In-Depth Notes on Cloning and Gene Expression

Cloning Development

• Cloning Development: The process whereby a fertilized egg develops into a new individual.

Differentiation

• Differentiation: The process through which cells specialize to become specific types of cells, allowing them to perform unique functions. This process is facilitated by gene regulation.

Stem Cells

• Stem Cells: Unique cells with the ability to develop into various cell types.
  • Embryonic Stem Cells: These cells are totipotent, meaning they can form any type of cell in the body.
  • Adult Stem Cells: These cells are pluripotent, retaining the ability to differentiate into several different types of cells; an example includes bone marrow stem cells.

Cloning Process

• De-differentiation: To create cloned organisms, it's necessary to reverse the differentiation process.

Types of Cloning

• Reproductive Cloning: Process of creating a new individual that is genetically identical to a previous or existing individual.
• Therapeutic Cloning: Involves creating stem cells that are genetically identical to an existing individual, which can then be used to treat various diseases.

Example: Cloning Dolly the Sheep

1. Nucleus Donation: Differentiated adult cells are taken from sheep A, which acts as the nucleus donor, and are grown under starvation conditions to induce a state of de-differentiation.
2. Egg Cell Donation: An egg cell is taken from sheep B (the egg donor), from which the nucleus is carefully removed.
3. Nucleus Insertion: The nucleus from the differentiated cells of sheep A is inserted into the enucleated egg cell from sheep B.
4. Cell Division: The reconstructed egg cell begins to divide, forming an embryo.
5. Embryo Implantation: The embryo is then implanted into the uterus of sheep C, serving as the surrogate mother.
6. Birth of Dolly: The embryo develops within sheep C, resulting in the birth of Dolly, the first cloned mammal.

Role of Activator Proteins

• Activator Proteins / Transcription Factors: Present in the cytoplasm of the egg, these proteins are crucial for initiating the transcription of genes necessary for the development processes that follow fertilization and cloning.