Different cell types, for example a muscle or a blood cell in the same organism retain O only a small fraction of their original set of genes, the ones they will need specifically for functioning, but...

Extracted text: Different cell types, for example a muscle or a blood cell in the same organism retain O only a small fraction of their original set of genes, the ones they will need specifically for functioning, but can regenerate these lost genes as needed. O a complete set of all the same genes, but most of the genes have been permanently altered so that they cannot be transcribed into mRNA transcripts. O a complete set of their genes, and retain the ability to express those genes under certain circumstances into MRNA. O the ability to change their DNA to add regulatory elements that can turn off or on genes.