inflammation and the transient expression of the recombinant genes. Adeno-
associated viruses are unique among animal viruses, because they require
coinfection with an unrelated helper virus (either adenovirus or herpesvirus) for
productive infection in cell culture. However, AAV has the ability to integrate
into the host genome in the absence of a helper virus, but because it integrates
at a specific location, the risk of virus-induced mutagenesis and oncogenesis is
reduced. Liposomes, however, are synthetic lipid bilayers forming spherical
vesicles, with size ranging from 25 nm to 1 mm in diameter depending on how
they are made. Liposomes can transfect a variety of cell types, are biodegrad-
able and hypoimmunogenic, and can be manufactured to a drug standard.
Theoretically, there is no restriction on the size of the DNA to be delivered by
liposome. The disadvantages are short-term expression of the transferred gene,
no specific targeting ability, and a low transfection rate in vivo.
C O M P R E H E N SIO N Q U E ST IO N S
A 30-month-old female child whose growth rate has been in the lower
10th percentile over the last year presents with chronic, nonproductive
cough and diarrhea with foul-smelling stools. She is diagnosed as hav-
ing cystic fibrosis. For which of the following vitamins is this child
most likely to be at risk of deficiency?
A. Ascorbic acid (vitamin C)
C. Folic acid
D. Retinol (vitamin A)
E. Riboflavin (vitamin B2)
Some forms of genetic diseases such as cystic fibrosis and sickle cell
anemia can be diagnosed by detecting restriction fragment length poly-
morphisms (RFLPs). Which of the following is most likely to be used
in an RFLP analysis?
B. Mass spectrometry
C. Northern blot
D. Southern blot
E. Western blot
Your patient has been diagnosed with cystic fibrosis and has been
determined to have the most common mutation, the AF508 gene. Which
of the following is the most cost- and time-effective method for testing
family members to see who are carriers of the mutation?
A. Allele-specific oligonucleotide probe analysis
B. DNA fingerprinting analysis
C. DNA sequencing
D. Restriction length fragment polymorphism analysis