What is the difference between genome, genomic library, cDNA library?

The genome is the entire DNA information in a cell of an organism.

These DNA are interrupted, attached to a vector and transferred to microorganisms so that these microbial cells contain the entire genome of an organism. These microorganisms then make up the genome library.

Both of the above contain genetic information. The genetic information of any cell is the same for a certain organism.

cDNA is obtained by reverse transcription of intracellular mRNA, which contains an intracellular expression information. The expression information of different cells in multicellular organisms is often different. If all of the mRNA (also known as the cell's transcriptome) of a cell is reverse transcribed into cDNA, and then these cDNA are attached to a vector (basically uninterrupted) and transferred into microorganisms, then these microorganisms form a cDNA library.

In simple terms, genomes are molecules, genomic libraries are microorganisms that represent genetic information, and cDNA libraries are microorganisms that represent information.

The different construction methods and purposes of the two types of libraries determine the difficulty of isolating and extracting genes.

Some genes in genomic libraries (especially non-digested fractions that cannot be expressed to form mRNA) are difficult to isolate from genomic libraries by some method, affecting their potential for interspecies communication.

There are no introns, promoters, and terminators in the genes of cDNA. In genetic engineering, if a prokaryotic organism is used as a recipient cell, the target gene is a gene from the eukaryotic genome library, and the gene of the eukaryotic genome library contains introns, and there is no intron shearing enzyme in the prokaryotic organism, it will not work, and if the target gene is from the gene of the eukaryotic cDNA library, its gene does not have introns, it can be used.

A gene bank is a virtual concept. Refers to all genes of all individuals in a population.

A gene bank is a group of microorganisms that store genes for a species. For example, we can cut all human genes with restriction enzymes, connect these gene fragments with DNA ligase, introduce them into bacterial cells, and then culture these bacterial cells in large quantities to form a gene library. These gene libraries contain all kinds of genes of a species, also known as genomic libraries.

So, gene libraries include genomic libraries.