In laboratory mice, gray coat color (G) is dominant over albino coat color (g). Cross a female Gg with a male gg. What is the probability of getting gray offspring? What is the probability of getting an albino mouse in the above cross? What are the phenotypes of the parents in the above cross?
The correct answer and explanation is:
Correct Answers:
- Probability of gray offspring: 50%
- Probability of albino offspring: 50%
- Phenotypes of the parents:
- Female Gg: Gray
- Male gg: Albino
Explanation (300 words):
In this genetic cross, we are examining a monohybrid cross involving coat color in laboratory mice, where gray (G) is dominant over albino (g). This means that only one copy of the dominant allele (G) is needed for the mouse to appear gray. The recessive phenotype, albino, only appears when both alleles are homozygous recessive (gg).
Genotypes of Parents:
- Female (Gg): This female carries one dominant gray allele and one recessive albino allele. Because of the presence of the dominant G allele, she expresses the gray phenotype.
- Male (gg): This male carries two recessive alleles, so he expresses the albino phenotype.
Punnett Square Analysis:
| g (from male) | g (from male) | |
|---|---|---|
| G (from female) | Gg (gray) | Gg (gray) |
| g (from female) | gg (albino) | gg (albino) |
From the cross:
- 2 out of 4 offspring are Gg (gray)
- 2 out of 4 offspring are gg (albino)
Thus, the probabilities are:
- Gray offspring (Gg): 2 out of 4 = 50%
- Albino offspring (gg): 2 out of 4 = 50%
Conclusion:
This genetic cross demonstrates Mendelian inheritance with a 1:1 ratio of dominant to recessive phenotypes in the offspring. The gray coat color is dominant, so only one G allele is needed to produce a gray mouse. The appearance of both gray and albino mice in equal proportion shows how recessive traits can reappear even when only one parent is visibly expressing them.