Edexcel iGCSE Biology-6.19B-6.20B The Production of Cloned Mammals- Study Notes- New Syllabus
Edexcel iGCSE Biology-6.19B-6.20B The Production of Cloned Mammals- Study Notes- New syllabus
Edexcel iGCSE Biology-6.19B-6.20B The Production of Cloned Mammals- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
6.19B describe the stages in the production of cloned mammals involving the introduction of a diploid nucleus from a mature cell into an enucleated egg cell, illustrated by Dolly the sheep
6.20B understand how cloned transgenic animals can be used to produce human proteins
Production of Cloned Mammals
📌 Introduction
Cloning in mammals produces an organism genetically identical to the donor animal.
Famous example: Dolly the sheep (first mammal cloned from an adult cell in 1996).
Method used: Somatic Cell Nuclear Transfer (SCNT).
🧩 Step-by-Step Process
- Isolation of Diploid Nucleus
A mature somatic cell (e.g., udder cell) is taken from the donor animal.
The nucleus of this cell, containing diploid DNA, is extracted. - Enucleation of Egg Cell
An egg cell is taken from a female sheep.
Its nucleus is removed, leaving an enucleated egg (cytoplasm only). - Nuclear Transfer
The diploid nucleus from the donor cell is inserted into the enucleated egg.
This forms a reconstructed egg with the donor’s DNA. - Stimulation of Cell Division
The reconstructed egg is stimulated (e.g., electrically) to divide and form an embryo.
Embryo undergoes mitotic divisions, developing into a multicellular structure. - Implantation into Surrogate Mother
The embryo is implanted into the uterus of a surrogate mother.
The surrogate carries the embryo to term. - Birth of Cloned Animal
Offspring is genetically identical to the donor animal.
Example: Dolly the sheep, clone of an adult Finn Dorset sheep.
⚡ Key Points
- Cloning = production of genetically identical organism
- Technique used: Somatic Cell Nuclear Transfer (SCNT)
- Uses:
- Preserve elite livestock traits
- Research in medicine and genetics
- Limitations:
- Low success rate
- Ethical concerns
⚡ Quick Recap
Dolly the sheep → first cloned mammal from adult somatic cell
Steps: Donor nucleus → enucleated egg → reconstruct → divide → implant → birth
Outcome: genetically identical to donor
Purpose: preserve traits, research, medical applications
Cloned Transgenic Animals for Human Protein Production
📌 Introduction
Cloned transgenic animals are animals that:
– Are genetically identical to a donor (cloned).
– Have foreign genes inserted (transgenic) that allow them to produce human proteins.
Purpose: produce medically important proteins in large quantities.
Example: goats producing human antithrombin in milk.
🧩 How It Works
- Creating the Transgenic Animal
Human gene for the desired protein is isolated.
Inserted into the embryo of an animal using molecular techniques.
Embryo develops into a transgenic animal expressing the protein in milk, blood, or eggs. - Cloning for Consistency
Transgenic animals can be cloned to produce multiple animals with the same inserted gene.
Ensures uniform, predictable protein production. - Protein Collection
Protein is collected from:- Milk (e.g., antithrombin)
- Blood (e.g., clotting factors)
- Eggs (e.g., lysozyme)
⚡ Advantages
- High yield of human proteins
- Ethically safer than harvesting from humans
- Can produce proteins for rare diseases
- Cloning ensures consistent quality
⚡ Quick Recap
Cloned transgenic animals = cloned + genetically modified
Purpose: produce human proteins for medicine
Process: insert human gene → transgenic animal → clone → collect protein
Examples: human antithrombin in goat milk, clotting factors in blood