Control of Gene Expression. S0matic cell nuclear transfer. Cloning. Somatic Cell Nuclear Transfer. Researchers clone animals by nuclear transplantation SOMATIC CELL NUCLEAR TRANSFER: A nucleus of an egg cell is replaced with the nucleus of a somatic cell from an adult
Nucleus fromdonor cell
Implant blastocystin surrogate mother
Clone of donoris born(REPRODUCTIVEcloning)
Add somaticcell fromadult donor
Grow in culture to producean early embryo (blastocyst)
Remove embryonic stem cells from blastocyst andgrow in culture
Induce stemcells to formspecialized cellsfor THERAPEUTICuse
Reproductive vs. Therapeutic Cloning
Tadpole (frog larva)
Frog egg cell
The first mammalian clone, a sheep named Dolly, was produced in 1997
Dolly provided further evidence for the developmental potential of cell nuclei.
Heart muscle cells
Different types ofdifferentiated cells
DNA packing in eukaryotic chromosomes helps regulate gene expression.
A chromosome contains a DNA double helix wound around clusters of histone proteins.
DNA packing tends to block gene expression.
“Beads ona string”
Tight helical fiber(30-nm diameter)
TWO CELL POPULATIONSIN ADULT
Cell divisionandX chromosomeinactivation
Allele fororange fur
Allele forblack fur
In female mammals, one X chromosome is inactive in each cell.
An extreme example of DNA packing in interphase cells is X chromosome inactivation
Useful in genetic engineering where DNA of one organism is inserted into the DNA of another organism (recombinant DNA)
Example: EcoRI restriction enzyme cuts a GAATTC sequence
Restriction enzymes are found naturally in bacteria cells. The bacteria developed the enzymes to fight against viruses. They chop up the viral DNA that gets inserted into their cells.
Electrical currents run through the DNA samples that have been cut into fragments. Smaller fragments travel more quickly from the – electrode to the + electrode.
Separated fragments can be studied or combined with other fragments to create recombinant DNA.
Learning the sequence of DNA fragments can allow scientists to understand the function of certain sequences of bases.
Restriction enzymes are used to cut large DNA strands into shorter fragments.
Dyes are used to color known bases, and the known colored known bases bind to the unknown sequence. The unknown sequence can be read by following complementary base-pairing rules.
Purpose: create copies of selected DNA segments when the sample size of DNA is too small to run all of the needed tests
Uses a thermal cycler to separate the DNA double helix and DNA polymerase enzymes to create copies of the selected segments.
Extremely useful in forensic science and medicine