Question

In cloning, reprogramming of somatic nucleus is achieved by

• A. Cytoplasmic factors in oocyte
• B. DNA polymerase
• C. Ribosomes
• D. Growth hormones

Hint:

Remember: \[ \boxed{ \text{Somatic Nucleus} + \text{Enucleated Oocyte} \Longrightarrow \text{Cloned Embryo} } \] The cytoplasm of the oocyte contains the factors necessary for nuclear reprogramming.

Answer 1

The Correct Option is A

Concept: Somatic Cell Nuclear Transfer (SCNT) is the technique used in animal cloning. In this method, the nucleus of a differentiated somatic cell is transferred into an enucleated egg (oocyte). The cytoplasm of the oocyte contains special proteins and regulatory molecules that reprogram the adult nucleus, restoring its ability to direct the development of an entire organism.

Step 1: Understand Somatic Cell Nuclear Transfer (SCNT).
The cloning process involves the following steps: \[ \boxed{ \text{Remove nucleus from oocyte} \rightarrow \text{Insert somatic nucleus} \rightarrow \text{Activation} \rightarrow \text{Embryo development} } \] The transferred nucleus initially contains genes specialized for a particular tissue, but after entering the oocyte, it regains the characteristics of a fertilized egg nucleus.

Step 2: Role of cytoplasmic factors.
The cytoplasm of the oocyte contains:
• Reprogramming proteins
• Maternal mRNA
• Regulatory enzymes
• Epigenetic modifiers These factors erase many of the differentiated characteristics of the somatic nucleus and activate genes required for embryonic development.

Step 3: Eliminate incorrect options.

• DNA polymerase only synthesizes DNA and does not reprogram the nucleus.
• Ribosomes synthesize proteins but cannot alter nuclear identity.
• Growth hormones regulate growth but do not induce nuclear reprogramming.
• Therefore, cytoplasmic factors present in the oocyte are responsible for reprogramming. Final Answer: \[ \boxed{Option (A) is correct \]