Question

a) Are recessive alleles always more common than dominant alleles?

b) Explain why the Osteogenesis imperfecta (OI) allele is rare even though the (OI) allele is a dominant trait which means only one copy is necessary to show the disease phenotype?

Answer 1

a) The frequency of dominant or recessive alleles in a population cannot be determined just by its nature. It depends on the number of the gene copies of an allele present in a population. Neither dominant nor recessive can be said to be more common in any population without studying the genotypes of a population.

b) Osteogenesis imperfecta (OI) is a rare disease even though the allele responsible for causing this disorder is dominant because the frequency of this allele in the worldwide population is quite low. It is transmitted from the parent to their offspring. So, if a parent even has this allele, there is a 50% chance of transmitting it to the future generation. But the laready few copies of this allele makes OI rare.