Genetics Practice with Simple Monohybrid Crosses - Free Printable

Let's go through each of the genetics practice problems step by step.

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1. For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho)

Definitions:
- Homozygous (Ho): Both alleles are the same (e.g., AA or aa).
- Heterozygous (He): The two alleles are different (e.g., Aa).

Now let’s analyze each:

| Genotype | Answer |
|---------|--------|
| AA | Ho | (Both alleles are A) |
| Ee | He | (One E, one e – different) |
| Bb | He | (One B, one b – different) |
| ff | Ho | (Both alleles are f) |
| Pp | He | (One P, one p – different) |
| gg | Ho | (Both alleles are g) |
| Dd | He | (One D, one d – different) |
| HH | Ho | (Both alleles are H) |

✔ Answers:
- AA → Ho
- Ee → He
- Bb → He
- ff → Ho
- Pp → He
- gg → Ho
- Dd → He
- HH → Ho

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2. For each of the genotypes below, determine what phenotypes would be possible.

We’re told:
- Purple flowers (P) are dominant to white (p)
- Brown eyes (B) are dominant to blue (b)

#### Flowers (P = purple, p = white):
- PP → Homozygous dominant → Purple
- Pp → Heterozygous → Purple (since P is dominant)
- pp → Homozygous recessive → White

#### Eyes (B = brown, b = blue):
- BB → Homozygous dominant → Brown
- Bb → Heterozygous → Brown (since B is dominant)
- bb → Homozygous recessive → Blue

✔ Answers:
- PP → Purple
- Pp → Purple
- pp → White
- BB → Brown
- Bb → Brown
- bb → Blue

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3. For each phenotype below, list the genotypes (remember to use the letter of the dominant trait)

We're given:
- Straight hair is dominant to curly
- Let’s use S = straight (dominant), s = curly (recessive)
- Tail spikes are dominant to plain tails
- Let’s use T = spikes (dominant), t = plain (recessive)

#### Straight hair:
- Since straight is dominant, it can be either:
- SS (homozygous dominant)
- Ss (heterozygous)
- But ss would be curly.

So, genotypes for straight hair are: SS or Ss

#### Spikes:
- Spikes are dominant → so genotypes could be:
- TT or Tt
- tt would be plain tail.

So, genotypes for spikes are: TT or Tt

✔ Answers:
- Straight → SS or Ss
- Spikes → TT or Tt

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✔ Final Answers Summary:

#### Problem 1: Homozygous (Ho) or Heterozygous (He)?
- AA → Ho
- Ee → He
- Bb → He
- ff → Ho
- Pp → He
- gg → Ho
- Dd → He
- HH → Ho

#### Problem 2: Phenotypes
- PP → Purple
- Pp → Purple
- pp → White
- BB → Brown
- Bb → Brown
- bb → Blue

#### Problem 3: Genotypes from Phenotypes
- Straight → SS or Ss
- Spikes → TT or Tt

Let me know if you'd like a Punnett square or diagram explanation!