Final answer:
When two heterozygous Netherlands dwarf rabbits mate, the expected proportion of surviving offspring that are dwarfs is 2 out of 3, or approximately 66.7%. This calculation takes into account the recessive lethal nature of the genotype homozygous for the other allele, resulting in only the dwarf and small rabbit phenotypes among surviving offspring.
Step-by-step explanation:
In the scenario with the Netherlands dwarf rabbits, we are dealing with a gene that exhibits incomplete dominance and produces three phenotypes. The two dwarf rabbits, which are heterozygous, would be represented by Dd (with D representing the dwarf allele and d representing the allele for smaller size). We're given that rabbits homozygous for the other allele are deformed and die, which suggests a recessive lethal pattern for homozygous individuals (dd).
When two heterozygous individuals (Dd) mate, the expected genotypic ratio from a Punnett square is 1:2:1; however, considering the lethal nature of the dd genotype, we will only see the surviving genotypes. The expected ratio of surviving offspring, therefore, becomes 1 D (homozygous for the dwarf allele, resulting in a small rabbit) to 2 Dd (heterozygous, resulting in dwarf rabbits). Thus, for every three surviving offspring, two would be expected to be dwarf rabbits.
The proportion of surviving offspring that should be dwarf rabbits is therefore 2 out of 3, or approximately 66.7% (assuming a large enough sample size for the ratios to approach expected values). It is important to note that the recessive lethal allele has a huge impact on the outcome of such crosses, and this reflects a more complex pattern than simple Mendelian inheritance.