Worksheet with genetics problems involving Punnett squares for dominant and recessive traits.
Punnett square practice problems worksheet for simple dominant and recessive traits in genetics.
JPG
495×640
63 KB
Free · Personal Use
Quality Assured by Worksheets Library Team
Reviewed for educational accuracy and age-appropriateness
ID: #1071657
⭐
Show Answer Key & Explanations
Step-by-step solution for: Punnett Square Practice Problems
▼
Show Answer Key & Explanations
Step-by-step solution for: Punnett Square Practice Problems
Here are the solutions to the Punnett Square practice problems, broken down step-by-step.
1) Percentage of offspring with short whiskers (Heterozygous x Homozygous Dominant)
* Parents: One is homozygous dominant ($WW$) and the other is heterozygous ($Ww$).
* Cross: $WW \times Ww$
* Offspring Genotypes: All offspring will receive a big $W$ from the first parent. They will receive either a big $W$ or little $w$ from the second. This results in 50% $WW$ and 50% $Ww$.
* Phenotypes: Since $W$ (long whiskers) is dominant, both $WW$ and $Ww$ result in long whiskers. There are no offspring with the genotype $ww$ (short whiskers).
* Answer: 0%
2) Percentage of offspring with short whiskers (Pure Long x Short)
* Parents: Pure long-whiskered ($WW$) crossed with short-whiskered ($ww$).
* Cross: $WW \times ww$
* Offspring Genotypes: Every single offspring gets a $W$ from one parent and a $w$ from the other. Result: 100% $Ww$.
* Phenotypes: Because they all have the dominant $W$, they all have long whiskers. None have short whiskers.
* Answer: 0%
3) & 4) Purple People Eaters (Hybrid x No Horns)
* Alleles: Let's use $H$ for horns (dominant) and $h$ for no horns (recessive).
* Parents: Hybrid ($Hh$) $\times$ No horns ($hh$).
* Punnett Square Results:
* Top row ($H$, $h$) vs Side column ($h$, $h$).
* Box 1: $Hh$
* Box 2: $hh$
* Box 3: $Hh$
* Box 4: $hh$
* Summary of Genotypes: 50% $Hh$, 50% $hh$.
* Summary of Phenotypes: 50% Have horns, 50% Do not have horns.
5) Genotypes of Green-leafed Fuzzywhatsit Parents
* Observation: The problem states the cross produces 185 green-leaved fuzzywhatsits. It implies that *all* offspring were green-leaved (no yellow-striped ones appeared).
* Logic: If any parent carried a recessive gene for yellow stripes without having a dominant gene to hide it, we would see yellow offspring. To get 100% dominant phenotype (green), at least one parent must be homozygous dominant ($GG$). The other parent could be anything ($GG$, $Gg$, or $gg$), but usually, in these textbook problems, if the other trait isn't mentioned as appearing, we assume the simplest cross that guarantees the result or that the other parent was also pure dominant. However, the most definitive answer based on "produces 185 green" (implying uniformity) is that at least one parent is Homozygous Dominant (GG).
* *Note:* Without seeing any yellow offspring, we cannot determine the second parent's genotype with certainty, but the most common answer expected here is that both parents are Homozygous Dominant (GG) or one is GG and the other is Gg/gg. Given the phrasing, GG x GG or GG x gg are likely intended. Let's look at question 6. Question 6 asks about crossing the *offspring* from this cross. If the parents were $GG \times gg$, the offspring are all $Gg$. If parents were $GG \times GG$, offspring are all $GG$.
* Let's assume the standard Mendelian setup where "Green" is dominant. If the result is 100% Green, one parent is definitely GG.
6) Crossing two green-leaved fuzzywhatsits from the initial cross
* *Assumption:* Based on typical genetics problems, if the first cross resulted in uniform green offspring, those offspring are likely Heterozygous ($Gg$) resulting from a $GG \times gg$ cross, OR Homozygous ($GG$) from a $GG \times GG$ cross.
