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Mitochondrial DNA genotypes in nuclear transfer-derived cloned sheep
M J Evans1, C Gurer, J D Loike
1Integrated Program in Cellular, Molecular and Biophysical Studies, Columbia University College of Physicians and Surgeons, 630 West 168th Street, New York, New York 10032, USA.
Nature Genetics
|September 2, 1999
Summary
Cloned mammals, like Dolly, possess nuclear DNA from donor cells but exclusively mitochondrial DNA (mtDNA) from recipient egg cells. This nuclear transfer process results in genetic chimerism, not full genetic replication.
Area of Science:
- Cell Biology
- Genetics
- Reproductive Biology
Background:
- Eukaryotic cells have two genomes: nuclear DNA (nDNA) and mitochondrial DNA (mtDNA).
- nDNA follows Mendelian inheritance, while mtDNA is maternally inherited.
- Mammalian cloning via nuclear transfer involves fusing a donor cell with an enucleated oocyte.
Purpose of the Study:
- To investigate the origin of mitochondrial DNA (mtDNA) in cloned mammals.
- To determine if mtDNA is transferred from donor somatic cells during nuclear transfer.
- To analyze the mtDNA genotype of Dolly and other nuclear transfer-derived sheep.
Main Methods:
- Nuclear transfer technique using somatic cells (adult and fetal) and enucleated oocytes.
- Analysis of mtDNA genotype in cloned sheep.
- Comparison of mtDNA from donor cells and recipient oocytes.
Main Results:
- All ten nuclear transfer-derived sheep, including Dolly, exclusively possessed mtDNA from the recipient oocytes.
- No detectable contribution of mtDNA from the somatic donor cells was found.
- The cloned sheep were confirmed as authentic nuclear clones.
Conclusions:
- Mammalian cloning via nuclear transfer results in exclusive maternal inheritance of mtDNA.
- Cloned animals are genetic chimeras, with nuclear DNA from the donor and mtDNA from the recipient.
- This finding clarifies the genetic makeup of cloned mammals and the process of nuclear transfer.