1. ចំពោះទន្សាយ លក្ខណៈរោមខ្មៅលុបលើ លក្ខណៈ រោមត្នោត លក្ខណៈរោមខ្លី លុបលើរោមវែង ។ គេបង្កាត់រោមខ្មៅវែង អូម៉ូសុីកូត ជាមួយទន្សាយរោមត្នាត ហើយរោមខ្លីអូម៉ូសុីកូត ។
  ក. តើទន្សាយនៅ ជំនាន់ទី1 F1 មានលក្ខណៈដូចម្តេច?
  ខ. បើគេបង្កាត់ ជំនាន់ទី F1 ជាមួយគ្នា តើជំនាន់ទី 2 មានលក្ខណៈដូចម្តេច ?
  គ. បើគេសង្កាត់ ទន្សាយនៅជំនាន់ ទី 1 ជាមួយទន្សាយ រោមវែង តើគេទទួលបាន ផេណូទីប ក្នុងសមាមាត្រដូចម្តេច ?
  Please tell me

To solve the genetics problem involving rabbits with different fur characteristics, we'll use the principles of Mendelian genetics, considering dominant and recessive traits.

### Part (ក): Phenotypes of the First Generation (F1)

**Given:**
- Black fur (B) is dominant over brown fur (b).
- Long fur (L) is dominant over short fur (l).
- The parent rabbits are:
  - **Black, long fur homozygous** (BBLL)
  - **Brown, short fur homozygous** (bbll)

**Cross:**
- \( \text{BBLL} \times \text{bbll} \)

**F1 Generation Genotype:**
- All offspring will receive one dominant allele from the black, long fur parent (B and L) and one recessive allele from the brown, short fur parent (b and l). Thus, all F1 offspring will have the genotype \( \text{BbLl} \).

**F1 Generation Phenotype:**
- Since B (black) and L (long) are dominant, all F1 rabbits will have **black, long fur**.

### Part (ខ): Phenotypes of the Second Generation (F2)

**Crossing F1 Generation:**
- \( \text{BbLl} \times \text{BbLl} \)

**Genotype Distribution:**
We need to consider each trait separately and then combine the results using the dihybrid cross method:

1. **Fur Color (B, b):**
   - BB, Bb, and bb in the ratio 1:2:1

2. **Fur Length (L, l):**
   - LL, Ll, and ll in the ratio 1:2:1

**Phenotypic Ratios:**
- To find the phenotypic ratio, we calculate the product of the individual probabilities for each trait:

1. **Black, long fur (BBLL, BBLl, BbLL, BbLl):**  
   Probability: \( \frac{3}{4} \times \frac{3}{4} = \frac{9}{16} \)

2. **Black, short fur (BBll, Bbll):**  
   Probability: \( \frac{3}{4} \times \frac{1}{4} = \frac{3}{16} \)

3. **Brown, long fur (bbLL, bbLl):**  
   Probability: \( \frac{1}{4} \times \frac{3}{4} = \frac{3}{16} \)

4. **Brown, short fur (bbll):**  
   Probability: \( \frac{1}{4} \times \frac{1}{4} = \frac{1}{16} \)

Thus, the phenotypic ratio in the F2 generation is **9:3:3:1**:
- 9 Black, long fur
- 3 Black, short fur
- 3 Brown, long fur
- 1 Brown, short fur

### Part (គ): Cross of F1 Generation with Long Fur Rabbit

**Given:**
- F1 rabbits (BbLl) crossed with a rabbit with long fur (assuming homozygous long, so LL or Ll).
- Assume the rabbit is **homozygous for long fur (LL)**.

**Cross:**
- \( \text{BbLl} \times \text{bbLL} \)

**Phenotypic Ratios:**
- **Black, long fur (BbLL, BbLl):**  
  All offspring with at least one dominant B allele and at least one L allele will have black, long fur.

- **Brown, long fur (bbLL, bbLl):**  
  Offspring with two recessive b alleles and at least one L allele will have brown, long fur.

Calculating the probabilities:
1. **BbLL (Black, long fur):** \( \frac{1}{2} \times 1 = \frac{1}{2} \)
2. **BbLl (Black, long fur):** \( \frac{1}{2} \times 0 = 0 \)
3. **bbLL (Brown, long fur):** \( \frac{1}{2} \times 1 = \frac{1}{2} \)
4. **bbLl (Brown, long fur):** \( \frac{1}{2} \times 0 = 0 \)

Thus, the phenotypic ratio will be:
- **1:1 for Black, long fur and Brown, long fur.**

### Questions and Tip

Would you like to clarify or discuss any specific part of the solution in more detail? Here are some related questions:

1. What are dominant and recessive alleles?
2. How do you use a Punnett square to determine the genotypes of offspring?
3. What is a dihybrid cross, and how does it differ from a monohybrid cross?
4. How does the principle of independent assortment apply to this problem?
5. What are some examples of epistasis in genetics?
6. How does incomplete dominance differ from complete dominance?
7. What are the phenotypic ratios for a trihybrid cross?
8. How do environmental factors influence gene expression?

**Tip:** When solving genetic problems, it is crucial to clearly define dominant and recessive traits and use Punnett squares to visualize the possible genotypes and phenotypes of offspring.

Learn how to solve genetics problems involving rabbits with different fur characteristics using Mendelian genetics principles. This problem covers dominant and recessive traits, Punnett squares, and genotype and phenotype ratios in the context of rabbit fur color and length inheritance. Suitable for high school students and those interested in genetics.

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