[crimsonknight3]

Is it possible that in the future science will allow us the ability to modify our genes? If so i've always wondered how you could change the  dna of a person... In order to modify the dna would you need a complete bone marrow + blood transfusion or would it be more like a bacteria of virus that destroys and replaces your born dna with the modified dna?

[CliffordK]

I think much of the current research (in adults) is to take viruses, some of which are good at adding DNA to cells, and using them to transport new genetic material to cells.  The original genes are usually left intact.  In many cases a specific organ may be targeted. 

Genetic manipulation of an oocyte may be different.  However, it would be a daunting task to select individual genes for modification.  And, the pretty pictures of chromosomes are only made during cellular division, so adding and subtracting individual chromosomes is difficult. 

If one messes up the genetic makeup of the reproductive organs, the testes or ovaries, then future generations could be put at risk.

Bone marrow transfusions are used to treat leukemia, and are a brutal, dangerous procedure that normally involves killing one's existing bone marrow, and infusing marrow stem cells from a donor.  It can change the genetic makeup of the blood including changing one's blood type, but not of the body as a whole.

[crimsonknight3]

I see, thank you for answering!

So if you wanted to physically alter a person e.g. for changing the sex or height or hair colour etc I do know it's possible to do it before birth but would it be possible to do this after birth? Alter the genes and the person would slowly take on the new characteristics?

[CliffordK]

Some things such as height may not be dependent on every cell in the body, but rather may be dependent on hormones.  So, presumably it would be possible to target specific growth hormones with gene therapy.

Or, if a person had a deficit such as a defective pituitary gland, potentially the functions could be replaced through gene therapy.