Due to divergent evolution, some species may have similar anatomical structures with the same purposes. The species while not exactly similar are close enough to allow the interbreeding of the two, such as the horse and mule
Answer:
D. If all of the offspring are short-tailed, the unknown individual is the homozygous dominant genotype.
Explanation:
The short tail phenotype is completely dominant over the long tail phenotype. When a short tailed salamander with unknown genotype is crossed with a homozygous recessive long tailed salamander, the cross is called testcross. Lets assume that the allele "S" gives "short tail" phenotype while the allele "s" gives "long tail" phenotype.
If the "short tailed salamander" with unknown genotype is homozygous dominant (SS), the process of the testcross will express only dominant trait (cross 1). On the other hand, if the "short tailed salamander" with unknown genotype is heterozygous dominant (Ss), segregation of alleles during gamete formation would form two types of gametes (cross 2). The 50% progeny would express the "long tail" phenotype while rest 50% will express the "short tail" phenotype.
Answer;
The correct answer would be Rr.
In a monohybrid cross, the phenotype ratio of 3:1 is obtained only when both the parents are heterozygous for the trait.
In this condition, the heterozygous genotype would be Rr. The phenotype of both the parents would be round seeds (R) as the round is a dominant trait.
The cross of these parents would produce offspring with three types of genotypes RR, Rr, and rr in ratio 1:2:1.
Thus, the phenotypic ratio would come out to be 3 (round seed):1 (wrinkled seed).