
the horses can be red (
RR), white (WW), or
Roan ( RW).
• Roan = both red and
white hairs in the coat
color at the same time
Lets practice
1. Predict the
genotypes and
phenotypes of a
cross between a
White cow and red
cow.
2. Predict the
genotype and
phenotypes of a
cross between 2
individuals from
the F1 generation
from question #1
Multiple Alleles
• Traits are controlled by more than 2
alleles
• Ex Blood type uses 3 alleles (IA, IB, i)
• Which alleles do you think are dominant?
• Which alleles are recessive?
• Would any of theses alleles demonstrate
an alternative pattern of inheritance?
What are the different blood types?
Type A
Type B
Type AB
Type O
• What would be the
genotypes for those
phenotypes?
• IAIA or Iai
• IB IB or Ibi
• IAIB
• ii
Let’s Read about how blood type
influences some cultures… And answer
the questions.
Make sure your blood type
article is complete so that we
can grade
• Also Make sure that
your practice punnett
squares worksheet is
complete .
• We will go through
both of these… today
and take more notes
ABO SYSTEM is NOT THE
ONLY ONE
+
Rh
Rh
OTHER BLOOD TYPES
NO PROBLEMS
____________________
IF:
Rh+
MOM is _____
+
Rh
& BABY is _____
Image modified from:
http://www.wsd1.org/lessonplans/images/Body.gif
+
Rh
MOM is _____
& BABY is ____
Rh-
Can be a ___________ IF:
PROBLEM
Rh
Mom is _____
Baby is _____
Rh+
1st baby OK but few baby cells
entering mom’s bloodstream
put mom’s immune system on
alert for + cells.
Next + baby, mom’s immune
system can attack baby as it is
growing
Mom given shot after 1st birth
prevents this
Image modified from:
http://www.wsd1.org/lessonplans/images/Body.gif
Homework
• Complete the punnett squares practice work sheets
WARM UP
• COMPLETE THE INCOMPLETE AND CO-DOMINANCE
WORKSHEET
• Only answer #s 6-9, 11, 14, 19
• Complete the problems on a separate piece of paper.
Sex Linked Traits
• Sex linked traits – when genes
are carried on the
•
Some Examples of sexlinked traits…
When setting up a punnett
square…
• The sex linked trait is written as a lowercase letter because they are
recessive and also a super script
• Example
• The phenotypes for sex linked crosses must include the gender of
the offspring and whether or not they have the trait
• Phenotypes for baldness traits..
= normal female
= normal male
= carrier female
= bald female
= bald male
Let’s Practice
• A bald man marries a
normal female. Determine
the phenotypic ratio for
the offspring.
- A bald male marries a
carrier female. What are
the chance that all the
children will be bald?
Polygenic Traits
• Traits are controlled by several genes. Ex. Skin, eye, and hair
color are controlled by more than one gene.
Pedigree – shows
patterns of inheritance
• Individuals either have the trait, do
not have the trait, or are a carrier
for the trait
• Carrier = individual who has ONE
copy of a recessive allele
DRAW and LABEL THE PEDIGREE
ACCORDING TO THE FOLLOWING SCENARIO:
Han Solo, son of Owen, and Leia, daughter of
Anikin, both have freckles, but their son Jedd
does not. Queen Amadala, died giving birth
to twins, Luke and Leia. Leia has freckles, but
her brother does not. Han’s brother, Chewie,
and his sister, Padme, like their mother, Peru,
do not have freckles.