Question

Commonly used vectors for human genome sequencing are
A) T DNA
B) BAC and YAC
C) Expression vectors
D) T/A cloning g vectors

Answer 1

Hint:Expression and cloning functions are not necessary for genome sequencing. Their role is more important for the insertion of foreign DNA into another cell for procedures like antibiotic production.

Complete answer:
Currently, the most commonly used vectors are BAC or bacterial artificial chromosome. These have been created from F-plasmids which are involved in bacterial conjugation, and can carry up to 300 kbp of foreign, inserted DNA. Yeast artificial chromosomes or YACs can carry even more, up to 1000 kbp. Yeast Artificial Chromosomes have in fact been around for much longer than Bacterial Artificial chromosomes. However, While YAC can be used for cloning and sequencing, BACs are much more stable.

An expression vector’s role is more for the production of a particular gene product. Synthesis of mRNA and it’s translation into protein off the vector is the main outcome desired. Cloning vectors are used to create large copies of a particular gene or stretch of DNA. Unlike more traditional vectors, T/A cloning does not use restriction endonucleases which create sticky ends, but Taq polymerase instead by which 3’ extensions of thymine are added to the ends. This can be done very easily using PCR techniques. T-DNA itself is a section of the Ti plasmid of Agrobacterium.

Hence the correct answer is option ‘B’

Note:As BACs get their ori or origin of replication from the E. coli F plasmid, they have the advantage of easily being maintained in just one copy per cell. This makes it even easier to maintain the vector.