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. Understand that a genomic library contains DNA fragments representing the entire genome of an organism, regardless of the tissue from which it was derived.
2. Recognize that myostatin is a gene expressed specifically in muscle cells, but its DNA sequence is present in all cells, including brain cells, because all cells contain the entire genome.
3. Consider that the genomic library made from brain cells will have DNA fragments that include the myostatin gene, even though it is not expressed in brain cells.
4. Estimate the frequency of finding a specific gene in a genomic library by considering the size of the genome and the average size of the DNA fragments in the library.
5. Calculate the probability of finding the myostatin gene in a clone by dividing the size of the human genome by the average size of the DNA fragments in the library, which gives the number of clones needed to represent the entire genome.

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 based on the tissue source, as different tissues express different sets of genes.

Gene Expression and Tissue Specificity

Gene expression refers to the process by which information from a gene is used to synthesize functional gene products, typically proteins. Tissue specificity indicates that certain genes, like myostatin, are expressed predominantly in specific tissues, such as muscle cells. This means that a genomic library derived from a non-expressing tissue, like the brain, is less likely to contain clones of genes that are not expressed in that tissue.

Cloning and Screening

Cloning involves inserting a DNA fragment into a vector to replicate it within a host organism, often bacteria. Screening is the process of identifying clones that contain the desired DNA sequence. In the context of a genomic library from the brain, the likelihood of finding a clone for myostatin is low, as the gene is not expressed in brain tissue, leading to fewer or no clones representing it.