Final answer:
The cross between a grey fur dog (Gg) and a black fur dog (gg) result in one genotype of Gg (grey fur) and three genotypes of gg (black fur), following a 3:1 ratio for black to grey fur in the offspring, given the assumed complete dominance of the 'G' allele.
Step-by-step explanation:
The student's question involves predicting the genotypes and phenotypes of the offspring from a cross between two dogs with different fur colors using a Punnett square. A grey fur dog has a genotype of Gg, and a black fur dog has a genotype of gg. In the Punnett square, we place Gg on one side (G on one line, g on the next), and gg on the other side (g on both lines). After filling out the Punnett square, we find the following combinations:
- Gg (Grey fur dog)
- gg (Black fur dog)
- gg (Black fur dog)
- gg (Black fur dog)
Therefore, the possible genotypes and phenotypes of the offspring are:
Genotype Gg: 1 in 4 chance, Phenotype Grey fur.
Genotype gg: 3 in 4 chance, Phenotype Black fur.
In this case, we are assuming complete dominance, where 'G' is dominant over 'g', determining grey fur over black fur. Therefore, we have a 3:1 ratio of black to grey fur in the offspring.