Incomplete Dominance

DEPARTMENT OF EDUCATION
INCOMPLETE DOMINANCE

Lesson Objectives:
1. Explain incomplete dominance
pattern of inheritance
2. Illustrate by means of Punnett
square a cross involving incomplete
dominance pattern of inheritance

UNLOCKING OF TERMS
P Generation – Parent generation
F1 – First filial generation
F2 – Second filial generation
Gene - the basic unit capable of transmitting
characteristics from one generation to the
next
Allele - Alternative version of a gene

UNLOCKING OF TERMS
Dominant Allele – presence determines the
phenotype
Recessive Allele – allele whose phenotypic effect
is not observed in a heterozygote
Phenotype – the physical and physiological traits
of an organism
Genotype – genetic make up of an organism
Homozygous – containing two identical alleles
for a gene

UNLOCKING OF TERMS
Homozygous – containing two identical alleles
for a gene
Heterozygous - containing two different alleles
for a gene
Punnett Square – a diagram used in the study of
inheritance to show the predicted results of
random fertilization in genetic crosses.

Activity 1

Materials
Worksheets
Manila Paper
Pentel Pen

In Four o’clock plants, R is the allele for red color
and W is the allele for white color. The
intermediate color (pink) is controlled by RW.
• Read the given problem.
• Using a Punnett square, show the possible
outcome of a cross between
a. Two pink flowered four o’clock plants
b. Red and pink flowered four o’clock plants
Activity 1

Guide Questions:
How many types of gametes will each parent produce
in problem A? In problem B?
What is the phenotype of a heterozygous four
o’clock flower?
What are the possible phenotypes of the offspring
from the parental cross in problem A? In problem B?
What are the possible genotypes of the offspring
from the parental cross in problem A? In problem B?

Let’s talk about it …
a. Two pink flowered four o’clock plants
b. Red and pink flowered
four o’clock plants
PINKRED
PINK WHITE
REDRED
PINK PINK

1.How many types of
gametes will each
parent produce in
problem A? In
problem B?
2.What is the
phenotype of a
heterozygous four
o’clock flower?

Let’s check it …
Q1. Problem A: Two types of gametes for each
parent, since their genotypes are RW & RW
Problem B: One parent will have one type of
gamete and the other two types of gametes,
since their genotypes are RR & RW.
Q2. Pink flowers

3.What are the possible
phenotypes of the
offspring from the parental
cross in problem A? In
problem B?
4.What are the possible
genotypes of the offspring
from the parental cross in
problem A? In problem B?

Let’s check it …
Q3. Problem A: Red, Pink, White
flowers
Problem B: Red & Pink flowers
Q4. Problem A: RR, RW, WW
Problem B: RR, RW

• Incomplete Dominance
–a pattern of inheritance in which one
allele for a specific trait is not
completely dominant over the other
allele.
–results in a third phenotype,
intermediate between 2
homozygotes.

• If you are a flower farmer who supplies
to flower shops in Tagum City, how will
you use your knowledge on incomplete
dominance to increase your income?

Let’s work on it…
KNOWLEDGE
1. What is the phenotype of a heterozygous four o’clock
flower?
PROCESS/SKILL
2. What cross would produce most pink-flowered four
o’clock plants? Show a Punnett square to support your
answer?

Let’s work on it…
UNDERSTANDING
3. You are wavy-haired woman. How could you have
a greater chance of having a straight-haired child?
Explain your answer and use a Punnett square to
support it?

Let’s extend…
Using the Punnet Square, come up with the
Phenotype and Genotype in Incomplete
Dominance for the given scenarios:
1. Coat color in mice is incompletely
dominant. Yellow and white-colored mice
are homozygous, while cream-colored mice
are heterozygous. If two cream-colored
mice mate, what phenotypic ratio can we
expect of their offspring? Show the Punnett
Square.

Let’s extend…
2. In radishes, red and white are pure-
breeding colors, while hybrids are purple.
If a red radish is crossed with a white
radish, what will be the phenotype of the F2
generation (assuming the F1
generation
self-pollinates)? Show the Punnett Square.

OUTPUT/PERFORMANCE
GOAL Your goal is to create a brochure that contains tips on how to augment
floral business in the locality
ROLE You are a science student
AUDIENCE Flower growers
SITUATION You need to educate flower growers to venture on
new techniques in producing a new breed of
flowers
PRODUCT You need to come up with a flower business
brochure
STANDARD Your brochure should be organized and in logical
order, show new production techniques, creative
and must be presented to the audience.

Let’s critique…
10 8 6 4-1
Presentation content
Shows a full
understanding of
the topic.
Shows a good
understanding of
the topic
Shows a good
understanding of
parts of the topic.
Does not seem to
understand the
topic very well
Organization and
Logical Order
The brochure is
exceptionally
attractive in terms
of design, layout,
and neatness. It
is easy to
understand and
follow.
The brochure is
attractive in terms
of design, layout
and neatness. It
is easy to
understand and
follow.
The brochure is
acceptably
attractive though
it may be a bit
messy. May be
unorganized and
hard to follow.
The brochure is
distractingly
messy or very
poorly designed.
It is not attractive.
Creativity
Several of the
graphics used on
the brochure
reflect an
exceptional
degree of student
creativity in their
creation and/or
display.
One or two of the
graphics used on
the brochure
reflect student
creativity in their
creation and/or
display.
The graphics are
made by the
student, but are
based on the
designs or ideas
of others.
No graphics
made by the
student are
included

Let’s try…
Achondroplasia (dwarfism) is caused by a
dominant gene. A woman and a man both
with dwarfism marry. If homozygous
achondroplasia results in death of
embryos, summarize the genotypes and
the phenotypes of all potential live birth
offspring?

Incomplete Dominance

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