4. In roses, long stem is dominant over short stems. A Homozygous long-stemmed plant is crossed
with a homozygous short-stemmed plant. What percentage of the resultant rose plants will have long stems?

100%

Explanation:

This question involves a single gene coding for stem length in the rose plant. The allele for long stem (L) is dominant over the allele for short stem (l). This means that allele L will mask the phenotypic expression of allele l in a heterozygous state.

According to the question, a homozygous long-stemmed rose i.e. a rose plant that has same alleles for long stem, LL and a homozygous short-stemmed plant i.e. a rose plant that has same alleles for short stem, ll is crossed. Using a punnet square, all the F1 offsprings of this cross will have a genotype: Ll

Since (L) is dominant over (l), offsprings (Ll) will have a long-stemmed phenotype. Since all offsprings are long-stemmed, this means that 100% of the offsprings are long-stemmed.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.