Q.20 A cultured skin fibroblast cell of a goat ‘P’ was fused with an enucleated ovum of
a goat ‘Q’. The resultant activated early embryo was then transplanted into a
pseudopregnant (surrogate) female goat ‘R’ of the same strain as ‘Q’. On
completion of gestation, a female goat ‘S’ was born. With the exception of
mitochondrial DNA, ‘S’ is a clone of ________.
(A) Only P
(B) Only Q
(C) Only R
(D) Both P and R
Somatic cell nuclear transfer (SCNT) creates genetic copies excluding mitochondrial DNA. In this goat cloning scenario, the born goat S matches the nuclear donor P.
Correct Answer
The correct option is (A) Only P.
Process Explanation
A cultured skin fibroblast cell from goat P provides the nucleus, fused into an enucleated ovum from goat Q, which supplies cytoplasm and mitochondria. The reconstructed embryo, activated early, gets implanted into pseudopregnant surrogate R (same strain as Q), who gestates but contributes no genetics. Goat S inherits nuclear DNA solely from P, making her a clone of P except for mtDNA from Q’s oocyte.
Option Analysis
| Option | Explanation | Correct? |
|---|---|---|
| (A) Only P | S receives all nuclear DNA from P’s fibroblast nucleus; mtDNA exception from Q noted. Matches SCNT principle. | Yes |
| (B) Only Q | Q donates enucleated ovum (cytoplasm/mtDNA only); nucleus removed, so no nuclear contribution to S. | No |
| (C) Only R | R acts as surrogate for gestation; provides no genetic material, just uterine environment. | No |
| (D) Both P and R | Combines P’s nucleus with R’s irrelevant role; R same strain as Q but non-genetic contributor. | No |
