Question

1. one of spongebobs cousins, spongebillybob, recently met a cute squarepants gal, spongegerdy, at a local dance and fell in love. use your knowledge of genetics to answer the questions below.

(a) if spongegerdys father is a heterozygous squarepants and her mother is a roundpants, what is her genotype? complete the punnett square to show the possible genotypes that would result to help you determine gerdys genotype.
what is gerdys genotype? ______
(b) spongebillybob is heterozygous for his squarepants shape. what is his genotype? ______
(c) complete the punnett square to show the possibilities that would result if billy bob & gerdy had children.
(d) list the possible genotypes and phenotypes for the kids.
(e) what is the probability of kids with squarepants? ______%
(f) what is the probability of kids with roundpants? ______%
t. trimpe 2003 http://sciencespot.net/

Explanation:

Step1: Define allele notation

Let $S$ = squarepants (dominant), $s$ = roundpants (recessive)

Step2: Find Gerdy's genotype

Father: $Ss$ (heterozygous squarepants), Mother: $ss$ (roundpants). Punnett square for parents:

$$\begin{array}{|c|c|} \hline S & s \\ \hline s & Ss \\ \hline s & ss \\ \hline \end{array}$$

Gerdy has squarepants, so her genotype is $Ss$.

Step3: Define BillyBob's genotype

Heterozygous for squarepants = $Ss$

Step4: Complete offspring Punnett square

Cross $Ss$ (Gerdy) × $Ss$ (BillyBob):

$$\begin{array}{|c|c|c|} \hline & S & s \\ \hline S & SS & Ss \\ \hline s & Ss & ss \\ \hline \end{array}$$

Step5: List offspring genotypes/phenotypes

Genotypes: $SS$, $Ss$, $ss$
Phenotypes: Squarepants ($SS$, $Ss$), Roundpants ($ss$)

Step6: Calculate squarepants probability

3 out of 4 offspring have squarepants: $\frac{3}{4} \times 100 = 75\%$

Step7: Calculate roundpants probability

1 out of 4 offspring have roundpants: $\frac{1}{4} \times 100 = 25\%$

Answer:

(a) Gerdy's genotype: $Ss$
Punnett square for Gerdy's parents:

$$\begin{array}{|c|c|} \hline S & s \\ \hline s & Ss \\ \hline s & ss \\ \hline \end{array}$$

(b) SpongeBillyBob's genotype: $Ss$
(c) Punnett square for BillyBob & Gerdy:

$$\begin{array}{|c|c|c|} \hline & S & s \\ \hline S & SS & Ss \\ \hline s & Ss & ss \\ \hline \end{array}$$

(d) Possible genotypes: $SS$, $Ss$, $ss$
Possible phenotypes: Squarepants, Roundpants
(e) Probability of squarepants kids: 75%
(f) Probability of roundpants kids: 25%