Question

A population of inner cell mass from the blastocyst of a mouse strain "A" was microinjected in a blastocyst of mouse strain "B". The blastocysts was then implanted in a pseudopregnant mouse of strain "B". The pups finally produced are called

• A. Mosaic
• B. Chimeric
• C. Tetraploid
• D. Aneuploid

Hint:

Chimera vs Mosaic:
Chimera = Cells from TWO distinct zygotes mixed experimentally.
Mosaic = Genetically distinct cells arising from ONE single zygote.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Genetic chimerism in transgenic animal models results from combining embryonic cell lineages derived from two or more distinct zygotes.

Step 2: Detailed Explanation:
In mammalian developmental genetics and transgenesis:
1. Chimeric Animal (Chimera): An individual organism whose body tissues are composed of cell populations derived from two or more genetically distinct fertilized zygotes (e.g., microinjecting inner cell mass or embryonic stem cells of strain A [e.g., agouti coat] into host blastocysts of strain B [e.g., black coat]).
2. Mosaic: An organism with genetically different cell lines arising from a single zygote due to somatic mutation or X-chromosome inactivation.

Step 3: Final Answer:
Therefore, the resulting pups are called Chimeric, matching option (B).