* *Scenario A (Most Likely for Practice):* If the initial parents were Pure Green ($GG$) and Yellow ($gg$), the offspring are all Hybrid Green ($Gg$).
* Cross: $Gg \times Gg$.
* Genotypes: 25% $GG$, 50% $Gg$, 25% $gg$.
* Phenotypes: 75% Green-leaved, 25% Yellow-striped.
* *Scenario B:* If the initial parents were both Pure Green ($GG$), the offspring are $GG$.
* Cross: $GG \times GG$.
* Result: 100% Green.
* *Decision:* Usually, these problems set up a hybrid cross for part 6. I will provide the answer for the Hybrid Cross ($Gg \times Gg$) as it demonstrates Mendelian ratios, which is the point of the worksheet.
* Genotypes: 1 $GG$ : 2 $Gg$ : 1 $gg$
* Phenotypes: 3 Green-leaved : 1 Yellow-striped
7) Wrinkle-seeded (Recessive) x Pure Round-seeded (Dominant)
* Alleles: $R$ = Round (Dominant), $r$ = Wrinkle (Recessive).
* Parents: Wrinkle ($rr$) $\times$ Pure Round ($RR$).
* Cross: $rr \times RR$
* Offspring: 100% $Rr$ (Heterozygous).
* Genotypic Ratio: 100% $Rr$ (or 1:0).
* Phenotypic Ratio: 100% Round seeds (or 1:0).
* Appearance: All plants will have round seeds.
8) Deafness in Dogs (Testing the Male)
* Alleles: $D$ = Hearing (Dominant), $d$ = Deaf (Recessive).
* Male: Hearing, so he is $D?$ (could be $DD$ or $Dd$).
* Female: Deaf, so she is $dd$.
* Possible Cross 1 (If Male is $DD$):
* $DD \times dd \rightarrow$ All offspring are $Dd$ (Hearing).
* Result: 100% Hearing, 0% Deaf.
* Possible Cross 2 (If Male is $Dd$):
* $Dd \times dd \rightarrow$ Offspring are 50% $Dd$ (Hearing) and 50% $dd$ (Deaf).
* Result: 50% Hearing, 50% Deaf.
9) How to tell the genotype of the male dog?
* Look at the puppies born from the test breeding in Question 8.
* If any puppy is born deaf ($dd$), the father must have contributed a recessive $d$ allele. Therefore, the father is Heterozygous ($Dd$).
* If all puppies can hear, the father is likely Homozygous Dominant ($DD$) (though you need a large enough litter to be sure statistically).
10) Two hearing dogs producing deaf offspring
* For two hearing dogs ($D?$) to produce a deaf puppy ($dd$), both parents must carry the recessive gene.
* Therefore, both parents must be Heterozygous ($Dd$).
* Punnett Square: $Dd \times Dd$
* Top: $D$, $d$
* Side: $D$, $d$
* Boxes: $DD$, $Dd$, $Dd$, $dd$
* Result: The $dd$ box represents the deaf offspring. This shows it is possible for two hearing parents to have a deaf baby if they are both carriers.
──────────────────────────────────────
Final Answer:
1) 0%
2) 0%
3) See Punnett Square below:
| | H | h |
|---|---|---|
| h | Hh | hh |
| h | Hh | hh |
4) Genotypes: 50% Hh, 50% hh. Phenotypes: 50% Have Horns, 50% No Horns.
5) At least one parent is Homozygous Dominant (GG). (Likely GG x GG or GG x gg).
6) Assuming the parents in #5 produced hybrid offspring (Gg): Genotypes: 25% GG, 50% Gg, 25% gg. Phenotypes: 75% Green-leaved, 25% Yellow-striped.
7) Genotypic Ratio: 100% Rr. Phenotypic Ratio: 100% Round. Appearance: All round seeds.
8)
* If Male is DD: 100% Hearing, 0% Deaf.
* If Male is Dd: 50% Hearing, 50% Deaf.
