Bikini Bottom – Dihybrid Practice
Use the chart to identify the genotypes of the
following traits:
Trait
Dominant Gene
Recessive Gene
Body Shape
Squarepants (S)
Roundpants (s)
Body Color
Yellow (Y)
Blue (y)
Eye Shape
Round (R)
Oval (r)
Nose Style
Long (L)
Stubby (l)
1. Heterozygous round eyes, blue body ________
2. Hybrid eye shape, purebred roundpants ________
3. Purebred roundpants, heterozygous long nose ________
SpongeBob’s aunt, who is a roundpants, has a cute stubby nose. She has finally found the sponge of her dreams and is ready to settle down. Her fiancé always comments on how adorable her nose is (he says it reminds him of his mother’s – aww, how sweet!). They wonder what the chances are of that trait being passed on. Her fiancé is a purebred squarepants and has a purebred long nose.
4. Identify the genotypes of the aunt and her fiancé.
Aunt – Roundpants, Stubby Nose = ________
Fiancé – Purebred Squarepants, Long Nose = ________
5. What are the possible gamete combinations for each person?
Aunt – ________
Fiancé – ________
6. What are the possible genotypes for their children? ______________________________________
7. What are the genotypes of SpongeBob, who is heterozygous for his yellow body color and his squarepants, and his wife SpongeSusie, who is blue and has roundpants?
SpongeBob = ________
SpongeSusie = ________
8. What are the possible gamete combinations for each person?
SpongeBob = ________________
SpongeSusie = ________
9. Complete the Punnett square based on the information provided in #7-8 and then answer the questions.
What is the chance of a blue baby? ________
What is the chance of a squarepants? ________
What is the chance of a blue squarepants? ________
What is the chance of a purebred recessive for both traits? ________
10. In starfish, pink body color (P) is dominant to orange (p), and thick eyebrows (T) are dominant over thin (t) ones. Patrick, who is heterozygous for body color but purebred for thick eyebrows, has met Patti, who is recessive for both traits.
What is Patti’s phenotype? _______________________________
Is it possible for the new couple to have offspring that resemble their mother? Explain.
________________________________________________________________________
________________________________________________________________________
11. Before Patrick commits to this relationship, he would like to guarantee that his offspring would have his thick eyebrows. (He thinks they make him smarter!) You need to provide evidence for or against the marriage. This question regards eyebrows ONLY.
_________________________________________________________________
________________________________________________________________
12. While Squidward’s family boasts about being a purebred line for dominant
blue skin color, they are also purebred for a less distinguished trait: the recessive trait of baldness. He would like to ensure that his offspring have hair AND with his blue skin color. What traits should he look for in a bride?
Squidward Traits:
Skin Color
Blue = B, Green = b
Hair
Hair = H, Bald = h
Must she have hair? Explain. ____________________________________________________
Must she be blue? Explain. ____________________________________________________
13. Squidward has found a potential bride prospect with the green squid Octavia. While Octavia has hair, her father does not. Determine the chances of their child being blue and having hair.
Squidward = ________
Octavia = ___________
14. Use the genotypes in #13 to complete the Punnett square below and then answer the questions.
For which traits, if any, is it possible for their offspring to be purebred?____________
What is the probability of their children being heterozygous for both traits? ________
1. Heterozygous round eyes, blue body: RrYy
2. Hybrid eye shape, purebred roundpants: RRSs
3. Purebred roundpants, heterozygous long nose: RrLL
4. Aunt - Roundpants, Stubby Nose: Rrll
Fiancé - Purebred Squarepants, Long Nose: SsLL
5. Aunt - RL, rl
Fiancé - SL, LL
6. Possible genotypes for their children: Squarepants with either round or oval eyes, and either long or stubby nose.
7. SpongeBob - SsYy
SpongeSusie - ssyy
8. SpongeBob - SY, Sy, sY, sy
SpongeSusie - sy
9. Punnett square:
SY Sy sY sy
----------------------------------------
sy | SYsy | Sssy | SYY | Syy
----------------------------------------
sy | SYsy | Sssy | SYY | Syy
What is the chance of a blue baby? 75%
What is the chance of a squarepants? 50%
What is the chance of a blue squarepants? 25%
What is the chance of a purebred recessive for both traits? 0%
10. Patti's phenotype is orange body color and thin eyebrows.
It is not possible for the new couple to have offspring that resemble their mother because Patrick does not carry the recessive traits for body color or eyebrow thickness.
