Studies have suggested (although not proved) that whether you are right- or left
ID: 176772 • Letter: S
Question
Studies have suggested (although not proved) that whether you are right- or left-handed may be hereditary. Homozygous-dominant (RR) people are strongly right- handed and are not easily influenced to change preferences. Homozygous-recessive individuals are strongly left-handed. Heterozygous individuals are more variable. They are potentially ambidextrous but are easily influenced by environment training. Would you characterize handedness as an example of complete dominance, incomplete dominance, or codominance? Would it be possible for a left-handed person to be heterozygous? Would it be possible for two left-handed parents to have a right-handed child? Explain. For this problem, assume that one allele is completely dominant over the other. Suppose two individuals heterozygous for a single trait have children. What is the expected phenotypic ratio of the offspring? If two individuals heterozygous for two traits have children, what would be the expected phenotypic ratio of the offspring? Remember that the gene for each trait is located at a locus, a physical region the chromosome. Suppose that crossing two individuals heterozygous for two traits resulted in the same phenotypic ratio as for a single trait. Are the genes for these two traits on separate chromosomes or on the same chromosome? Explain your answer.Explanation / Answer
1. Handedness is an example of complete dominance. It is a type of inheritance in which the dominat allele completely masks the effect of recessive allele in heterozygous condition. In this case, the heterozygous genotype would be Rr, where the dominant gene masks the recessive and the phenotype would be right handed indiviual.
2. No, it is not possible for a left handed person to be heterozygous. This is because if the trait is heterozygous, the dominant trait always takes over. In this case it would be Rr where the R (Right handedness) is dominant and so the trait will be right handedness.
3. No, this is not possible. Both left handed parents would have a genotype of rr, having no dominat traits at all. If they were to mate, it would be rrrr, still no dominant traits , making it impossible for them to have right handed children.