Mendelian Genetics Worksheet Answer Key Inspirational Genetics ... - Free Printable

It looks like you've uploaded a worksheet titled "Punnett Square Fun" with four genetics problems involving Punnett squares. I’ll go through each question, solve it step by step, and explain the reasoning clearly.

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Question 1: Purple People Eaters

> In Purple People Eaters, having two horns is dominant over having no horns, which is recessive. Draw a Punnett Square showing the cross of a purple people eater that is heterozygous for horns with a Purple People Eater that has two horns. Summarize the genotypes and phenotypes of the possible offspring.

#### Step-by-step:
- Let’s define the alleles:
- H = two horns (dominant)
- h = no horns (recessive)

- Parent 1: Heterozygous → Hh
- Parent 2: Has two horns → Could be HH or Hh, but since we're told it's a "Purple People Eater that has two horns", and no info about being purebred, we assume it could be either. But in most such problems, if not specified, and one parent is heterozygous, the other is often assumed to be homozygous dominant unless stated otherwise. However, let's look at the answer key provided:

> Answer Key says:
> - Offspring genotypes: 50% HH, 50% Hh
> - Phenotypes: 100% have horns

This implies that the second parent must be HH (homozygous dominant), because only then would all offspring have horns.

So:
- Parent 1: Hh
- Parent 2: HH

Now make the Punnett square:

| | H | H |
|-------|-------|-------|
| H | HH | HH |
| h | Hh | Hh |

Offspring:
- Genotypes: 50% HH, 50% Hh
- Phenotypes: All have horns (since H is dominant)

✔ So the answer matches the key.

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Question 2: Love Bug Antennae

> Love Bugs may have straight antennae or curly ones. The Love Bug pictured here, Sweetie, has the offspring of two straight antennae parents. Based on that information, what do you know about the inheritance of antennae shape in Love Bugs? What is Sweetie’s genotype? Draw a Punnett Square to show the cross that produced Sweetie. What is the chance that her siblings will have curly antennae like her?

#### Step-by-step:
- Sweetie has curly antennae, but both parents had straight antennae.
- This means curly antennae must be recessive, because two parents with dominant traits can produce a recessive offspring only if both are carriers.

Let’s define:
- S = straight antennae (dominant)
- s = curly antennae (recessive)

Since both parents have straight antennae but produced a curly-antennae child, both must be heterozygous (Ss).

So:
- Parent 1: Ss
- Parent 2: Ss

Punnett square:

| | S | s |
|-------|-------|-------|
| S | SS | Ss |
| s | Ss | ss |

Offspring:
- Genotypes: 25% SS, 50% Ss, 25% ss
- Phenotypes: 75% straight, 25% curly

Sweetie has curly antennae → genotype: ss

Now, the question asks: *What is the chance that her siblings will have curly antennae like her?*

Answer: 25% (since 25% of offspring are expected to be ss).

✔ Matches the answer key: "There is a 25% chance that her siblings will have curly antennae like her."

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Question 3: Smiley Cats Whiskers

> Long whiskers are dominant over short whiskers in Smiley Cats. What percentage of offspring is expected to have short whiskers if the cross of two long-whiskered Smiley Cats, one dominant and one that is heterozygous?

Wait — let's read carefully:
> “one dominant and one that is heterozygous”

But “dominant” likely means homozygous dominant, so:

- Parent 1: LL (homozygous dominant)
- Parent 2: Ll (heterozygous)

Define:
- L = long whiskers (dominant)
- l = short whiskers (recessive)

Punnett square:

| | L | l |
|-------|-------|-------|
| L | LL | Ll |
| L | LL | Ll |

Offspring:
- Genotypes: 50% LL, 50% Ll
- Phenotypes: All have long whiskers (no short whiskers)

So 0% of offspring will have short whiskers.

But the answer key says: "There is a 25% chance of these offspring having short whiskers."

That suggests a contradiction.

Wait — perhaps there was a typo in the question?

