Mutations that change the nucleotide sequence without changing the amino acid sequence are

Mutations that change the nucleotide sequence without changing the amino acid sequence are synonymous mutations.

Synonymous mutations or substitution are those that change a codon with another codon that codes for the same amino acid. As a result, the synthesized amino acid sequence is not modified. Synonymous mutations usually don’t result in any phenotypic effects, so they are called silent. 

advantage of using stem cells in medical research:

1.       it provides medical benefits in the fields of therapeutic cloning and regenerative medicine.

2. it provides great potential for discovering treatments and cures to a variety of diseases including parkinson disease, spinal cord injuries, diabetes, alzheimer’s disease and many more.

3. limbs and organ could be grown in lab from stem cells and then used in transplant or treat illness.

option number one would be youre best option