Using the genomic libraries in Problem 4, you wish to clone the human gene encoding myostatin, which is expressed only in muscle cells.How frequently will a clone representing myostatin be found in the genomic library made from brain?

Verified step by step guidance

1. Step 1: Understand the problem. The goal is to determine the frequency of finding a clone representing the myostatin gene in a genomic library made from brain cells. Myostatin is expressed only in muscle cells, so its mRNA is not present in brain cells.
2. Step 2: Recall the difference between genomic libraries and cDNA libraries. A genomic library contains DNA fragments representing the entire genome, including both coding and non-coding regions, regardless of whether the genes are expressed in a specific tissue. A cDNA library, on the other hand, is made from mRNA and represents only the genes expressed in the tissue used to create the library.
3. Step 3: Note that the genomic library made from brain cells will contain the entire genome of the organism, including the myostatin gene, even though myostatin is not expressed in brain cells. This is because genomic libraries are not dependent on gene expression.
4. Step 4: Calculate the frequency of finding the myostatin gene in the genomic library. To do this, divide the size of the genome by the average size of the DNA fragments in the library. The formula is: \( \text{Frequency} = \frac{1}{\text{Number of clones in the library}} \), where the number of clones is determined by \( \text{Number of clones} = \frac{\text{Genome size}}{\text{Average fragment size}} \).
5. Step 5: Substitute the values for genome size and average fragment size into the formula. Ensure that the units are consistent (e.g., base pairs or kilobase pairs). This will give the frequency of finding a clone representing the myostatin gene in the genomic library made from brain cells.

Key Concepts

Genomic Libraries

Genomic libraries are collections of DNA fragments that represent the entire genome of an organism. These libraries are created by cloning DNA into vectors, allowing researchers to isolate and study specific genes. The composition of a genomic library can vary depending on the tissue source from which the DNA is extracted, influencing the presence of specific genes, such as myostatin, which is primarily expressed in muscle cells.

Gene Expression

Gene expression refers to the process by which information from a gene is used to synthesize functional gene products, typically proteins. Different genes are expressed in different tissues, meaning that a gene like myostatin, which is specifically expressed in muscle cells, may not be present in significant amounts in a genomic library derived from brain tissue. This differential expression is crucial for understanding the likelihood of finding specific genes in various genomic libraries.

Cloning and Selection

Cloning in genetics involves creating copies of a specific DNA segment, often using vectors to introduce the DNA into host cells. When constructing a genomic library, the selection of clones is based on the presence of specific genes. In the case of myostatin, if the genomic library is derived from brain tissue, the likelihood of finding a clone representing this muscle-specific gene is low, as it is not typically expressed in that tissue.