A flowering plant with orange petals is self-crossed to yield the following phenotypes:
red flowers- 30
orange flowers- 62
yellow flowers- 33
Choose symbols and designate the genotypes of each of the above phenotypes.
I am pretty sure that the above data suggests incomplete dominance (which would yield a 1:2:1 phenotypic ratio). But how do you know which (yellow or red) is dominant? There is in example in our book of a flowering plant where red is dominant over white, so the genotypes/phenotypes would be:
WW- red
Ww - pink
ww - white
But I'm not sure which color is dominant in this cross. How do you know?
To determine which color is dominant in the self-cross of the flowering plant with orange petals, you can use the observed phenotypic ratio and the principles of Mendelian genetics.
Since the phenotypic ratio is 30:62:33 for red, orange, and yellow flowers respectively, we can assign symbols to represent the alleles for each color. Let's use the following symbols:
- R represents the allele for red flowers
- O represents the allele for orange flowers
- Y represents the allele for yellow flowers
Now, let's designate the genotypes for each of the observed phenotypes based on the provided ratios:
- Red flowers (30): The ratio for red flowers to orange flowers is 30:62, which is approximately 1:2. This suggests that red flowers are likely the homozygous recessive (rr) genotype. Therefore, we can say that the genotype for red flowers is rr.
- Orange flowers (62): The ratio for orange flowers to red flowers is 62:30, which is approximately 2:1. This indicates that orange flowers are likely the heterozygous (RO) genotype, where R represents the dominant allele and O represents the recessive allele. So, the genotype for orange flowers is RO.
- Yellow flowers (33): Since yellow flowers have a different phenotype compared to both red and orange flowers, it is likely that yellow flowers carry a different allele. However, without additional information, we cannot definitively determine the exact genotype or allele symbol for yellow flowers.
In summary, based on the observed phenotypic ratio, we can conclude that red flowers have the homozygous recessive genotype (rr) and orange flowers have the heterozygous genotype (RO). However, the exact genotype and allele symbol for yellow flowers cannot be determined without further information.