Question

A geneticist wants to identify genes that may be involved in resistance to COVID-19 infection. While you cannot perform mutational screens in humans, (you could - but it's highly unethical and illegal) you can perform these in human tissue culture. The experiment is designed to screen for cells that gain the ability to resist infection after being treated with a mutagen. This approach would be considered a:

	a.	None of these answers are correct
	b.	reverse genetic screen
	c.	pleiotropic screen
	d.	forward genetic screen
	e.	autosomal screen
	f.	heterozygous screen

Answer 1

The right option is (d) forward genetic screen

Explanation:

Reverse genetic screen: – (gene -> mutant phenotype) In reverse genetic screen we have already known genotype (gene) but not know their phenotype. In order to find out the phenotype of a particular gene, we disrupt that gene and analysis the outcome phenotype. [ Option (b) is wrong because in question the trait ( ability to resistant infection) already known and have to find out gene]

Pleiotropic screen: A gene that exhibits multiple phenotypic expressions. In the pleiotropic screen, we try to find out a gene that has an influence on two or more unrelated phenotypic traits. [ therefore option (c) is wrong]

Forward genetic screen: – (mutant phenotype -> gene) Typically mutant phenotypes are known and their corresponding genes have been identified. In this organism is treated with a mutagen, then screen phenotypes of interest. [ In question, we have already known mutant phenotype (resistant to infection) and gene have been identified therefore Option (d) is right ]

Autosomal screen: To screen autosomal linked gene/trait. [Option (e) is wrong]

Heterozygous screen: to screen heterozygous genotype of a particular phenotype. [ Option (f) is wrong]