Q20.3-1CC. - Campbell Biology

Question

Based on current knowledge, how would you explain the difference in the percentage of tadpoles that developed from the two kinds of donor nuclei in Figure 20.16?

Step-by-Step Solution

Answer

Most of the embryos developed into tadpoles when the nucleus was transplanted from a less differentiated cell than the nucleus transplanted from a fully differentiated cell.

 

Thus, the difference in the percentage of tadpoles developed depends on the state of chromatin modification in the cell's nucleus from where the cells were obtained.

Step 1: Outline of the experiment

In the experiment, the eggs of frogs were taken and exposed to UV radiation. As a result, the nuclei of the frog were destroyed. The enucleated egg was then transplanted with nucleic from egg embryo cells and tadpoles.

Step 2: Result of the experiment

It was observed that when the nucleic was transplanted from the embryo cell, most of the eggs developed into tadpoles. On the other hand, only 2% of the eggs developed into tadpoles when the nucleic was transplanted from a tadpole because most of them stopped developing at earlier stages.

Step 3: Explanation for the difference in the percentage of tadpoles developed

When the nuclei are obtained from a relatively undifferentiated cell, most of the cells develop into tadpoles. This exhibits that the chromatin modification state in the nucleus of the intestinal cell was very different from a fertilized egg.

 

Thus, fewer nuclei could reprogram and develop into a tadpole. On the other hand, the chromatin in the nucleus of the embryo was very much similar to that of a fertilized egg. As a result, most of the nuclei could program to form direct tadpoles.