Transcript AC Types of Dominance

Complete Dominance
• Complete dominance:
the allele that is
regarded as dominant
completely masks the
effect of the allele that
is recessive.
• Dominant alleles are
written with capital
letters and recessive
alleles are written with
lower case letters.
For example, purple flowers are
dominant to white flowers. A
homozygous white flower is crossbred
with a homozygous purple flower. What
are the phenotypes of the offspring?
Incomplete Dominance
Incomplete Dominance:
Both alleles are capitals because the alleles are not
dominant or recessive
**neither one takes over or hides ….not dominant or
recessive…they MIX TOGETHER! Like mixing paint!
The outcome is in-between!!
R=Red Flowers B=Blue Flowers
RR=Red Flowers BB=Blue Flowers
RB=Purple Flowers
Here’s one where red and white make pink
Try These Punnett Squares…please
• Cross a Blue flower with a red flower.
• Cross a red flower with a purple flower.
• Cross two purple flowers.
Codominance
• Same deal with the alleles…all letters will be capital.
• This time they are both being dominant.
• It’s like splattering one color on another-they both show up
equally dominant.
• For example, you have a homozygous black feathered
chicken who mates with a homozygous white feathered
chicken. Their offspring will have BOTH white and black
feathers.
• Results in a third phenotype: speckled.
So…Codominant Alleles
R=Red Fish
RR=Red Fish
B= Blue Fish
BB=Blue Fish
RB=Red and Blue Fish (like spots or stripes)
Now Try These Punnett Squares…please
• Cross a Blue fish with a red fish.
• Cross a red fish with a red and blue fish.
• Cross two red and blue fish.
Blood Type is also Codominant
• Blood types A and B are
codominant.
• When present, they are
both expressed.
• However, Blood type O is
recessive.
• When present with
dominant alleles, it is
masked.
Blood Type Examples
• A man with AB blood is married to a woman
with AB blood. What blood types will their
children be and in what proportion?
• A woman with type A blood (genotype: AO) is
married to a type B person (genotype: BO).
What blood types will their children have?
Can You Pick Out the Co-dominant and
Incompletely dominant Example?
Silly Question…of course you can
See…You Did it
Sex-linked
• Sex-linked traits are carried on the sex chromosomes.
• The sex chromosomes are 23 pair.
XX = female
XY = male
Because, males only have one X chromosome, they have a much
greater chance of having sex-linked traits.
Examples of Sex-Linked Traits
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Colorblindness
a problem with the
color-sensing cones in
the retina of the eye.
You can’t see certain
colors
Red/Green-most
common
Blue Yellow
Achromatopsia-see
greys only
Hemophilia
• Blood lacks clotting
factor, most of which
are produced in the
liver.
Colorblindness Example
• Colorblindness is a
recessive disorder carried
on the X-chromosome.
• A female carrier of
colorblindness and a
normal male want to
have children. What is
the probability they will
have a child who is
colorblind?