11. Patrick can guarantee that his offspring will have thick eyebrows because he is purebred for that trait.
12. Squidward should look for a bride who is heterozygous for both traits (BbHh).
Must she have hair? Yes, because Squidward is purebred for hair.
Must she be blue? Yes, because Squidward is purebred for blue skin color.
13. Squidward = BbHh
Octavia = bbHh
14. Punnett square:
Bb bb
---------------------
Hh | BbHh | bbHh
---------------------
For which traits, if any, is it possible for their offspring to be purebred? Hair trait.
What is the probability of their children being heterozygous for both traits? 50%
1. Heterozygous round eyes, blue body: Genotype: RrYy
2. Hybrid eye shape, purebred roundpants: Genotype: Rr
3. Purebred roundpants, heterozygous long nose: Genotype: rrLl
4. Aunt – Roundpants, Stubby Nose: Genotype: Rrll
Fiancé – Purebred Squarepants, Long Nose: Genotype: SSLL
5. Aunt possible gamete combinations: RL, rL
Fiancé possible gamete combinations: SL
6. Possible genotypes for their children are:
- Roundpants, Stubby Nose: Rrll
- Squarepants, Stubby Nose: SSll
- Roundpants, Long Nose: RrLl
- Squarepants, Long Nose: SsLl
7. SpongeBob = YySS
SpongeSusie = yyRr
8. SpongeBob possible gamete combinations: YS, yS
SpongeSusie possible gamete combinations: yR, yr
9. Punnett square (assuming Y, S, R, and L are all on separate chromosomes):
YS yS
yR YYSs yYSs
yr YYSs yySs
Chance of a blue baby: 2/4 = 50%
Chance of a squarepants: 2/4 = 50%
Chance of a blue squarepants: 1/4 = 25%
Chance of a purebred recessive for both traits: 1/4 = 25%
10. Patti's phenotype: Homozygous recessive for body color (pp) and thin eyebrows (tt).
It is not possible for the new couple to have offspring that resemble their mother because the father is heterozygous for body color (Pp) and homozygous dominant for thick eyebrows (TT), so all their offspring would have at least one dominant trait (either pink body color or thick eyebrows).
11. Regarding eyebrows only, based on Patrick being heterozygous for thick eyebrows (Tt) and Patti being homozygous recessive for thin eyebrows (tt), there is a 50% chance that their offspring will have thick eyebrows (Tt).
12. Squidward should look for a bride with the following traits:
Skin Color: Blue (BB or Bb)
Hair: Hair (HH or Hh)
She must have hair to ensure that their offspring will have hair, as the bald trait is recessive (hh). She should be blue to ensure that their offspring will have blue skin color, as the green trait is recessive (bb).
13. Squidward = Bbhh
Octavia = bbHh
14. Punnett Square:
Bb Bb
bbHh BbHh BbHh
For which traits, if any, is it possible for their offspring to be purebred?
- For hair, it is possible for their offspring to be purebred (HH or hh).
- For skin color, it is not possible for their offspring to be purebred as both parents are heterozygous (Bb).
The probability of their children being heterozygous for both traits is 2/4 = 50%.
To identify the genotypes of the traits mentioned, we can use the chart provided. Let's go through each question step by step:
1. Heterozygous round eyes, blue body
- From the chart, round eyes are represented by the genotype Rr, and blue body is represented by the genotype yy.
- So, the answer is Rryy.
2. Hybrid eye shape, purebred roundpants
- Here, hybrid eye shape means that the genotype can be either RR or Rr (since round is dominant).
- Purebred roundpants means that the genotype is rr.
- So, the answer is either RRrr or Rrrr.
