NAME: ____________________________
GENETICS PACKET
***DO NOT LOSE ME!***
PERIOD: ____
COMPLETE DOMINANCE
1.
Describe the genotypes given.
a. DD Homozygous dominant
d. ss _____________________
b. Dd Heterozygous
e. Yy ______________________
c. dd ____________________
f. WW _____________________
2. In humans, brown eyes (B) is dominant over blue eyes (b). What are the phenotypes of the following
genotypes?
a. BB _____________________
b. Bb _____________________
c. bb ______________________
***ON A SEPARATE SHEET OF PAPER THAT WILL BE TURNED IN, DO THE FOLLOWING PROBLEMS:
Title the page: COMPLETE DOMINANCE
Each genetic cross must show the parent alleles, the full Punnett square, and complete genotypic and phenotypic ratios.
1.
2.
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4.
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7.
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10.
What does “complete dominance” mean?
A heterozygous tall pea plant is crossed with a homozygous short pea plant. T = Tall and t = short.
A white mouse is mated with a black mouse. Both were from a pure strain (homozygous). B = black, b = white.
Any time a homozygous dominant and homozygous recessive are crossed, the offspring can be referred to as the
F1 generation. Cross two mice from the F1 generation of problem #3.
Black eyes in mice is dominant over red. A black-eyed homozygous male mates with a black-eyed heterozygous
female. Use B = black, b = red.
A red-eyed male mates with a homozygous black-eyed female.
Show the cross between the F1 generation of problem #6.
Blue flowers is dominant over white. A plant with white flowers is crossed with a plant with blue flowers. The
blue flowered plant had a parent whose flowers were white. Use B = blue, b = white.
Two heterozygous blue-flowered plants are crossed.
Two homozygous white-flowered plants are crossed.
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Title the page: More Punnett square practice
Use a Punnett Square, genotypic and phenotypic ratios to show the possible offspring from the crosses given and
answer the questions.
IN PEAS: R = round
r=wrinkled
T= tall
t = short
Y = yellow peas
P = purple flowers
y = green peas
p = white flowers
1. Make a cross between a PURE YELLOW SEED parent and a PURE GREEN SEED parent.
 What is the probability an offspring will show the DOMINANT TRAIT (YELLOW SEEDS)? _________
 What is the probability an offspring will show the RECESSIVE TRAIT (GREEN SEEDS)? ________
2. Make a cross between a HOMOZYGOUS PURPLE FLOWERED plant and a HOMOZYGOUS WHITE FLOWERED plant.
 What is the probability an offspring will show the DOMINANT TRAIT (PURPLE FLOWERS)? ___________
 What is the probability an offspring will show the RECESSIVE TRAIT (WHITE FLOWERS)? _____________
3. SEE A PATTERN FOR HOMOZYGOUS MONOHYBRID CROSSES:
If you cross plants that are PURE DOMINANT for a trait with plants that are PURE RECESSIVE for that trait, ________ %
of the offspring will show the DOMINANT trait and the ___________________ trait will not show at all.
USE THE PATTERN ABOVE TO MAKE PREDICTION ABOUT A CROSS
4. If you cross a HOMOZYGOUS ROUND SEED plant with a PURE WRINKLED SEED plant
100% will look __________________
0% will look ____________________
The offspring will have a 100% probability of having the ______ genotype.
MAKE SOME HETEROZYGOUS MONOHYBRID CROSSES
5. A black coat (B) is DOMINANT in guinea pigs. A brown coat (b) is RECESSIVE.
 What is the genotype of a HOMOZYGOUS BLACK guinea pig? = _______
 What is the GENOTYPE of a HETEROZYGOUS BLACK guinea pig? =_________
 What is the GENOTYPE of a brown guinea pig? =__________
6. Make a cross between TWO HETEROZYGOUS BLACK guinea pigs.





What is the probability that a baby will be black? _________
What is the probability that a baby will be brown? _________
What is the probability the baby will be a HYBRID? ________
What is the probability the baby will be HOMOZYGOUS DOMINANT? _________
What is the probability the baby will be HOMOZYGOUS RECESSIVE? ___________
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7. Purple fur (P) is DOMINANT in monsters. Yellow fur (p) is RECESSIVE.
 What is the genotype of a PURE PURPLE monster? = ________
 What is the GENOTYPE of a HETEROZYGOUS purple monster? _________
 What is the GENOTYPE of a YELLOW monster? = ________
8. Make a cross between TWO HETEROZYGOUS PURPLE MONSTERS.