Let’s re-read:
> “the cross of two long-whiskered Smiley Cats, one dominant and one that is heterozygous”

But if one is homozygous dominant (LL) and the other is heterozygous (Ll), then no short whiskers should appear.

But the answer key says 25% — that happens only if both parents are heterozygous (Ll x Ll).

So likely, the intended meaning is:
> “two long-whiskered cats, one homozygous dominant and one heterozygous” → but this gives 0% short.

But answer key says 25% → so probably the question meant:
> “one heterozygous and one heterozygous”, or possibly “one is heterozygous and the other is unknown, but the answer assumes both are heterozygous.”

Alternatively, maybe the phrase “one dominant and one that is heterozygous” is poorly worded.

But if both parents are long-whiskered, and they produce offspring with short whiskers, then both must carry the recessive allele.

So likely, the correct interpretation is:
> Both parents are long-whiskered, but one is homozygous dominant (LL), the other is heterozygous (Ll) → then no short whiskers.

But answer key says 25% → so contradiction.

Wait — perhaps the question is asking:
> “If the cross is between two long-whiskered cats, one of which is heterozygous, and the other is also heterozygous?”

Then:

- Ll × Ll → 25% ll → 25% short whiskers

That matches the answer key.

So probably the question meant:
> “The cross of two long-whiskered Smiley Cats, both of whom are heterozygous.”

But it says “one dominant and one that is heterozygous” — which would be LL × Ll → no short whiskers.

So there's an error in either the question or the key.

But since the answer key says 25%, we assume the intended cross is Ll × Ll.

So:
- Parents: Ll × Ll
- Punnett square:

| | L | l |
|-------|-------|-------|
| L | LL | Ll |
| l | Ll | ll |

→ 25% ll → short whiskers

✔ So 25% chance for short whiskers.

Thus, the question likely contains a typo, and should say:
> “the cross of two long-whiskered Smiley Cats, both of which are heterozygous”

Or “one is heterozygous and the other is also heterozygous”.

But as written, “one dominant (LL) and one heterozygous (Ll)” → 0% short whiskers.

But since the answer key says 25%, we go with Ll × Ll.

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Question 4: Wings in Critters

> The presence of wings in Critters is a dominant trait. How could you determine the genotype of a winged Critter? Don’t forget to create a Punnett square to help explain your answer.

#### Step-by-step:
- Winged = dominant → W
- No wings = recessive → w
- A winged critter could be WW or Ww
- To determine its genotype, perform a test cross with a homozygous recessive (no wings) → ww

Test Cross:
- Cross winged critter (unknown: WW or Ww) with ww

Case 1: If winged parent is WW
- Cross: WW × ww
- All offspring: Ww → all have wings

Case 2: If winged parent is Ww
- Cross: Ww × ww
- Offspring: 50% Ww (winged), 50% ww (no wings)

So:
- If all offspring have wings → parent is WW
- If about 50% have wings, 50% don't → parent is Ww

This is the test cross method.

Punnett squares:

Option 1: WW × ww

| | w | w |
|-------|-------|-------|
| W | Ww | Ww |
| W | Ww | Ww |

→ All offspring: Ww → all winged

Option 2: Ww × ww

| | w | w |
|-------|-------|-------|
| W | Ww | Ww |
| w | ww | ww |

→ 50% Ww (winged), 50% ww (no wings)

✔ So, to determine the genotype of a winged critter, cross it with a non-winged (ww) critter.

- If all offspring have wings → genotype is WW
- If half have wings, half don’t → genotype is Ww

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✔ Final Summary of Answers:

1. Purple People Eaters:
- Cross: Hh × HH
- Offspring: 50% HH, 50% Hh → all have horns

2. Love Bug Antennae:
- Curly antennae is recessive (ss)
- Parents: Ss × Ss
- Sweetie’s genotype: ss
- Chance siblings have curly antennae: 25%

3. Smiley Cats Whiskers:
- Likely intended cross: Ll × Ll
- 25% chance of short whiskers (ll)

4. Winged Critters:
- Use test cross with ww (no wings)
- If all offspring winged → WW
- If 50% winged, 50% not → Ww

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