9) If any deaf puppies are born, the male is Dd (heterozygous). If all puppies hear, he is likely DD (homozygous dominant).
10) Both parents must be Heterozygous (Dd). The Punnett square yields 25% DD, 50% Dd, and 25% dd (deaf).
1) Percentage of offspring with short whiskers (Heterozygous x Homozygous Dominant)
* Parents: One is homozygous dominant ($WW$) and the other is heterozygous ($Ww$).
* Cross: $WW \times Ww$
* Offspring Genotypes: All offspring will receive a big $W$ from the first parent. They will receive either a big $W$ or little $w$ from the second. This results in 50% $WW$ and 50% $Ww$.
* Phenotypes: Since $W$ (long whiskers) is dominant, both $WW$ and $Ww$ result in long whiskers. There are no offspring with the genotype $ww$ (short whiskers).
* Answer: 0%
2) Percentage of offspring with short whiskers (Pure Long x Short)
* Parents: Pure long-whiskered ($WW$) crossed with short-whiskered ($ww$).
* Cross: $WW \times ww$
* Offspring Genotypes: Every single offspring gets a $W$ from one parent and a $w$ from the other. Result: 100% $Ww$.
* Phenotypes: Because they all have the dominant $W$, they all have long whiskers. None have short whiskers.
* Answer: 0%
3) & 4) Purple People Eaters (Hybrid x No Horns)
* Alleles: Let's use $H$ for horns (dominant) and $h$ for no horns (recessive).
* Parents: Hybrid ($Hh$) $\times$ No horns ($hh$).
* Punnett Square Results:
* Top row ($H$, $h$) vs Side column ($h$, $h$).
* Box 1: $Hh$
* Box 2: $hh$
* Box 3: $Hh$
* Box 4: $hh$
* Summary of Genotypes: 50% $Hh$, 50% $hh$.
* Summary of Phenotypes: 50% Have horns, 50% Do not have horns.
5) Genotypes of Green-leafed Fuzzywhatsit Parents
* Observation: The problem states the cross produces 185 green-leaved fuzzywhatsits. It implies that *all* offspring were green-leaved (no yellow-striped ones appeared).
* Logic: If any parent carried a recessive gene for yellow stripes without having a dominant gene to hide it, we would see yellow offspring. To get 100% dominant phenotype (green), at least one parent must be homozygous dominant ($GG$). The other parent could be anything ($GG$, $Gg$, or $gg$), but usually, in these textbook problems, if the other trait isn't mentioned as appearing, we assume the simplest cross that guarantees the result or that the other parent was also pure dominant. However, the most definitive answer based on "produces 185 green" (implying uniformity) is that at least one parent is Homozygous Dominant (GG).
* *Note:* Without seeing any yellow offspring, we cannot determine the second parent's genotype with certainty, but the most common answer expected here is that both parents are Homozygous Dominant (GG) or one is GG and the other is Gg/gg. Given the phrasing, GG x GG or GG x gg are likely intended. Let's look at question 6. Question 6 asks about crossing the *offspring* from this cross. If the parents were $GG \times gg$, the offspring are all $Gg$. If parents were $GG \times GG$, offspring are all $GG$.
* Let's assume the standard Mendelian setup where "Green" is dominant. If the result is 100% Green, one parent is definitely GG.
6) Crossing two green-leaved fuzzywhatsits from the initial cross
* *Assumption:* Based on typical genetics problems, if the first cross resulted in uniform green offspring, those offspring are likely Heterozygous ($Gg$) resulting from a $GG \times gg$ cross, OR Homozygous ($GG$) from a $GG \times GG$ cross.
* *Scenario A (Most Likely for Practice):* If the initial parents were Pure Green ($GG$) and Yellow ($gg$), the offspring are all Hybrid Green ($Gg$).
* Cross: $Gg \times Gg$.
* Genotypes: 25% $GG$, 50% $Gg$, 25% $gg$.
* Phenotypes: 75% Green-leaved, 25% Yellow-striped.
