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Multiple Choice
The efficiency of cloning, and the ability to generate healthy cloned animals, has been largely hampered by the difficulty of __________.
A
inducing recombination in differentiated donor cells in order to restore the full genomic complement
B
transforming donor cells with genes encoding proteins required for normal embryonic development
C
physically removing the nucleus from the egg cell that will ultimately receive the donor cell nucleus
D
implanting the clone into the surrogate mother
E
completely reversing epigenetic alterations in donor cell nuclei such as DNA methylation and chromatin packing
Verified step by step guidance
1
Understand the context of cloning: Cloning involves creating a genetically identical copy of an organism. This process typically involves transferring the nucleus from a donor cell into an egg cell that has had its nucleus removed.
Identify the challenge in cloning: The main difficulty in cloning is not just the technical aspects of transferring nuclei or implanting embryos, but rather the biological challenge of reversing epigenetic modifications in the donor cell nucleus.
Define epigenetic alterations: Epigenetic changes, such as DNA methylation and chromatin packing, affect gene expression without altering the DNA sequence. These modifications need to be reset to allow the cloned embryo to develop properly.
Explain the importance of reversing epigenetic changes: For a cloned animal to develop normally, the epigenetic state of the donor nucleus must be reprogrammed to resemble that of a fertilized egg, which involves removing or altering these epigenetic marks.
Conclude with the impact on cloning efficiency: The inability to completely reverse these epigenetic changes is a major barrier to successful cloning, as it can lead to developmental abnormalities or failure to develop entirely.