Question

in roses, red flowers and long stems are dominant traits. a rose plant that is homozygous for both red flowers and long stems is crossed with a rose plant that is heterozygous for red flowers and homozygous for short stems. what percentage of the offspring will exhibit red, long - stemmed flowers? 25 percent 50 percent 75 percent 100 percent

Explanation:

Step1: Define alleles

Let \(R\) represent the allele for red flowers (dominant) and \(r\) for non - red flowers, and \(L\) for long stems (dominant) and \(l\) for short stems. The homozygous red - flowered and long - stemmed plant has genotype \(RRLL\), and the heterozygous red - flowered and homozygous short - stemmed plant has genotype \(Rrll\).

Step2: Determine gametes

The \(RRLL\) plant can only produce gametes with \(RL\). The \(Rrll\) plant can produce two types of gametes: \(Rl\) and \(rl\) in a 1:1 ratio.

Step3: Use Punnett - square or probability rules

When we cross them, using the multiplication rule of independent events in genetics. The probability of getting a red - flowered offspring (\(R -\)) is 1 (since all offspring will get at least one \(R\) allele from the \(RR\) parent). The probability of getting a long - stemmed offspring (\(L -\)) is 0.5 (because half of the gametes from the \(Rrll\) parent have the \(l\) allele). The probability of getting red and long - stemmed offspring is \(1\times0.5 = 0.5\) or 50 percent.

Answer:

50 percent