FINAL - CH 13

Question 1

Ex vivo therapy:

Answer 1

somatic cells are removed from the patient and manipulated in the lab, then returned to the patient

Question 2

In vivo therapy:

Answer 2

somatic cells are genetically altered in the patient

Question 3

Desirable Characteristics of Somatic Cells Used for Gene Therapy

Answer 3

Cells are easily accessible

Long life span in body

Proliferating cells are preferred because the vector carrying the good version of the gene can integrate into new cells

Question 4

Different Methods of Gene Delivery

Answer 4

Viral vector deliver

Liposome fusion

Electroporation
-cell is momentarily electrically shocked to create holes in the membrane that allows DNA to enter cell

CRISPR

Question 5

Retroviral vectors

Answer 5

RNA viruses that use reverse transcriptase to make DNA copy to integrate into host chromosomes

Seldom provoke immune response

Viruses are modified to prevent replication and infection of host cells

Question 6

Disadvantages for Retroviral vectors

Answer 6

preferentially integrates into gene-rich regions of DNA, thus can insert near a proto-oncogene and activate it to cause cancer

can only infect dividing cells because it can only integrate when nuclear membrane is dissolved.

Question 7

Different Viruses used for Gene Therapy

Answer 7

can insert DNA into often inaccessible neurons

Question 8

Lentivirus

Answer 8

a type of retrovirus, but can enter non-dividing cells through pores in the nuclear membrane

ex HIV

Question 9

Challenges still facing viral gene therapy

Answer 9

Transient and low-level expression

Difficulty in reaching or specifying target tissue

Necessity for precise regulation of gene activity

Potential for insertional mutagenesis

Question 10

Transient and low-level expression

Answer 10

only some cells incorporate the virus/gene

sometimes cells methylate, thus inactivate the gene

lack of enhancer sequences may diminish expression

Question 11

Difficulty in reaching or specifying target tissue

Answer 11

e.g. neurons (harder) vs. lymphocytes (easier)

Question 12

Necessity for precise regulation of gene activity

Answer 12

some conditions require strict regulation and balance of the amount of products produced

Question 13

For these types of conditions (gain-of-function or dominant negative mutations), ________ therapies may be helpful:

Answer 13

gene blocking

Antisense therapy

Ribozyme therapy

RNA interference

Question 14

gene replacement is applicable to correct _________ mutations, it is NOT effective in correcting _________ or _________ mutations

Answer 14

loss-of-function

gain-of-function

dominant negative

Question 15

Antisense therapy

Answer 15

DNA oligonucleotide is synthesized to be complementary to the mRNA sequence produced by the gain-of-function mutation

This antisense DNA bind to the abnormal RNA and prevents is translation

Question 16

con to Antisense therapy

Answer 16

the oligonucleotide is often degraded before it can reach its target

Question 17

Ribozyme therapy

Answer 17

enzymatic RNA molecule that cuts RNA sequences

can be engineered to cut specific mRNA sequences that contain a specific mutation

Question 18

RNA interference (RNAi)

Answer 18

natural phenomenon evolved to defend cells from viral infections

lls normally use “dicer” enzyme to digest double stranded RNA which are produced by many viruses, into 20-bp pieces. These double stranded pieces separate and are used as templates to bind to and destroy single stranded RNA with the same sequence

The RISC (RNA inducing silencing complex) helps separate the 2 strands.

can artificially synthesize double stranded RNA that correspond to disease causing DNA sequences, thereby destroying the mutant mRNA products

Question 19

Although _______ is applicable to correct _________ mutations, it is NOT effective in correcting _____________ (e.g. Huntington’s, Marfan’s syndrome) because: _____________

Answer 19

gene replacement

loss-of-function

gain-of-function or dominant negative mutations

the defective gene product must be disabled in some way