23. A geneticist interested in immune function induces random mutations in a number ofspecific genes
in mice and then determines which of the resulting mutant mice have impaired immune function.
This approach is an example of:
(a) Both forward and reverse genetics,
(b) Forward genetics,
(c) Neither forward nor reverse genetics,
(d) Reverse genetics

Introduction

Genetic research has drastically advanced our understanding of how genes influence various biological functions. Two major approaches that geneticists use to study gene function are forward genetics and reverse genetics. These methods are essential for uncovering how specific genes contribute to complex biological processes such as immune function.

In this article, we will examine the differences between forward and reverse genetics, and explore how these techniques are applied in studying immune function in mice.

What is Forward Genetics?

Forward genetics is a technique where scientists start with a phenotype (observable characteristics) and work backward to identify the genetic mutations responsible for that phenotype. In forward genetics, random mutations are introduced into the genome of an organism, and the resulting phenotypic changes are then analyzed. The goal is to find the genes that contribute to the observed phenotype.

For example, if a geneticist is interested in studying immune function, they might introduce random mutations into the mouse genome and then observe which of the mutant mice have impaired immune function. By identifying the genes associated with immune function, researchers can gain insight into how specific genes affect the immune system.

What is Reverse Genetics?

Reverse genetics, on the other hand, is a technique that starts with a known gene and seeks to determine its function by studying the effects of disrupting or altering that gene. In reverse genetics, scientists begin with a specific genetic sequence and introduce mutations or deletions in order to observe how these changes affect the organism’s phenotype.

For example, a reverse genetics approach could involve knocking out a specific gene in a mouse and then examining whether the mouse’s immune function is affected. This method allows researchers to study the function of a single gene in isolation and is often used when scientists already know which genes are involved in a process but want to study their specific roles in detail.

Difference Between Forward and Reverse Genetics

The key difference between forward and reverse genetics lies in the starting point of the study:

• Forward Genetics: Starts with a phenotype (such as immune dysfunction) and works toward identifying the gene(s) responsible for the phenotype.

• Reverse Genetics: Starts with a known gene and examines the effects of altering or deleting the gene to understand its function.

The Approach in the Question: Forward or Reverse Genetics?

In the scenario described in the question, the geneticist is inducing random mutations in specific genes in mice and then determining which mice exhibit impaired immune function. Since this approach starts with a phenotype (impaired immune function) and works toward identifying the genetic mutations that cause it, this is an example of forward genetics.

By introducing random mutations and observing their effects on the immune system, the geneticist is using forward genetics to map genes responsible for immune function.

Correct Answer

Given that the geneticist is working from a phenotype (impaired immune function) to identify the underlying genetic causes, the correct answer is:

(b) Forward genetics

Conclusion

Both forward and reverse genetics are powerful tools in genetic research, each with its own unique approach to studying gene function. Forward genetics starts with phenotypes and works backward to uncover the genes responsible for specific traits, while reverse genetics starts with a gene and investigates its function through targeted mutations. Understanding the difference between these methods is crucial for interpreting genetic experiments and making meaningful discoveries about how genes influence biological processes such as immune function.

Answer:

The correct answer is:
(b) Forward genetics