Question

BACs and YACs are
(a)Natural DNA obtained from bacteria and yeast
(b)Useful vectors for eukaryotic gene transfer
(c)Artificial DNA obtained from bacteria and yeast
(d)Both B and C

Answer 1

Hint: Bacterial cells like in E. coli are used for DNA cloning with the help of BAC which is an engineered DNA molecule. Yeast cells are used for DNA cloning with the help of YAC which is an engineered DNA molecule.

Complete answer:
Bacterial Artificial Chromosome (BAC) has cloning sites, promoters, and several G+C restriction enzyme sites. Segments of an organism's DNA can be inserted into BACs that range from 100 to about 300 thousand base pairs. The inserted gene of interest of DNA in BACs is taken by bacterial cells. The bacterial cells amplify DNA as they grow and divide that are then isolated and used in sequencing DNA. The cloned DNA is in a purified form as the BAC is much tinier than the bacterial chromosome so the DNA is purified away from the rest of the bacterial cell's DNA. They are extremely useful for mapping and sequencing mammalian genes because of such features of BACs.
Yeast Artificial Chromosome (YAC) carries ARS (autonomous replication sequence), CEN (centromere), and a selectable marker which is one in each arm. It is used in the budding yeast Saccharomyces cerevisiae for cloning. Both YAC and BAC are useful for the construction of genome libraries and in gene transfer with a high degree of stability.
So, the correct answer is ‘Both B and C’.

Note: PCR is another way to make many copies of a specific region in vitro (in a test tube rather than an organism). PCR is a technique to amplify the gene of interest is usually three steps and they are denaturation, annealing, and polymerization. If the reaction is efficient, the target region can go from just one or a few copies to millions. The polymer chain reaction is also used for constructing RAPD maps which require only one primer for multiplying and detecting the presence of the transgene in an organism.