3. Purebred roundpants, heterozygous long nose
- Purebred roundpants means the genotype is rr.
- Heterozygous long nose means the genotype can be either Ll or LL.
- So, the answer is rrLl or rrLL.
Now, let's move on to question 4:
4. Genotypes of the aunt and her fiancé
- The aunt is a roundpants and has a stubby nose.
- So, her genotype is rrll (roundpants and stubby nose).
- The fiancé is a purebred squarepants with a long nose.
- So, his genotype is SSLL (squarepants and long nose).
5. Possible gamete combinations for each person
- For the aunt (rrll), the possible gametes are rl.
- For the fiancé (SSLL), the possible gametes are SL.
Now, let's move on to question 6:
6. Possible genotypes for their children
- When gametes combine, we can use a Punnett square to determine the possible genotypes.
- Cross rl with SL, and we get 4 possible genotypes: rLSL, rLSl, rLsL, rLsl.
Moving on to question 7 and 8:
7. Genotypes of SpongeBob and SpongeSusie
- SpongeBob is heterozygous for his yellow body color, which means his genotype is Yy. He is also squarepants, so his genotype is SS.
- So, SpongeBob's genotype is SSYy.
- SpongeSusie is blue and has roundpants, so her genotype is ssrr.
8. Possible gamete combinations for each person
- For SpongeBob (SSYy), the possible gametes are SY and Sy.
- For SpongeSusie (ssrr), the possible gametes are sr.
Now, let's move on to question 9, which involves completing a Punnett square:
9. Chances based on the Punnett square
- Fill in the Punnett square with the gametes.
- The chances of having a blue baby would be shown by the number of blue squares within the Punnett square.
- The chances of having a squarepants would be shown by the number of squares with "S" within the Punnett square.
- The chances of having a blue squarepants would be shown by the number of squares with "S" and "y" within the Punnett square.
- The chances of having a purebred recessive for both traits (rryy) would be shown by the number of squares with "rr" and "yy" within the Punnett square.
Moving on to question 10:
10. Patti's phenotype and likelihood of resembling their mother
- Patti is recessive for both traits, which means her genotype is pp and tt (orange body color and thin eyebrows).
- Her phenotype would be orange with thin eyebrows.
- It is possible for the new couple to have offspring that resemble their mother if the father (Patrick) passes on the recessive alleles for both traits.
Now, let's move on to question 11:
11. Providing evidence for or against the marriage solely based on eyebrows
- Patrick wants to guarantee that his offspring will have thick eyebrows.
- Since he is heterozygous for eyebrows (Tt), there is a 50% chance that he will pass on the dominant allele (T) for thick eyebrows to his offspring.
- However, without knowing Patti's genotype for eyebrows, we cannot guarantee that the offspring will have thick eyebrows. We would need more information about Patti's genotype for eyebrows to provide a definitive answer.
Moving on to question 12:
12. Traits Squidward should look for in a bride
- Squidward wants his offspring to have both hair and blue skin color.
- To ensure this, his bride should have the genotype BbHh at the very least.
- Hair is dominant (H), so if the bride has "h" (bald) in her genotype, it will not affect the offspring's hair.
- Blue skin color is dominant (B), so if the bride has "b" (green) in her genotype, it will not affect the offspring's skin color.
Now, let's move on to question 13:
13. Chances of their child being blue and having hair
- Squidward's genotype is BBhh (purebred blue skin color and hair).
- Octavia's genotype is Bbgg (blue skin color and hair).
- Cross BBhh with Bbgg in a Punnett square to determine the chances of their child being blue and having hair.
Moving on to question 14:
14. Completing the Punnett square and answering the questions
- Fill in the Punnett square with the gametes Bg and Bg.
- The Punnett square will then show the possible genotypes.
- To determine if any offspring can be purebred for either trait, look for squares with only "B" or "H."
- The probability of their children being heterozygous for both traits (BbHh) can also be determined from the Punnett square.
I hope this helps you navigate through the Bikini Bottom dihybrid practice questions! If you have any specific questions or need further assistance, feel free to ask.