Problem 9 - Biology: The Unity and Diversity of Life

Question

A gene that is knocked out is ________ a. deleted b. inactivated c. expressed d. either a or b

Step-by-Step Solution

Answer

The correct answer is d. either a or b.

Step 1: Understand 'Knocked Out' Definition

The term 'knocked out' in genetics refers to a gene that has been rendered non-functional. This means the gene has either been deleted from the genome or altered in such a way that it no longer produces a functional product.

Step 2: Evaluate Option A 'Deleted'

If a gene is 'deleted,' it is completely removed from the genome. A deleted gene is definitely considered 'knocked out,' as it can no longer express any functional product.

Step 3: Evaluate Option B 'Inactivated'

An inactivated gene is still present in the genome but has been altered so that it no longer produces a functional product. This is another form of 'knocking out' a gene, as it achieves the same end result - preventing gene expression.

Step 4: Evaluate Option C 'Expressed'

A gene that is 'expressed' is active; it produces RNA and possibly a protein product. This is the opposite of being 'knocked out.' Thus, an expressed gene cannot be considered as knocked out.

Step 5: Evaluate Option D 'Either A or B'

Since both 'deleted' and 'inactivated' accurately describe a knocked-out gene, this option is correct. A knocked-out gene can either be not present (deleted) or present but not functional (inactivated).

Key Concepts

Gene Deletion

Gene deletion refers to the complete removal of a gene from an organism's genome. This process ensures the gene is no longer present to perform any function. In genetic research and experiments, gene deletion is a valuable tool to study the effects of a missing gene, as it allows researchers to observe what happens when a particular gene is absent.
One common method of gene deletion involves using CRISPR-Cas9 technology, where specific DNA sequences are targeted and removed. This method is both precise and efficient, enabling researchers to achieve their desired genetic alterations.
Gene deletion is a crucial strategy in understanding various genetic disorders and developing treatments. By observing how a gene's absence affects an organism, scientists can learn about a gene's role and function in growth, development, and overall health.

Gene Inactivation

Gene inactivation occurs when a gene is present in the genome but is altered or regulated so that it no longer produces a functional product. This means the gene's expression is either reduced or completely stopped, even though the genetic sequence remains intact.
There are several methods to achieve gene inactivation:

• RNA interference (RNAi): This technique uses small RNA molecules to interfere with gene expression by degrading the gene's messenger RNA (mRNA).
• Mutagenesis: This involves introducing mutations that either disrupt the gene’s normal coding sequence or affect regulatory regions controlling gene expression.
• Epigenetic modifications: These are changes to the genome that do not alter the DNA sequence but affect gene expression. Examples include DNA methylation and histone modification.

Gene inactivation is important in research for creating model organisms to study diseases or develop new therapeutic approaches without permanently altering the organism's genetic framework.

Gene Expression

Gene expression is the process through which genetic information from a gene is used to synthesize proteins and other molecules that perform vital functions in cells. This process involves two main steps: transcription and translation.

• Transcription: In this step, the DNA sequence of a gene is copied into messenger RNA (mRNA). This happens in the cell's nucleus where the DNA resides.
• Translation: The mRNA is then used as a template to build proteins. Ribosomes, cellular structures responsible for protein synthesis, read the mRNA sequence and assemble the corresponding amino acids to form a protein.

Gene expression is tightly regulated and can be influenced by various factors such as environmental conditions, developmental stages, and cellular needs. This regulation ensures that genes are expressed at the right time, in the right cell type, and in the appropriate amount, which is critical for maintaining proper cellular function and overall organismal health.