Genetics practice worksheet with Punnett squares for flower color inheritance.

Let’s solve this step by step.

We are given two genetics problems involving pea plants. Each problem has two traits: seed color and flower color. We’re told which alleles are dominant and recessive, and we’re crossing two heterozygous parents for both traits (dihybrid cross). Then we need to fill in Punnett squares and answer questions about offspring phenotypes.

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Problem 1:

Traits:
- Seed color: Yellow (Y) is dominant over green (y)
- Flower color: Purple (P) is dominant over white (p)

Parent 1 genotype: YyPp
Parent 2 genotype: YyPp

This is a standard dihybrid cross: YyPp × YyPp

Each parent can produce 4 types of gametes: YP, Yp, yP, yp

So the Punnett square will be 4x4 = 16 boxes.

Let’s list all possible combinations from the cross:

Gametes from Parent 1 (top): YP, Yp, yP, yp
Gametes from Parent 2 (side): YP, Yp, yP, yp

Now fill in the 16 offspring genotypes:

Row 1 (YP x ...):
- YP x YP → YYPP
- YP x Yp → YYPp
- YP x yP → YyPP
- YP x yp → YyPp

Row 2 (Yp x ...):
- Yp x YP → YYPp
- Yp x Yp → YYpp
- Yp x yP → YyPp
- Yp x yp → Yypp

Row 3 (yP x ...):
- yP x YP → YyPP
- yP x Yp → YyPp
- yP x yP → yyPP
- yP x yp → yyPp

Row 4 (yp x ...):
- yp x YP → YyPp
- yp x Yp → Yypp
- yp x yP → yyPp
- yp x yp → yypp

Now let’s count phenotypes.

Phenotype rules:
- Yellow seeds: at least one Y (YY or Yy)
- Green seeds: only yy
- Purple flowers: at least one P (PP or Pp)
- White flowers: only pp

So:

1. Yellow seeds and purple flowers: Must have Y_ and P_
Let’s count how many of the 16 have both:

From above:

YYPP → yellow/purple
YYPp → yellow/purple
YyPP → yellow/purple
YyPp → yellow/purple
YYPp → yellow/purple
YYpp → yellow/white ← not counted
YyPp → yellow/purple
Yypp → yellow/white ← not counted
YyPP → yellow/purple
YyPp → yellow/purple
yyPP → green/purple ← not counted
yyPp → green/purple ← not counted
YyPp → yellow/purple
Yypp → yellow/white ← not counted
yyPp → green/purple ← not counted
yypp → green/white ← not counted

Better way: In a standard dihybrid cross (YyPp x YyPp), the phenotype ratio is:

9 : 3 : 3 : 1

Where:
- 9 = yellow/purple (Y_P_)
- 3 = yellow/white (Y_pp)
- 3 = green/purple (yyP_)
- 1 = green/white (yypp)

Yes! That’s the classic Mendelian dihybrid ratio.

So for Problem 1:

Total offspring: 16

→ Yellow seeds and purple flowers: 9
→ Yellow seeds and white flowers: 3
→ Green seeds and purple flowers: 3
→ Green seeds and white flowers: 1

That matches what we’d get if we carefully counted.

So answers for Problem 1:

How many offspring have yellow seeds and purple flowers? → 9
How many offspring have yellow seeds and white flowers? → 3
How many offspring have green seeds and purple flowers? → 3
How many offspring have green seeds and white flowers? → 1

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Problem 2:

Traits:
- Seed color: Green (G) is dominant over yellow (g) ← Note: This is reversed from Problem 1!
- Flower color: White (W) is dominant over purple (w) ← Also reversed!

Wait — let’s read carefully:

> “The first is heterozygous for seed color and homozygous recessive for flower color.”
> “Green seeds are dominant over yellow seeds while white flowers are dominant over purple flowers.”

So:

Seed color: G (green, dominant), g (yellow, recessive)
Flower color: W (white, dominant), w (purple, recessive)

Parent 1: heterozygous for seed color → Gg
and homozygous recessive for flower color → ww
So Parent 1 genotype: Ggww

Parent 2: homozygous recessive for seed color → gg
and heterozygous for flower color → Ww
So Parent 2 genotype: ggWw

Cross: Ggww × ggWw

Now, find gametes:

Parent 1 (Ggww): can make gametes: Gw, gw
(because seed allele: G or g; flower allele: only w since homozygous recessive)

Parent 2 (ggWw): can make gametes: gW, gw
(seed allele: only g; flower allele: W or w)

So Punnett square is 2x2:

Gametes from Parent 1 (top): Gw, gw
Gametes from Parent 2 (side): gW, gw

Fill in:

Top-left: Gw x gW → GgWw
Top-right: Gw x gw → Ggww
Bottom-left: gw x gW → ggWw
Bottom-right: gw x gw → ggww

Now determine phenotypes:

Recall:
- Green seeds: G_ (GG or Gg) → here, Gg is green, gg is yellow
- Yellow seeds: gg
- White flowers: W_ (WW or Ww) → here, Ww is white, ww is purple
- Purple flowers: ww

So:

1. GgWw → green seeds, white flowers
2. Ggww → green seeds, purple flowers
3. ggWw → yellow seeds, white flowers
4. ggww → yellow seeds, purple flowers

Each box is equally likely → 1 out of 4 each.

So:

How many offspring have green seeds and white flowers? → 1 (GgWw)
How many offspring have green seeds and purple flowers? → 1 (Ggww)
How many offspring have yellow seeds and white flowers? → 1 (ggWw)
How many offspring have yellow seeds and purple flowers? → 1 (ggww)

Since it’s a 2x2 grid, total 4 offspring possibilities, each appearing once.

But wait — the worksheet says “how many offspring” — probably assuming 4 total, as per the 2x2 Punnett square shown.

Looking at the image description (even though I’m not describing it), the second Punnett square is drawn with 4 boxes (2x2), so yes, 4 total offspring.

Thus, each phenotype appears exactly once.

Answers for Problem 2:

→ Green seeds and white flowers: 1
→ Green seeds and purple flowers: 1
→ Yellow seeds and white flowers: 1
→ Yellow seeds and purple flowers: 1

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Final Answer:

For Problem 1:
- Yellow seeds and purple flowers: 9
- Yellow seeds and white flowers: 3
- Green seeds and purple flowers: 3
- Green seeds and white flowers: 1

For Problem 2:
- Green seeds and white flowers: 1
- Green seeds and purple flowers: 1
- Yellow seeds and white flowers: 1
- Yellow seeds and purple flowers: 1