Question
Using concepts of Mendelian genetics and natural selection, explain the increase in the phenotype frequency for black fur from the initial population through generation 40.
Type your answer here.
A table shows the initial population of 9 brown mice, or 90%, and 1 black mouse, or 10%.
Type your answer here.
A table shows the initial population of 9 brown mice, or 90%, and 1 black mouse, or 10%.
Answers
GPT-4o mini
To understand the increase in the phenotype frequency for black fur among the mouse population over 40 generations using Mendelian genetics and natural selection, we can follow several key concepts.
### Initial Population
Let’s consider the initial population consisting of 9 brown mice (90%) and 1 black mouse (10%). In Mendelian genetics, we can assume that fur color is governed by a single gene with two alleles: one for brown fur (B) that is dominant, and one for black fur (b) that is recessive. Therefore, the possible genotypes among the mice would be:
- **BB**: Homozygous dominant (brown fur)
- **Bb**: Heterozygous (brown fur)
- **bb**: Homozygous recessive (black fur)
In the initial population, it's probable that the single black mouse is of genotype **bb**, while the brown mice could be either **BB** or **Bb**.
### Generational Changes
#### 1. **Recessive Allele Frequency**:
Since black fur is the result of the recessive genotype (bb), its initial frequency in the population is low. In a population of 10 mice, the frequency of the black allele (b) can be determined by looking for how many mice show the black phenotype. Initially, the frequency of the black phenotype (1 out of 10 mice) is 10%.
#### 2. **Selection Pressures**:
Natural selection can play a crucial role in altering phenotype frequencies over generations. Suppose environmental conditions favor black-furred mice, such as better camouflage in their habitat, predators being less likely to spot them, or other survival advantages. This enhanced survival and reproductive success for black mice can contribute to an increased frequency of the b allele.
#### 3. **Reproductive Advantage**:
As the black mice survive and reproduce more successfully than the brown mice, the allele frequency shifts. Each subsequent generation sees more black mice being born as the b allele is passed on preferentially due to the survival advantage. This phenomenon aligns with the principles of natural selection, where advantageous traits become more common over time.
#### 4. **Genetic Drift**:
In addition to natural selection, genetic drift might also play a role, especially if the population is small. Random events can lead to fluctuations in allele frequencies purely by chance, which may also contribute to increasing the rate of black-furred mice.
### Phenotypic Frequency Over Generations
Now, let’s look into how these factors affect the phenotypic frequency of black fur over 40 generations. Each generation could yield the following possibilities:
- Assuming black-furred mice reproduce more successfully, we would observe a gradual increase in black fur phenomenally.
- If initially, one black mouse is bred with brown mice that could be either BB or Bb, we might have some heterozygous offspring, but as generations pass and natural selection favors black fur, the proportion of black furred mice in the population increases.
By generation 40, if these trends continue, we could potentially have a significant increase in the proportion of black-furred mice—hypothetically reaching even 50%, 70%, or beyond depending on how strong the selection pressure is.
### Conclusion
Through the lens of Mendelian genetics and natural selection, the initial low frequency of the black fur phenotype can evolve into a larger frequency over generations due to selective advantages, inheritance patterns, and potentially random genetic drift. By generation 40, we would likely observe a marked increase in the percentage of black mice, illustrating the principles of evolution in action.
### Initial Population
Let’s consider the initial population consisting of 9 brown mice (90%) and 1 black mouse (10%). In Mendelian genetics, we can assume that fur color is governed by a single gene with two alleles: one for brown fur (B) that is dominant, and one for black fur (b) that is recessive. Therefore, the possible genotypes among the mice would be:
- **BB**: Homozygous dominant (brown fur)
- **Bb**: Heterozygous (brown fur)
- **bb**: Homozygous recessive (black fur)
In the initial population, it's probable that the single black mouse is of genotype **bb**, while the brown mice could be either **BB** or **Bb**.
### Generational Changes
#### 1. **Recessive Allele Frequency**:
Since black fur is the result of the recessive genotype (bb), its initial frequency in the population is low. In a population of 10 mice, the frequency of the black allele (b) can be determined by looking for how many mice show the black phenotype. Initially, the frequency of the black phenotype (1 out of 10 mice) is 10%.
#### 2. **Selection Pressures**:
Natural selection can play a crucial role in altering phenotype frequencies over generations. Suppose environmental conditions favor black-furred mice, such as better camouflage in their habitat, predators being less likely to spot them, or other survival advantages. This enhanced survival and reproductive success for black mice can contribute to an increased frequency of the b allele.
#### 3. **Reproductive Advantage**:
As the black mice survive and reproduce more successfully than the brown mice, the allele frequency shifts. Each subsequent generation sees more black mice being born as the b allele is passed on preferentially due to the survival advantage. This phenomenon aligns with the principles of natural selection, where advantageous traits become more common over time.
#### 4. **Genetic Drift**:
In addition to natural selection, genetic drift might also play a role, especially if the population is small. Random events can lead to fluctuations in allele frequencies purely by chance, which may also contribute to increasing the rate of black-furred mice.
### Phenotypic Frequency Over Generations
Now, let’s look into how these factors affect the phenotypic frequency of black fur over 40 generations. Each generation could yield the following possibilities:
- Assuming black-furred mice reproduce more successfully, we would observe a gradual increase in black fur phenomenally.
- If initially, one black mouse is bred with brown mice that could be either BB or Bb, we might have some heterozygous offspring, but as generations pass and natural selection favors black fur, the proportion of black furred mice in the population increases.
By generation 40, if these trends continue, we could potentially have a significant increase in the proportion of black-furred mice—hypothetically reaching even 50%, 70%, or beyond depending on how strong the selection pressure is.
### Conclusion
Through the lens of Mendelian genetics and natural selection, the initial low frequency of the black fur phenotype can evolve into a larger frequency over generations due to selective advantages, inheritance patterns, and potentially random genetic drift. By generation 40, we would likely observe a marked increase in the percentage of black mice, illustrating the principles of evolution in action.