1. Punnett Square Practice
Genetics
Punnett Square Practice

2. Genetics Practice Problems
1. For each genotype below, indicate whether it is heterozygous (Ht) or homozygous (Ho)
AA Bb Cc DD
Ee ff Gg HH
Ii JJ kk LL
Mm nn oo PP

3. 2. For each of the genotypes below determine what phenotypes would be possible.
Consider: Purple flowers are dominant to white flowers (P) & Brown eyes are dominant to blue eyes (B)
PP __________ BB __________
Pp __________ Bb __________
PP __________ bb __________

4. #2 Continued
Round seeds are dominant to wrinkled seeds (R) Bobtails in cats are recessive (T).
RR __________ TT__________
Rr ___________ Tt __________
rr ___________ tt ___________

5. 3. For each phenotype below, list the genotypes (remember to use the letter of the dominant trait)
Straight hair is dominant to curly hair (S).
________ straight
________ curly
Pointed heads are dominant to round heads (H).
________ pointed
________ round

6. PUNNETT SQUARES Crosses Involving One Trait
In a certain species of animal, black fur (B) is dominant over brown fur (b). Using a Punnett square, predict the genotypes and phenotypes of the offspring whose parents are both Bb, having heterozygous black fur.
Genotypes: ___% homozygous black fur (BB)
__ % heterozygous black fur (Bb)
___% homozygous brown fur (bb)
Phenotypes: ___% black fur
___ % brown fur

7. Now do the same when:
One parent is homozygous black and the other is homozygous brown.
Genotypes: ___% homozygous black fur (BB)
___ heterozygous black fur (Bb)
___% homozygous brown fur (bb)
Phenotypes ___% black fur
___% brown fur

8. Repeat this process again when
One parent is heterozygous black and the other is homozygous brown.
Genotypes: ___% homozygous black fur (BB)
___ heterozygous black fur (Bb)
___% homozygous brown fur (bb)
Phenotypes ___% black fur
___% brown fur

9. Set up a Punnet square for each of the following crosses.
Round seeds are dominant to wrinkled seeds
(Rf x rr). What percent of these offspring will be round?
RR x rr What percent of these offspring will be round?
RR x Rr What percent of these offspring will be round?
Rr x Rr What percent of these offspring will be round?

10. 5. A (tall) TT plant is crossed with a (short plant) tt
5. A (tall) TT plant is crossed with a (short plant) tt. What percent of the offspring will be tall? 6. A Tt plant is crossed with a Tt plant. What percent of the offspring will be short? 7. A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR). What percent of the offspring will be homozygous (RR)?

11. 8. A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant. What are the genotypes of the parents? _____________ x ______________ What percent of the offspring will also be homozygous? 9. In pea plants purple flowers are dominant to white flowers. If two white flowered plants are cross, What percentage of their offspring will be white flowered?

12. 10. A white flowered plant is crossed with a plant that is heterozygous for the trait.
What percentage of the offspring will have purple flowers?
11. Two plants, both heterozygous for the gene that controls flower color are crossed.
What percentage of their offspring will have purple flowers?
What percentage will have white flowers?

13. 12. In guinea pigs, the alleles for short hair are dominant.
What genotype would a heterozygous short haired guinea pig have?
What genotype would a purebred, short haired guinea pig have?
What genotype would a long haired guinea pig have?
13. Show the cross for a pure breed, short haired guinea pig and a long haired guinea pig.
What percentage of the offspring will have short hair?

14. 14. Show, the cross for two heterozygous guinea pigs
14. Show, the cross for two heterozygous guinea pigs. What percentage of the offspring will have short hair? What percentage of the offspring will have long hair? 15. Two short haired guinea pigs are mated several times. Out of 100 offspring, 25 of them have long hair. What are the probable genotypes of the parents? _________ x Show the cross to prove it!

15. Dragon Genetics Remember:
UPPER CASE LETTERS REPRESENT DOMINANT ALLELES
AND
Lower case letters represent recessive alleles

16. Dragon Genetics, cont.
N = LONG NECK E = RED EYES N = short neck e = white eyes H = HORN PRESENT F = FIRE BREATHING h = horn absent f = not fire breathing G = GREEN BODY L = LONG TAIL G = grey body l = short tail S = SPIKES ON TAIL R = RED WINGS S = no spikes on tail r = yellow wings

17. T = THREE TOES W = YELLLOW BELLY t = four toes w = white belly B = BLACK TAIL SPIKES K = FRECKLES b= red tail spikes k = no freckles X = X = NO EAR FRILLS Y = EAR FRILLS XX = FEMALE YY = MALE

18. Dragon Genetics Questions Using the Dragon Code, answer the following questions.
What letters are used to represent wing color?
What letters are used to represent neck length?
The letter “Y” is used as a symbol to represent _____________________.
The letter “e” is used to represent ________.

19. REMEMBER:
An upper case, or lower case letter, is used to represent a dominant trait.
A lower case, or small letter, is used to represent a recessive trait.
Dominant traits completely mask recessive traits
Refer to the Dragon key to answer the following questions.

20. 5. List 6 dominant traits shown in the key. 6
5. List 6 dominant traits shown in the key. 6. List 6 recessive traits shown in the key. 7. Fill in the blanks
Traits
Genotype
Phenotype
Neck Size
NN or Nn
Short neck
Spikes on Tail
No spikes
Eye Color EE
Horn (present or absent) Hh
Fire Breathing
______ or ______
Breaths fire
Belly Color
WW or Ww
Color of Spikes
Red
Tail Length
Long

21. 10. Cross a male dragon with a short neck with a female dragon that is purebred for a long neck. Show percentages of offspring. 11. Cross a hybrid fire breathing dragon with a homozygous recessive non-fire breathing dragon. Show percentages of offspring.

22. Dihybrid Cross
Example: cross between hair and eye color heterozygous pea seeds.
B = Black
b = blonde
E = Brown
e = blue
BbEe x BbEe
BE Be bE be x BE Be bE be
possible gametes produced

23. Punnett Squares - Dihybrid Crosses Involve the Cross of Two Traits
In a dihybrid cross, when two traits are considered, the number of possible combination of the offspring increases.
Suppose that Black hair (B) is dominant over blonde hair (b)
and
Brown eyes (E) are dominant over blue eyes (e).
Whqt percent of offspring could be expected to have blonde hair and blue eyes if;
1. The father has black- hair (heterozygous) and brown eyes (heterozygous) and the mother has blonde hair and blue eyes.
Genotype of father— BbEe
Genotype of mother— bbee
Copy the following Punhett square, then, fill in the boxes.

24. Dihybrid Cross

25. Dihybrid Cross _______/______: __ _______/______: __
_______/______: __
_______/______: __
_______/_______: __
_________ phenotypic ratio