Question

please help!!

Read the passage below taken from the National Library of Medicine website: Oculocutaneous albinism is caused by the inability to produce a pigment called melanin, which is the substance that gives skin, hair, and eyes their color. In the retina, melanin also plays a role in normal vision. Individuals with oculocutaneous albinism have reduced pigmentation in the skin, hair, and eyes and also have vision problems. A homozygous mutation in the OCA2 or TRP1 gene leads to oculocutaneous albinism. Alterations in the MC1R gene can change the appearance of people with oculocutaneous albinism. This gene helps regulate melanin production and is responsible for some normal variation in pigmentation. People with genetic changes in both the OCA2 and MC1R genes have many of the usual features of oculocutaneous albinism, including light-colored eyes and vision problems; however, they typically have red hair instead of the usual blond hair seen with this condition. How many of the following concepts are described in the passage? polygenic trait • gene interactions • codominance . multiple common alleles (polymorphism) pleiotrophy

This is all the informarjon I have.

Answer 1

Ans:

Polygenic trait: Polygenic Trait is one whose phenotype is influenced by more than one gene. Now as given in the question that a homozygous mutation in OCA2 or TRP1 gene leads to the disease this means that both of these genes are responsible for the normal trait. So the trait is a polygenic trait.

Gene Interaction: Gene interactions occur when two or more allelic or non-allelic genes of same genotype influence the outcome of particular phenotypic character. Now as given in the question that MC1R gene helps regulate melanin production so this gene is interacting with the gene producing melanin and regulate the production of melanin. Also mutation in both OCA2 and MC1R gene leads to the usual features of the disease. So gene interaction is taking place here.

Codominance: When two alleles for a trait are equally expressed with neither being recessive or dominant, it creates codominance. Now as given in the question that a homozygous mutation leads to the disorder that means one allele is dominant and one is recessive and if one of the dominant allele is present than it will leads to the normal product. So codominance concept is not applicable here.

Polymorphism: It is a discontinuous genetic variation resulting in the occurrence of several different forms or types of individuals among the members of a single species. A discontinuous genetic variation divides the individuals of a population into two or more sharply distinct forms. Now this albinism is dividing individuals into distinct forms like individuals suffering from this disorder, individuals having major features of this disease and individuals normal for this disorder so we can say that this trait is showing polymorphism.

Gene Pleioptropy: Gene pleiotropy occurs when a gene product interacts with multiple other proteins or catalyzes multiple reactions. Albinism is an example of pleiotropy as given in the question that genes participating in melanin production are also interacting with other genes for melanin regulation and for the formation of final phenotypic effect.

So From all the five characteristics this trait is showing 4 characteristics.