what us natural cloning in plants also called
vegetative propagation
4 examples of vegetative propagation
BULBS e.g daffodils
- leaf base swells with stored food
- buds form internally
- develop into new shoots
RUNNERS e.g strawberry or spider plant
- lateral stem (runner) grows away from parent
- roots develop where runner touches the ground
- plant develops
RHIZOMES e.g marram grass
- specialised horizontal stem underground
- stores food
- buds develop and form new vertical shoots
- these become independent
STEM TUBERS e.g. potato
- tip of an underground stem becomes swollen with food
- forms a tuber
- buds on tuber form nee shoots
how to take plant cuttings
- use non-flowering stem
- make oblique cut between nodes if a healthy stem
- use hormone rooting powder
- place cut end in damp soil
- genetically identical plant grows
(Advantages of using cuttings v seeds)
- faster
- guarantees quality of crop
- by taking cuttings, offspring will be identical
disadvantage if using cuttings v seeds
lack of genetic variation (monoculture)
why is micropropagation used to produce a desirable plant
when the desirable plant: •doesnt readily produce seeds •doesnt respond well to natural cloning •is very rare •is required to he pathogen free •has been GM or selectively bred with difficulty
how are plants artificially cloned?
micropropagation using a tissue culture
method of micropropagation by tissue culture
•small sample of tissue from plant in sterile conditions (explant)
—>meristem tissue(in shoot tips/axial buds)
—> these places are usually virus free
•sample is sterilised
—>bleach
—>ethanol
—>sodium dichloroisocyanurate (this doesnt need to be washes off)
•explant placed in sterile culture medium
—> contains balance or plant hormones that stim mitosis
• cells proliferate
—> forms a mass of identical cells called a
CALLUS
•Callus divided up into individual cells or clumps
—> transferred into a new culture medium
—> contains hormones + nutrients which stim development of plantlets
•plantlets are potted in compost and grow to produce a crop
advantages of micropropagation?
•rapid prod of large no. plants
—>with known genetics
—>so will yield good crop
•prod. disease free plants (done in sterile conditions)
•can prod large numbers of seedless crops
—> for consumer needs
- can grow relativley infertile plants
- increase number of rare/endangered plants
disadvantages of micropropagation
•produces monoculture
—> genetically identical so susceptible to same disease/change in conditions
•expensive process
—> requires skilled workers
•explants/ plantelets vulnerable to moulds/ other diseases during production
•If source plant is infected
—> all clones will be
•large no. of plants can be lost
what us the main form of natural cloning in vertebrates?
formation if monozygotic twins
identical twins
how are monozygotic twins formed
•early embryo splits
—> form two separate embryos
what are two methods of artificial cloning in animals?
artificial twinning
SCNT (somatic cell nuclear transfer)
process of artificial twinning?
•animal with desirable traits treated with hormones
—> animal super-ovulates
—> releasing mature ova
•ova fertilised to form embryo
—> naturally or in a lab
•around day 6 cells are srill totipotent
—>cells of early embryo are split
—> produce smaller embryos
•split embryos are grown in a lab for a few days to ensure they are healthy
•each embryo implanted into a surrogate mother
—> single pregnancies less risky
• embryo develops into foetuses and born naturally
—> identical clones produced my different mothers
what is a difference between artificial twinning and SCNT
AT clones embryos
SCNT can clone adult cells
how are natural twinning and artificial twinning different?
in natural twinning,
—>an early embryo is split and two foetuses grow from these two halves
in artificial twinning,
—>the same thing happens, but the early embryos are split manually
—>the early embryo can also be split into a number of different embryos
—> this can be used to produce a high number identical high quality animals
difference between artificial twinning in cows and pigs
artificial twinning in cows
—> one embryo is implanted into one surrogate
however in pigs
—> tbey naturally produce a litter of piglets
—> so multiple cloned embryos are implanted into one surrogate
what method is used to clone adult animals?
SCNT
- somatic cell nuclear transfer
method of SCNT?
•nucleus is removed from somatic cell of ADULT animal
•nucleus us then placed into ENUCLEATED ovum
•nucleus is given a mild electric shock
—>so nucleus fuses with cell
—> and begins to divide
•embryo that develops
—> transferred to uterus of third animal—> develops to term
•new animal is a clone of animal that gave the nucleus from a somatic cell
what is an enucleated ovum?
ovum with nucleus removed
what is a somatic cell?
a cell in the body that isnt a gamete
diploid cells
why may the cloned animal not be genetically identical to original somatic cell donor
mitochondrial DNA from enucleated ovum from a different animal is still present
what us another name for SCNT
reproductive cloning
—> as final product is a live animal
pros of artificial twinning?
•enables high yielding farm animals to produce many more offspring
• enables the success of male animal passing on desirable genes to be determined
—>if first cloned embryos results in successful breeding animal
—>more identical animals can be bred
