1. The gene responsible for the pea color phenotype is SGR gene or “stay green” gene. This gene encodes for the protein responsible for the chlorophyll degradation. So, when there is a mutation in this gene, and the gene product is not functional, the chlorophyll stays around and the pea is green.
2. The correct answer is: y, the recessive allele.
Null allele is usually a consequence of a mutation. It is a nonfunctional copy of a gene that “destroys” the function of the gene. Recessive allele can be compared to null allele in term that it shows no effect when is in heterozygous (only dominant is expressed).
3. When it comes to SGR gene (gene for the pea color): Allele Y is dominant over y because in heterozygous (Yy) the gene SGR still encodes for the protein product, which degrades chlorophyll (in recessive homozygous there is no protein product). So, consequently the phenotype of the plant is not green, the color of the plant is yellow.
4. The gene responsible for the pea color phenotype is SGR gene or “stay green” gene. This gene encodes for the protein responsible for the chlorophyll degradation. There are two alleles of this gene, Y dominant and y recessive one. So, when there is a mutation in this gene (both alleles are recessive-yy), the gene product is not functional, the chlorophyll stays around and the pea is green. But, when there is even one dominant allele Y, the product functions properly, and the pea plant is yellow.
5. The amount of protein produced from a gene is roughly proportional to the number of functional copies of the gene means that, there is more gene product (protein for chlorophyll degradation) in YY than in Yy genotype. This is because there are two functional copies in dominant homozygous(YY), only one in heterozygous (Yy) and none functional copy in recessive homozygous (yy-there is no protein product).