* *Scenario B:* If the initial parents were both Pure Green ($GG$), the offspring are $GG$.
* Cross: $GG \times GG$.
* Result: 100% Green.
* *Decision:* Usually, these problems set up a hybrid cross for part 6. I will provide the answer for the Hybrid Cross ($Gg \times Gg$) as it demonstrates Mendelian ratios, which is the point of the worksheet.
* Genotypes: 1 $GG$ : 2 $Gg$ : 1 $gg$
* Phenotypes: 3 Green-leaved : 1 Yellow-striped
7) Wrinkle-seeded (Recessive) x Pure Round-seeded (Dominant)
* Alleles: $R$ = Round (Dominant), $r$ = Wrinkle (Recessive).
* Parents: Wrinkle ($rr$) $\times$ Pure Round ($RR$).
* Cross: $rr \times RR$
* Offspring: 100% $Rr$ (Heterozygous).
* Genotypic Ratio: 100% $Rr$ (or 1:0).
* Phenotypic Ratio: 100% Round seeds (or 1:0).
* Appearance: All plants will have round seeds.
8) Deafness in Dogs (Testing the Male)
* Alleles: $D$ = Hearing (Dominant), $d$ = Deaf (Recessive).
* Male: Hearing, so he is $D?$ (could be $DD$ or $Dd$).
* Female: Deaf, so she is $dd$.
* Possible Cross 1 (If Male is $DD$):
* $DD \times dd \rightarrow$ All offspring are $Dd$ (Hearing).
* Result: 100% Hearing, 0% Deaf.
* Possible Cross 2 (If Male is $Dd$):
* $Dd \times dd \rightarrow$ Offspring are 50% $Dd$ (Hearing) and 50% $dd$ (Deaf).
* Result: 50% Hearing, 50% Deaf.
9) How to tell the genotype of the male dog?
* Look at the puppies born from the test breeding in Question 8.
* If any puppy is born deaf ($dd$), the father must have contributed a recessive $d$ allele. Therefore, the father is Heterozygous ($Dd$).
* If all puppies can hear, the father is likely Homozygous Dominant ($DD$) (though you need a large enough litter to be sure statistically).
10) Two hearing dogs producing deaf offspring
* For two hearing dogs ($D?$) to produce a deaf puppy ($dd$), both parents must carry the recessive gene.
* Therefore, both parents must be Heterozygous ($Dd$).
* Punnett Square: $Dd \times Dd$
* Top: $D$, $d$
* Side: $D$, $d$
* Boxes: $DD$, $Dd$, $Dd$, $dd$
* Result: The $dd$ box represents the deaf offspring. This shows it is possible for two hearing parents to have a deaf baby if they are both carriers.
──────────────────────────────────────
Final Answer:
1) 0%
2) 0%
3) See Punnett Square below:
| | H | h |
|---|---|---|
| h | Hh | hh |
| h | Hh | hh |
4) Genotypes: 50% Hh, 50% hh. Phenotypes: 50% Have Horns, 50% No Horns.
5) At least one parent is Homozygous Dominant (GG). (Likely GG x GG or GG x gg).
6) Assuming the parents in #5 produced hybrid offspring (Gg): Genotypes: 25% GG, 50% Gg, 25% gg. Phenotypes: 75% Green-leaved, 25% Yellow-striped.
7) Genotypic Ratio: 100% Rr. Phenotypic Ratio: 100% Round. Appearance: All round seeds.
8)
* If Male is DD: 100% Hearing, 0% Deaf.
* If Male is Dd: 50% Hearing, 50% Deaf.
9) If any deaf puppies are born, the male is Dd (heterozygous). If all puppies hear, he is likely DD (homozygous dominant).
10) Both parents must be Heterozygous (Dd). The Punnett square yields 25% DD, 50% Dd, and 25% dd (deaf).
Parent Tip: Review the logic above to help your child master the concept of punnett square practice problems worksheet.
