Bacillus subtilis under ideal conditions occupies 5% of the total volume of a fermenter. Under such conditions; the culture medium (after bacilli are filtered off) has a concentration of 1mg/ml of the secreted protein trehalae
(i) Calculate the volume of culture filtrate required to purify 1 kg of trehalase
(ii) What are the total number of B. subtilis cells which produce this amount of enzyme? Assume that each cell is a cylinder which has dimensions of 1 m diameter and length 2μm.

What is the primary purpose of neomycin in creating mice with knockouts in gene X?

A. Neomycin selects for the survival of embryonic stem cells (ES) that have incorporated the mutant gene X anywhere in the genome

B. Neomycin selects for the survival of ES cell that have incorporated the mutant gene in the place of the wild-type gene

C. Neomycin prevents Candida infection during ES cell culture that does not have gene X

D. Neomycin makes the gene X knock-out mice resistant to Candida infection

The growth medium for mammalian cells contains serum. One of the major functions of serum is to stimulate cell growth and attachment. However, it must be filter sterilized to

A. Remove large proteins

B. Remove collagen only

C. Remove mycoplasma and microorganisms

D. Remove foaming agents

During the media preparation for cultivation of cells, insoluble precipitates of calcium phosphates are often formed, identify which method can be adopted to avoid this problem?

A. Hold the pH at 5.6

B. Hold the pH at 7.5

C. Add calcium salt first and then phosphate source

D. None of the above

To create a transgenic organism:

A. Introduce foreign DNA into a gamete or fertilized ovum

B. Inject a gene of interest into a somatic cell

C. Inject a gene of interest into several somatic cells

D. Introduce foreign DNA into somatic cells in culture and transplant them