Cloning Flashcards
What is a clone?
An individual that is genetically but not necessarily phenotypically identical to another individual
What are the different mechanisms of cloning?
Natural
Embryo splitting
Reprogramming somatic cells
Nuclear transfer
What are the two types of natural cloning?
Asexual reproduction e.g. hydra bud in spring and summer when conditions are good
Monozygotic twins
What is an example of embryo splitting?
Spemann experiment
How do we reprogram somatic cells in plants?
Treat cells from original plant and treat with growth factor
Grows into a new plant that is genetically identical
What features allow somatic cell nuclear transfer?
Nucleus of every somatic cell contains a complete copy of individual’s genome
Fertilised egg is totipotent
How is somatic cell nuclear transfer carried out?
DNA from one cell is combined with an enucleated fertilised egg
Why is somatic cell nuclear transfer controversial?
Technique is invasive
There are technical problems
Gives rise to ethical dilemmas
How was Megan and Morag created?
Sheep embryo arrested in Go by depriving them of growth factor
Took DNA and transferred into enucleated egg and stimulated to develop
Early embryos placed into uterus of surrogate
Megan and Morag born
Cloned from cultured differentiated embryo cells
How was Dolly created?
Cloned from adult cell
Took cells from adult sheep mammary gland
Arrested in their development
Cells then fused with enucleated eggs (also from adult)
Stimulated them and transplanted into surrogate
Dolly was born
What was Polly?
First transgenic mammal clone
What did Polly’s milk contain?
Human factor IX - treats haemophilia
What are the misunderstandings with cloning?
Clones will not bring back a loved one
Clones are only DNA clones (not cytoplasmic)
Have own mutations
Environment is important
What are some problems with cloning?
Clone has parent telomere so have shorter ones - die earlier
Large foetus syndrome and prolonged gestation
Low success rate (1/277 transnucleated cells for Dolly)
Lack of genetic variation may lead to disease vulnerability
Human cloning may cause psychological problems
Foetus is 10x more likely to die in utero and 3x more likely to die at birth
What are some potential cloning uses?
Developmental research - using clones as controls
Conservation
Cloning elite livestock
Disease resistant farming
Assisted reproductive techniques
Therapeutic cloning
Pharming
Xenotransplantation