Monohybrid Cross Practice Problems - Free Printable

Problem Analysis:

The task involves solving Punnett Square problems for three different scenarios. A Punnett Square is a tool used in genetics to predict the genotype and phenotype of offspring from a cross between two parents. Here's how we will approach each problem:

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1. Flower Color in Snapdragons

#### Given:
- The allele for purple color (`C`) is dominant over the allele for white color (`c`).
- Parents: Homozygous dominant male (`CC`) and homozygous recessive female (`cc`).

#### Steps:
1. Identify the alleles of the parents:
- Male parent: `CC` (purple, dominant)
- Female parent: `cc` (white, recessive)

2. Set up the Punnett Square:
- The male parent contributes either `C` or `C` (since it is homozygous dominant).
- The female parent contributes either `c` or `c` (since it is homozygous recessive).

| | `C` | `C` |
|-----|-----|-----|
| `c` | `Cc`| `Cc`|
| `c` | `Cc`| `Cc`|

3. Determine the genotypes and phenotypes:
- All offspring have the genotype `Cc`.
- Since `C` (purple) is dominant over `c` (white), all offspring will have the phenotype "purple."

#### Results:
- Ratio: 4:0 (all purple)
- Genotype: `Cc`
- Phenotype: Purple

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2. Fur Length in Guinea Pigs

#### Given:
- The allele for long fur (`L`) is dominant over the allele for short fur (`l`).
- Parents: Heterozygous male (`Ll`) and homozygous recessive female (`ll`).

#### Steps:
1. Identify the alleles of the parents:
- Male parent: `Ll` (heterozygous, long fur)
- Female parent: `ll` (homozygous recessive, short fur)

2. Set up the Punnett Square:
- The male parent contributes either `L` or `l`.
- The female parent contributes either `l` or `l`.

| | `L` | `l` |
|-----|-----|-----|
| `l` | `Ll`| `ll`|
| `l` | `Ll`| `ll`|

3. Determine the genotypes and phenotypes:
- Offspring genotypes: `Ll`, `Ll`, `ll`, `ll`.
- Phenotypes:
- `Ll`: Long fur (dominant)
- `ll`: Short fur (recessive)

#### Results:
- Ratio: 2:2 (1:1 simplified ratio of long fur to short fur)
- Genotypes: `Ll`, `ll`
- Phenotypes: Long fur, Short fur

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3. Eye Color in Mice

#### Given:
- The allele for black eyes (`B`) is dominant over the allele for brown eyes (`b`).
- Parents: Heterozygous male (`Bb`) and heterozygous female (`Bb`).

#### Steps:
1. Identify the alleles of the parents:
- Male parent: `Bb` (heterozygous, black eyes)
- Female parent: `Bb` (heterozygous, black eyes)

2. Set up the Punnett Square:
- The male parent contributes either `B` or `b`.
- The female parent contributes either `B` or `b`.

| | `B` | `b` |
|-----|-----|-----|
| `B` | `BB`| `Bb`|
| `b` | `Bb`| `bb`|

3. Determine the genotypes and phenotypes:
- Offspring genotypes: `BB`, `Bb`, `Bb`, `bb`.
- Phenotypes:
- `BB` and `Bb`: Black eyes (dominant)
- `bb`: Brown eyes (recessive)

#### Results:
- Ratio: 3:1 (black eyes : brown eyes)
- Genotypes: `BB`, `Bb`, `bb`
- Phenotypes: Black eyes, Brown eyes

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Final Answers:

1. Flower Color in Snapdragons:
- Ratio: 4:0
- Genotype: `Cc`
- Phenotype: Purple

2. Fur Length in Guinea Pigs:
- Ratio: 1:1
- Genotypes: `Ll`, `ll`
- Phenotypes: Long fur, Short fur

3. Eye Color in Mice:
- Ratio: 3:1
- Genotypes: `BB`, `Bb`, `bb`
- Phenotypes: Black eyes, Brown eyes

Final Answer Boxed:
\[
\boxed{
\begin{array}{l}
\text{1. Ratio: 4:0, Genotype: } Cc, \text{ Phenotype: Purple} \\
\text{2. Ratio: 1:1, Genotypes: } Ll, ll, \text{ Phenotypes: Long fur, Short fur} \\
\text{3. Ratio: 3:1, Genotypes: } BB, Bb, bb, \text{ Phenotypes: Black eyes, Brown eyes}
\end{array}
}
\]