What is the probability that a baby will be purple? __________
What is the probability that a baby will be yellow? __________
What is the probability the baby will be a heterozygous? __________
What is the probability the baby will be HOMOZYGOUS DOMINANT? _________
What is the probability the baby will be HOMOZYGOUS RECESSIVE? ___________
SEE A PATTERN FOR HETEROZYGOUS MONOHYBRID CROSSES:
9. If you cross 2 parent plants that are BOTH HETEROZYGOUS for a trait the offspring will show a ____ : ____ phenotypic
ratio.
________ % of the offspring will show the DOMINANT trait and
________ % of the offspring will show the RECESSIVE trait.
USE DOMINANT OR RECESSIVE TO FILL IN THE BLANKS BELOW:
¼ of the offspring will have two __________________ alleles,
½ will be hybrids with one _______________ and one _______________ allele, and
¼ will have two _________________ alleles.
USE THE PATTERN ABOVE TO MAKE PREDICTION ABOUT A CROSS
10. If you cross two HETEROZYGOUS ROUND SEED plants
75% will look __________________
25% will look __________________
The probability is: ¼ will have the genotype ______ ½ will have the genotype _____ ¼ will have the
genotype _____
BACK CROSS / TEST CROSS
11. When an organism has the dominant phenotype, you cannot tell its genotype by looking at it. For example, if B =
black and b = brown, a black guinea pig may be BB or Bb. How can we find out?
Below, show the cross you would make with your B__ guinea pig that would give us the most information about the
other allele. In other words, what can you cross the pig with to determine if it is BB or Bb?
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INCOMPLETE DOMINANCE
Incomplete dominance is a genetic phenomenon in which an individual displays a trait that is intermediate between the
two parents. Another way to describe it is that there is a “blending” of the traits. In the problems we have done so far,
a homozygous dominant individual has the same phenotype as a heterozygous individual. That is, a BB black mouse
looks just like a Bb black mouse. There are some genes for which this is not true. For example, in Japanese four-o’clocks
(a type of flower), plants with two red alleles (RR) have red flowers. Plants with two white (rr) alleles have white
flowers. However, plants with one red allele and one white allele (Rr) are pink!
Perform the following crosses in the same way you would for complete dominance. You may continue to use one capital
and one lower case letter, or you may use two different letters. Just remember that a heterozygote now looks different
(and will be recorded differently in the phenotype) from a homozygous dominant individual.
** ON A SEPARATE SHEET OF PAPER THAT WILL BE TURNED IN, DO THE FOLLOWING PROBLEMS:
Title the page: INCOMPLETE DOMINANCE CROSSES
Each genetic cross must show the parent alleles, the full punnett square, and complete genotypic and
phenotypic ratios.
1. Predict the outcomes of the following crosses of Japanese four-o’clocks:
a. a red plant and a white plant
b. a white plant and a pink plant
c. a red plant and a pink plant
d. two pink plants
2. In some cats the gene for tail length shows incomplete dominance. Cats with long tails and those with
no tails are homozygous for the respective alleles. Cats with one long tail allele and one no tail allele
have short tails. First pick the letters you will use for each trait, then predict the outcomes of crosses
between:
a. a long tail cat and a cat with no tail
b. a long tail cat and a short tail cat
c. two short tail cats
3. In guinea pigs, brown fur (B) is dominant to white (b). The heterozygous condition results in creamcolored fur. Cross a brown guinea pig with a cream-colored guinea pig. Provide the genotypic and
phenotypic ratios.
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CODOMINANCE
Codominance is a genetic phenomenon in which a heterozygote shows BOTH traits. For example, a black
mouse crossed with a white mouse will look black and white. Crosses for these traits are done the same as
crosses for complete or incomplete dominance.
*Add these problems to your incomplete dominance page but label a new section “Codominance”.
1. In “pufferbelly pigs” spot color is inherited through codominance. Some pufferbelly pigs have pink skin with green
spots (G), while others have pink skin with yellow spots (g). Some really special pufferbelly pigs have pink skin with green
and yellow spots.

List the three possible genotypes and phenotypes for pufferbelly pig spot color below (set up a key):

Show the results (genotypes, phenotypes and their percentages) of a cross between two pufferbelly pigs
heterozygous for the spot color gene.
Once upon a time…
2. There were dragons that wanted to have baby dragons. The female had hot flame breath (HH) and the male had cool
flame breath (hh). The warm breath gene is (Hh).

