Chimera production typically involves introducing embryonic stem cells into which embryonic stage?

Chimera production typically involves introducing embryonic stem cells into which embryonic stage?

• A. Zygote
• B. Morula
• C. Blastocyst
• D. Four-cell embryo

Answer: (C)

Chimera production relies on placing pluripotent embryonic stem cells into an embryo at a stage where they can integrate into the developing body and contribute to most tissues. Embryonic stem cells are derived from the inner cell mass of the blastocyst, and injecting them into a blastocyst puts them into a structure with a defined inner cell mass and a surrounding cavity, allowing the introduced cells to mix with the host cells and become part of the embryo proper. At the zygote stage, there is only one cell, so introducing new cells isn’t conducive to forming a mixed lineage. The morula stage lacks the blastocoel cavity needed for efficient injection and integration. The four-cell stage is too early for stable incorporation into the developing inner cell mass. The blastocyst stage provides the right environment and timing for the ES cells to contribute to the embryo and, potentially, the germ line, making it the standard stage for generating chimeras.

Chimera production relies on placing pluripotent embryonic stem cells into an embryo at a stage where they can integrate into the developing body and contribute to most tissues. Embryonic stem cells are derived from the inner cell mass of the blastocyst, and injecting them into a blastocyst puts them into a structure with a defined inner cell mass and a surrounding cavity, allowing the introduced cells to mix with the host cells and become part of the embryo proper.

At the zygote stage, there is only one cell, so introducing new cells isn’t conducive to forming a mixed lineage. The morula stage lacks the blastocoel cavity needed for efficient injection and integration. The four-cell stage is too early for stable incorporation into the developing inner cell mass. The blastocyst stage provides the right environment and timing for the ES cells to contribute to the embryo and, potentially, the germ line, making it the standard stage for generating chimeras.