18√3-9π

18-3π

9√3-9π/2

18√3-3π

4

5

6

7

DNA that encodes specific protein

RNA

codon

allele

To speed up old-fashioned breeding methods.

To identify all the genes in the pine tree's genome.

To find out what desired traits the pine trees have.

To make it easier to know which gene needs altering.

Short-lived nature – Before gene therapy can become a permanent cure for a condition, the therapeutic DNA introduced into target cells must remain functional & the cells containing the therapeutic DNA must be stable. Problems with integrating therapeutic DNA into the genome & the rapidly dividing nature of many cells prevent it from achieving long-term benefits. Patients require multiple treatments.

Immune response – Any time a foreign object is introduced into human tissues, the immune system is stimulated to attack the invader. Stimulating the immune system in a way that reduces gene therapy effectiveness is possible.

Multigene disorders – Some commonly occurring disorders, such as heart disease, high blood pressure, Alzheimer's disease, arthritis, & diabetes, are affected by variations in multiple genes, which complicate gene therapy.

Some therapies may breach the Weismann barrier (between soma and germ-line) protecting the testes, potentially modifying the germline, falling afoul of regulations in countries that prohibit the latter practice.

0-6个月

6个月-1.5岁

1.5岁-4岁

4岁-8岁

A gene products

A + B gene products

B + C gene products

C gene products

A + C gene products