Genetics Worksheets and Printables - Free Printable

Let’s work through the worksheet step by step.

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Part 1: Vocabulary – Fill in the Blanks

We need to match each definition (1–13) with the correct term from the list (A–M).

Let’s go one by one:

1. A cross between parental organisms that have a variation in a single gene or trait.
→ That’s a *monohybrid cross* → G

2. A cross between parental organisms that differ in two different traits.
→ That’s a *dihybrid cross* → I

3. Square diagram used to predict genotypes of mated individuals.
→ That’s a *Punnett square* → L

4. A basic unit of hereditary information.
→ That’s a *gene* → A

5. A characteristic or attribute associated with a gene.
→ That’s a *trait* → M

6. A variation of a gene.
→ That’s an *allele* → H

7. Type of allele that solely produces an observed trait.
→ That’s *dominant* → C

8. An allele with masked effects.
→ That’s *recessive* → D

9. Inheriting different alleles of a given gene from each parent.
→ That’s *heterozygous* → B

10. Inheriting the same alleles of a given gene from each parent.
→ That’s *homozygous* → K

11. The frequency of a given genotype.
→ That’s *genotypic frequency* → E

12. The frequency of physical attributes being observed.
→ That’s *phenotypic frequency* → J

13. Traits with phenotypes influenced by two or more genes.
→ That’s *polygenic traits* → F

✔ So the answers are:
1-G, 2-I, 3-L, 4-A, 5-M, 6-H, 7-C, 8-D, 9-B, 10-K, 11-E, 12-J, 13-F

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Part 2: Determine the genotypic frequencies

We’re given three small Punnett squares and one big dihybrid cross.

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First Square: H x H

Parents: HH x HH
Offspring: All HH

So:
- HH: 4/4 = 100% → 4
- Hh: 0 → 0
- hh: 0 → 0

Wait — actually, looking at the square:

Top row: H and h
Left column: H and H

So the four boxes are:
- Top-left: H + H = HH
- Top-right: H + h = Hh
- Bottom-left: H + H = HH
- Bottom-right: H + h = Hh

So:
- HH: 2 out of 4 → 2
- Hh: 2 out of 4 → 2
- hh: 0 → 0

But wait — the left side says “H” and “H”, top says “H” and “h”. So yes:

Boxes:
1. H (from left) + H (from top) = HH
2. H (from left) + h (from top) = Hh
3. H (from left) + H (from top) = HH
4. H (from left) + h (from top) = Hh

So:
→ HH: 2
→ Hh: 2
→ hh: 0

But the question asks for “genotypic frequencies” — probably meaning count how many of each genotype appear in the 4-box grid.

So:
HH: 2
Hh: 2
hh: 0

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Second Square: A x a

Parents: Aa x aa? Wait — let’s look:

Top: a and a
Left: A and a

So:

Boxes:
1. A + a = Aa
2. A + a = Aa
3. a + a = aa
4. a + a = aa

So:
→ AA: 0
→ Aa: 2
→ aa: 2

But again, the question lists:
AA: ___
Aa: ___
aa: ___

So:
AA: 0
Aa: 2
aa: 2

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Third Square: B x b

Top: B and b
Left: B and b

So:

Boxes:
1. B + B = BB
2. B + b = Bb
3. b + B = Bb
4. b + b = bb

So:
→ BB: 1
→ Bb: 2
→ bb: 1

Thus:
BB: 1
Bb: 2
bb: 1

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Fourth Part: Dihybrid Cross (YYRR x yyrr?)

Actually, looking at the big Punnett square on the bottom right:

It shows gametes: YR, Yr, yR, yr on both axes.

And the offspring genotypes are filled in.

We need to count how many times each genotype appears in the 16-box grid.

List of genotypes to count:

- YYRR
- YYRr
- YYrr
- YyRR
- YyRr
- Yyrr
- yyRR
- yyRr
- yyrr

Let’s go row by row.

Row 1 (YR gamete):
- YR + YR = YYRR
- YR + Yr = YYRr
- YR + yR = YyRR
- YR + yr = YyRr

Row 2 (Yr gamete):
- Yr + YR = YYRr
- Yr + Yr = YYrr
- Yr + yR = YyRr
- Yr + yr = Yyrr

Row 3 (yR gamete):
- yR + YR = YyRR
- yR + Yr = YyRr
- yR + yR = yyRR
- yR + yr = yyRr

Row 4 (yr gamete):
- yr + YR = YyRr
- yr + Yr = Yyrr
- yr + yR = yyRr
- yr + yr = yyrr

Now let’s tally:

YYRR: only 1 time (top-left) → 1

YYRr: appears in row1 col2, row2 col1 → 2

YYrr: row2 col2 → 1

YyRR: row1 col3, row3 col1 → 2

YyRr: row1 col4, row2 col3, row3 col2, row4 col1 → 4

Yyrr: row2 col4, row4 col2 → 2

yyRR: row3 col3 → 1

yyRr: row3 col4, row4 col3 → 2

yyrr: row4 col4 → 1

Let me double-check total: 1+2+1+2+4+2+1+2+1 = 16 → correct.

So final counts:

YYRR: 1
YYRr: 2
YYrr: 1
YyRR: 2
YyRr: 4
Yyrr: 2
yyRR: 1
yyRr: 2
yyrr: 1

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Final Answers:

Vocabulary:
1. G
2. I
3. L
4. A
5. M
6. H
7. C
8. D
9. B
10. K
11. E
12. J
13. F

Genotypic Frequencies:

First square (H/h):
HH: 2
Hh: 2
hh: 0

Second square (A/a):
AA: 0
Aa: 2
aa: 2

Third square (B/b):
BB: 1
Bb: 2
bb: 1

Dihybrid cross:
YYRR: 1
YYRr: 2
YYrr: 1
YyRR: 2
YyRr: 4
Yyrr: 2
yyRR: 1
yyRr: 2
yyrr: 1

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Final Answer:
1. G
2. I
3. L
4. A
5. M
6. H
7. C
8. D
9. B
10. K
11. E
12. J
13. F
HH: 2, Hh: 2, hh: 0
AA: 0, Aa: 2, aa: 2
BB: 1, Bb: 2, bb: 1
YYRR: 1, YYRr: 2, YYrr: 1, YyRR: 2, YyRr: 4, Yyrr: 2, yyRR: 1, yyRr: 2, yyrr: 1