Final answer:
The gey-2 gene is involved in the expression of two phenotypes in pea plants: green or yellow pod color, and full or constricted pod form, depending on the combination of dominant and recessive alleles present.
Step-by-step explanation:
The gey-2 gene in a diploid organism is responsible for determining two specific phenotypes related to the physical characteristics associated with seed pod color and form in pea plants, based on Mendelian genetics. In such plants, two alleles for the pod color gene and two for the pod shape gene can produce different combinations, resulting in observable phenotypic variations. According to the genetic information provided, the capital 'G' represents the dominant allele for green pod color, which is dominant over the 'g', the recessive allele that leads to yellow pod color. Similarly, 'F' denotes the dominant allele for full pod form, while 'f' represents the recessive allele for constricted pod form.
Using a Punnett square, which helps predict the genotypic and phenotypic outcome of crosses between plants, we can determine that a plant with the genotype 'GgFf' would be heterozygous for both traits. It would have green pods due to the dominant 'G' allele and full pods due to the dominant 'F' allele. Conversely, the homozygous recessive 'ggff' would result in a plant with yellow and constricted pods as both 'g' and 'f' traits are recessive.
Therefore, based on the genetics of pea plants, the gey-2 gene does not encode for two specific phenotypes in isolation, but rather, it can be involved in the expression of green or yellow pod color and full or constricted pod form, depending on the combination of alleles present in an organism's genotype.