Genotype and Phenotypes worksheet - Free Printable

Let’s go step by step through each part of the worksheet.

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Part 2 (First Table): For each genotype, indicate whether it is heterozygous, homozygous dominant, or homozygous recessive.

Remember:
- Homozygous dominant = two capital letters (like AA)
- Heterozygous = one capital and one lowercase (like Aa)
- Homozygous recessive = two lowercase letters (like aa)

Now let’s fill in each:

Left column:
- AA → both capitals → homozygous dominant
- Bb → one cap, one lower → heterozygous
- Cc → one cap, one lower → heterozygous
- Dd → one cap, one lower → heterozygous

Right column:
- Ee → one cap, one lower → heterozygous
- ff → both lowercase → homozygous recessive
- GG → both capitals → homozygous dominant
- HH → both capitals → homozygous dominant

Bottom left:
- Ii → one cap, one lower → heterozygous
- Jj → one cap, one lower → heterozygous
- kk → both lowercase → homozygous recessive
- Ll → one cap, one lower → heterozygous

Bottom right:
- Mm → one cap, one lower → heterozygous
- nn → both lowercase → homozygous recessive
- OO → both capitals → homozygous dominant
- Pp → one cap, one lower → heterozygous

✔ All checked — no mistakes.

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Part 2 (Second Table): For each genotype, determine the phenotype.

We’re told which trait is dominant. Remember: if there’s at least one dominant allele (capital letter), the organism shows the dominant trait. Only if both are recessive (lowercase) do they show the recessive trait.

Purple flowers (P) dominant to white (p)
→ PP → purple
→ Pp → purple (because P is dominant)
→ pp → white

Brown eyes (B) dominant to blue (b)
→ BB → brown
→ Bb → brown
→ bb → blue

Round seeds (R) dominant to wrinkled (r)
→ RR → round
→ Rr → round
→ rr → wrinkled

Bobtails (t) recessive (long tails T dominant)
→ TT → long tail (dominant)
→ Tt → long tail (still has T)
→ tt → bobtail (only when both are t)

✔ Double-checked — all correct.

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Part 3: For each phenotype, list the genotypes.

We’re given traits and told which letter is dominant. We need to write which genotypes give which phenotype.

Straight hair (S) dominant to curly (s)
→ Straight hair happens with: SS or Ss (any with at least one S)
→ Curly hair only with: ss (both recessive)

So for “straight” → SS, Ss
For “curly” → ss

But looking at the table, it lists:

Left side:
Ss SS ss → straight
Ss SS ss → curly

Wait — that doesn’t make sense as written. Let me re-read.

Actually, the table says:

> Straight hair is dominant (S) to curly (s)
> Then below:
> Ss SS ss straight
> Ss SS ss curly

That seems like a mistake in how it’s laid out. Probably meant:

Under “straight”, you should list the genotypes that produce straight hair: SS and Ss
Under “curly”, you should list: ss

Same for the other side:

Pointed heads (H) dominant to round heads (h)
→ Pointed: HH or Hh
→ Round: hh

The table shows:

HH Hh hh pointed
HH Hh hh round

Again, probably meant:

Under “pointed” → HH, Hh
Under “round” → hh

So we’ll fix that based on genetics rules.

✔ Confirmed — this matches standard Mendelian inheritance.

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Final Answer:

Part 2 (Genotype Classification):

AA – homozygous dominant
Bb – heterozygous
Cc – heterozygous
Dd – heterozygous
Ee – heterozygous
ff – homozygous recessive
GG – homozygous dominant
HH – homozygous dominant
Ii – heterozygous
Jj – heterozygous
kk – homozygous recessive
Ll – heterozygous
Mm – heterozygous
nn – homozygous recessive
OO – homozygous dominant
Pp – heterozygous

Part 2 (Phenotype Determination):

Purple flowers:
PP – purple
Pp – purple
pp – white

Brown eyes:
BB – brown
Bb – brown
bb – blue

Round seeds:
RR – round
Rr – round
rr – wrinkled

Bobtails:
TT – long tail
Tt – long tail
tt – bobtail

Part 3 (Genotypes for Phenotypes):

Straight hair: SS, Ss
Curly hair: ss

Pointed heads: HH, Hh
Round heads: hh