List the three possible genotypes and phenotypes for dragon breath below (set up a key):

Complete a Punnett square for the cross of the male and female in the original question. What are the
genotypes and phenotypes that could result from this cross?
3. Scale color in dragons is controlled by a gene. The blue spot color gene is B and the yellow spot color gene is b. Some
dragons have yellow and blue spots.

List the three possible genotypes and phenotypes for dragon spot color below (set up a key):

Complete a Punnett square for a cross between dragons – both with blue and yellow spots. What are the
genotypes and phenotypes that could result from this cross?
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Practice: Codominance and Incomplete Dominance
1. Practice setting up keys for the phenotypes listed in each set. Remember that the "medium" trait must always be
heterozygous.
a) Birds can be blue (B), white (b), or white with blue-tipped feathers.
b) Flowers can be white (W), pink, or red (w).
c) A Hoo can have curly hair (H), spiked hair (h), or a mix of both curly and spiked.
d) A Sneech can be tall (T), medium, or short (t).
e) A Bleexo can be spotted, black (B), or white (b).
2. Now, can you figure out in the above (1a-1e), which of the letters (a, b, c, d, and e) represent codominant traits and
which are incomplete?
Codominant are letters: _____________
Incompletely Dominant are letters:________________
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3. In Smileys, eye shape can be starred (E), circular (e), or a circle with a star. Write the genotypes for the pictured
phenotypes on the lines below each Smiley.
________
________
________
4. Show the cross between a star-eyed and a circle eyed.
What are the phenotype ratios of the offspring? ____________
What are the genotype ratios? __________
5. Show the cross between a circle-star eyed, and a circle eyed.
How many of the offspring are circle-eyed? ____________
How many of the offspring are circle-star eyed? ____________
6. Show the cross between two circle-star eyed.
How many of the offspring are circle-eyed? ____________
How many of the offspring are circle-star eyed? ____________
How many are star eyed? ____________
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DIHYBRID CROSSES AND BEYOND
For all of the crosses we’ve done so far, we’ve only considered one trait at a time. Is a pea plant tall or short?
Does a pea plant have round seeds or wrinkled seeds? Well, what if we want to know the chances of two
traits showing up in the offspring? We must consider a dihybrid cross for this.
How To Solve a Dihybrid Cross
1. Read the problem and find the two separate traits.
In Springfield, red hair (H) is dominant to blue hair (h) and having four fingers (F) on your hand is dominant to
having five fingers (f). If Side Show Bob and Mrs. Van Houten get married and decide to have a little brother for
Millhouse, what is the chance that the newborn will have red hair and five fingers if Side Show is heterozygous for
red hair and heterozygous for four fingers and Mrs. Van Houten has blue hair and is homozygous for four fingers?
2. Find the two parents and write down their genotypes.
Dad’s alleles = ______________________________
Mom’s alleles = ______________________________
3. Read the question and see what you have to look for. Do they want you to find a ratio, percent, fraction, or do
they want you to list all possibilities?
4. Once you have found all the information, you can start to set up the problem by finding the gametes for each
parent by using FOIL.
•
Here is an example of how to use FOIL:
• (a + b) * (c + d)
• First = (a + b) * (c + d) = ac
• Outside = (a + b) * (c + d) = ad
• Inside = (a + b) * (c + d) = bc
• Last = (a + b) * (c + d) = bd
• So our pairs are: ac, ad, bc, bd
•
Here is another example
a
b
c
ac
bc
d
ad
bd
Dad’s gametes = ________, ________,________,________
Mom’s gametes = ________,________,________,________
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5. Once you have the gametes, you have to line them up in a punnett square. Put the gametes of one parent across
the top of the square and the other down the side of the square
6. Now you have to do the actual cross. Fill in the rest of the boxes!
7. Find the genotypic ratio.
Genotypic ratio:
8. Find the phenotypic ratio.
Phenotypic ratio:
9. Now, don’t forget to answer the question!
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***In the space below, do the following problems.
Trait
Body color
Dominant Phenotype
(B) purple
Recessive Phenotype
(b) red
Tentacle suckers (A) present
(a) absent
Size of Lips
(L) thin
(l) thick
Diet / Type of
Teeth
(D) pointed = carnivore
(d) blunt = herbivore
# of Tentacles
(T) 8
(t) 4
1. A carnivorous male with 4 tentacles mates with an 8-tentacled female who also eats meat. The male is heterozygous
