Exam 3 - Cloning Flashcards
What is the “rejection problem” with stem cells and how can we get around it?
transplanted stem cells may cause immune rejection, so patients would have to take immunosuppressive drugs which present their own dangers
therapeutic cloning would create embryonic stem cells that are genetically identical to the patient
What is the difference between reproductive and therapeutic cloning?
reproductive: tech used to generate an individual who has the same nuclear DNA as another existing individual
therapeutic: generation of human embryos for use in research to harvest stem cells that can be used to study human development and treat diseases
What is SCNT?
somatic cell nuclear transfer
a secondary M2 oocyte (1n, 2 chromatids per chromosome) is enucleated
a diploid somatic cell (2n) has its nuclear information transferred into the enucleated oocyte using electrical fusion, the first polar body is either removed or degenerates
can be developed into a day 5 embryo for transfer to the uterus which may result in pregnancy
Why might a clone using SCNT not be completely identical?
mitochondria contain their own DNA and are only passed on by the mother, so some of the genetic material comes from whichever organism provided the oocyte
How many protein coding genes are in the mitochondrial DNA vs the nuclear DNA?
13 in the mito DNA,
23,000 in the nuclear DNA
What can be caused by mutations in mitochondrial DNA?
neurological, muscle, and heart problems
deafness
type 2 diabetes
If a male has a mitochondrial disease, who will he pass that disease to?
nobody
How can we prevent the transmission of mitochondrial diseases? Is it considered cloning?
mitochondrial replacement
not cloning because a sperm still fertilizes an egg
What is mitochondrial replacement? What is the process and what does it accomplish in the end?
donor oocyte is enucleated
spindle chromosomes are removed from the intended mother oocyte and injected into the donor oocyte with viral fusion
sperm is injected into the oocyte causing fertilization
blastocyst develops and embryo is implanted into the intended mother
end up with genetic contribution from 3 parents: intended mother with a mitochondrial disease contributes 23 chromosomes of nuclear DNA, intended father contributes 23 chromosomes of nuclear DNA, and a female egg donor contributes normal mitochondria
Who was the Dr. who did mitochondrial replacement, when, and what did it accomplish?
Dr. John Zhang, 2016, baby born free of Leigh syndrome
Where does the nuclear DNA come from in cloning vs. mitochondrial replacement?
cloning - from a single somatic cell of an individual
mitochondrial replacement - from an oocyte and a sperm of two individuals
What is gene therapy?
treat or prevent diseases by…
- replacing mutated genes that cause a disease with a healthy copy
- inactivating a mutated gene
- introducing new genes to help fight a disease
What is cell therapy?
cellular material is injected into a diseased patient
healthy cells integrate into the site of injury, replacing damaged tissue and facilitating improved function of an organ or tissue
How can therapeutic cloning and gene therapy be used to treat a genetic disease?
- somatic cells are taken from a patient with a genetic mutation
- somatic cell nuclear transfer into a enucleated donor oocyte
- embryonic stem cells from the ICM are isolated
- gene therapy (repair the mutation, giving us cells with the normal gene)
- cells are differentiated into the needed cell
- cell therapy (healthy cells are injected into the patient)
What types of cells can be targeted for gene therapy? What results will it cause?
somatic cells - adult stem cells, only treats the disease in the affected individual
germline - targets zygotes or gametes, modifies all cells in a new organism including the sperm or eggs so that the offspring and all of the future generations are treated (but not the affected person)
