What does YAC mean in HUMAN GENOME

YAC stands for Yeast Artificial Chromosome. It is a type of genetic engineering technique designed to transfer large pieces of DNA into yeast cells. This technique was developed in the late 1980s and has since become an important tool for manipulating large pieces of DNA that are too large for other methods such as PCR or restriction enzyme digestion. YACs provide an efficient means to study complex genes, such as those involved in diseases and genetic disorders.

YACs can be used to clone, sequence, modify, and identify large pieces of DNA that may contain multiple genes or regulatory elements. They can also be used to introduce foreign genes into yeast cells and express them at high levels. This makes it possible to study the function of the gene product or test therapeutic strategies before transferring them into mammalian cells or animals models.

YACs are capable of cloning any type of DNA, including promoter regions, transcription factors, drug target sequences, metabolic pathways, genomic regions associated with diseases, and transposable elements (TEs). Due to their size and flexibility, they are especially useful for cloning difficult-to-manipulate genomic regions that contain multiple genes or TE clusters.

The process begins when a piece of DNA is inserted into a circular plasmid vector containing specific markers such as telomeric repeats at both ends and selection markers for integration into the host cell’s genome. After uptake into yeast cells by conjugation or electroporation techniques, resulting transformants are then grown in selective media. The plasmid vector integrants can then be identified using molecular probes specific for the marker sequences contained within the vector.

The main advantage offered by YAC compared to other methodologies is its ability to clone very large pieces of DNA with relative ease and efficiency - up to several hundred kilobases! Additionally, because there is no requirement for linearity when constructing artificial chromosomes it is possible to produce more recombinogenic structures like rings which can further enhance expression levels without generating sticky ends on ligation steps like in conventional cloning techniques. Finally, since several copies of each artificial chromosome may exist in a cell at any one time it facilitates easier identification by flow cytometry than most restriction-based cloning systems do.

One potential drawback associated with using a YAC system is its low transformation efficiency compared to some alternative methods such as PCR-mediated cloning techniques which typically have transformation efficiencies up in the thousands per μg range whereas YAC transformation rates are usually much lower than this (depending on organism). Secondly the endpoints produced through this system often require extensive post-transformation screening steps which limit overall throughput speed/efficiency compared with some alternative methodologies where endpoints appear quicker after ligation.

Holding times generally vary depending on individual projects but typically they range between days 1-3 weeks depending on factors such as cell culture conditions (temperature/media composition) selected marker(s) etc.. Additionally stability over multiple passages may also vary based on these same parameters so careful monitoring during propagation should always occur when dealing with larger constructs like artificial chromosomes if optimal performance is desired downstream applications.