for the diet trait. The female's tentacle genotype is hybrid but her diet genotype is pure. What is the chance this couple
will produce a carnivorous baby with 8 tentacles?
2. A red male with thin lips mates with a thin-lipped purple female. The female is heterozygous for the body color
trait. As for the lips, both aliens are heterozygotes. What is the chance that their baby will be red and have thick lips?
3. Rock, a thin-lipped male that lacks tentacle suckers, is having a baby with Amber, a thick-lipped female who also lacks
tentacle suckers. Rock fell in love with Amber because of her thick lips. Rock's mother had thick lips and it is common
for this alien species to select a mate with features similar to the maternal parent. What is the chance that Amber will
give birth to a thin-lipped baby that has tentacle suckers?
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Dihybrid Cross Poster Project
Objective:
This project involves creativity as well as genetics. You will choose any “organism” and two traits to cross. You will
diagram the cross on a poster. In each square of the diagram, you will write the genotype of the offspring and draw the
phenotype.
Key:
1. Choose a thing to cross. It does not have to be a living thing, just something fun to cross and something you can
draw without too much trouble.
Example: Frogs
I will cross: ___________________________________________
2. Choose two traits you will examine.
Example: color and tongue length
I will examine: _________________________ and _______________________
3. Define the alleles for your traits. You will need to take into account how many alleles there will be for each trait
and what pattern of inheritance they will follow (complete, incomplete, or codominance). Use your notes to
come up with creative, challenging allele possibilities.
Example:
Color (GG = green; Gg = green; gg = blue)
Tongue length (LL = long; Ll = long; ll = short)
My alleles will be:
TRAIT: ________________________
Alleles: ______ = ______________
______ = ______________
______ = ______________
TRAIT: ________________________
Alleles: ______ =_______________
______ = _______________
______ = _______________
4. Now, decide the phenotypes and genotypes of the parents. Remember, the more varied your parent genotype
is, the more interesting phenotypes you will get in the offspring. More variety = better grade!
Example: I will cross a green, long tongued male with a blue, long tongued female
Phenotype of my parents: _________________________ x _______________
Example: I will cross GgLl x ggLL
Genotype of my parents: _______________________ x __________________
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5. FOIL their genotypes to determine their possible gametes.
Dad’s gametes: __________________________________
Mom’s gametes: _________________________________
6. Complete the cross.
7. Determine the genotypic ratio of your cross:
8. Determine the phenotypic ratio of your cross:
9. Now you are ready to make your poster! Be sure to include:
 name/description of the “organism” (living, non-living, fictional)
 description/key of the TWO traits and the alleles/versions of each (you will receive more points for
using co-dominance or incomplete dominance – but be careful, it’s harder!)
 parent’s genotypes and a PICTURE of their phenotypes (you will receive more points for using
heterozygous genotypes)
 list of parents gametes (results of FOIL)
 dihybrid punnett square (each box should include the offspring’s genotype AND a picture of its
phenotype)
 list of possible genotypes and phenotypes with fractions
** Pictures can be drawn or computer generated.
** Be neat. Include all required information.
** Remember – you determine what the traits, alleles, and parents will be.
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Dihybrid Poster Scoring Rubric
Your score:
________ / 3 points Both Traits are complete dominance
+2 pts. One trait is Incomplete or Codominant
+4 pts. Both traits are Incomplete or Codominant
________ / 2 points Parents genotype – homozygous
+2 pts. some traits heterozygous
+4 pts. all traits heterozygous
________ / 2 points Parents phenotypes
________ / 4 points Correct gametes/Allele combinations outside of punnett square
________ / 4 points Correct genotypes of possible offspring inside punnett square
________ / 4 points Correct phenotypes of possible offspring inside the punnett square
________ / 4 points Correct genotypic ratio of offspring
________ / 4 points Correct phenotypic ratio of offspring
________ / 3 points Appearance of poster – correct paper, colorful, clear drawings of traits, neat
________ / 30 points total score
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REVIEW
4 types of basic genetics problems
Complete Dominance
Incomplete
Dominance
Co-dominance
Dihybrid Cross
Characteristics:
Characteristics:
Characteristics:
Characteristics:
Example:
Example:
Example:
Example:
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