Final answer:
Tail length in mice with given heritability values is primarily determined by genetics. A dihybrid cross reflects the independent assortment and results in specific phenotypic ratios. The Punnett square is a tool used to predict these ratios, such as 1:1 for a cross between a white-eyed male and a heterozygous red-eyed female fruit fly.
Step-by-step explanation:
When considering if a cross between a mouse with a long tail and a mouse with a short tail would result in progeny with intermediate tail lengths, you have to consider the heritability of the trait. Since you have provided the heritability figures (VE = 15 VA = 175 VD = 10 VI = 5), we can conclude that tail length in these mice is largely determined by genetic factors, with a high heritability (VA) compared to environmental variance (VE). Thus, if tail length follows a simple Mendelian pattern of inheritance, the offspring will exhibit the dominant phenotype, rather than an intermediate form. If long tail is dominant over short tail, all F1 progeny will have long tails. However, in the F2 generation resulting from the mating of F1 individuals, there may be a variety in tail lengths according to a 3:1 Mendelian ratio, if long is dominant, or a 1:2:1 ratio if incomplete dominance is in play.
Regarding the dihybrid cross, a phenotype ratio of 9:3:3:1 in the F2 generation indicates the independent assortment of two traits, as seen in Mendelian genetics. This example involves two traits: coat color and tail length, with brown (B) being dominant over white (b) and short tail (S) being dominant over long (S) in mice.
The Punnett square analysis of crosses in genetics problems helps us predict the expected phenotypic ratios. For instance, crossing a white-eyed male fruit fly with a female that is heterozygous for red eye color will result in a 1:1 phenotypic ratio of red-eyed to white-eyed offspring. If we cross a dwarf pea plant (homozygous recessive) with a tall pea plant (heterozygous), we would get a phenotypic ratio of 1:1 for tall to dwarf pea plants. These principles help us understand the expected outcomes in genetic crosses, assuming independent assortment and no linkage between genes.