Youtor
Yeast artificial chromosome YACs
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=JtWJaMCXhvI
This cloning vector lecture explains about the yeast artificial chromosome. http://shomusbiology.weebly.com/ • Download the study materials here- • http://shomusbiology.weebly.com/bio-m... • Yeast artificial chromosomes (YACs) are genetically engineered chromosomes derived from the DNA of the yeast, Saccharomyces cerevisiae, which is then ligated into a bacterial plasmid. By inserting large fragments of DNA, from 100--1000 kb, the inserted sequences can be cloned and physically mapped using a process called chromosome walking. This is the process that was initially used for the Human Genome Project, however due to stability issues, YACs were abandoned for the use of bacterial artificial chromosomes (BACs). Beginning with the initial research of the Rankin et al., Strul et al., and Hsaio et al., the inherently fragile chromosome was stabilized by discovering the necessary autonomous replication sequence (ARS);[1] a refined YAC utilizing this data was described in 1983 by Murray et al.[2] The primary components of a YAC are the ARS, centromere, and telomeres from S. cerevisiae. Additionally, selectable marker genes, such as antibiotic resistance and a visible marker. Without these sequences, the chromosome will not be stable during extracellular replication, and would not be distinguishable from colonies without the vector.[3][4] • Yeast expression vectors, such as YACs, YIps (yeast integrating plasmids), and YEps (yeast episomal plasmids), have an advantage over bacterial artificial chromosomes (BACs) in that they can be used to express eukaryotic proteins that require posttranslational modification. • However, YACs are significantly less stable than BACs, producing chimeric effects : artifacts where the sequence of the cloned DNA actually corresponds not to a single genomic region but to multiple regions. Chimerism may be due to either co-ligation of multiple genomic segments into a single YAC, or recombination of two or more YACs transformed in the same host Yeast cell.[7] The incidence of chimerism may be as high as 50%.[8] Other artifacts are deletion of segments from a cloned region, and rearrangement of genomic segments (such as inversion). In all these cases, the sequence as determined from the YAC clone is different from the original, natural sequence, leading to inconsistent results and errors in interpretation if the clone's information is relied upon. Due to these issues, the Human Genome Project ultimately abandoned the use of YACs and switched to bacterial artificial chromosomes, where the incidence of these artifacts is very low. Source of the article published in description is Wikipedia. I am sharing their material. Copyright by original content developers of Wikipedia. • Link- http://en.wikipedia.org/wiki/Main_Page
#############################
