Cloning and biotechnology Flashcards
define clone
genetically identical organisms or cells
what’s vegetative propagation (cloning in plants)
reproduction from vegetative parts of a plant (parts of a plant that do not reproduce sexually)
examples of explants (piece of plant that’s placed in growth medium)
pieces of leaf, stem, root or bud
by which biological process are clones produced
asexual reproduction in which the nucleus divides by mitosis
by which process do yeast reproduce
budding
advantages of reproduction by cloning
- good conditions for growth for parent will be good for offspring
- rapid - population size can increase rapidly
- reproduction can occur with only one parent, also quicker
disadvantages of reproduction by cloning
- overcrowding - more competition
- no genetic diversity (except those caused by mutation)
- little variation
- if environment changes to be less advantageous, whole population is susceptible
- difference between genetic diversity and genetic variation is that the latter refers to how different two alleles of the same gene are, while the former refers to how many genes there are in a population
which tissue allows plants to reproduce by cloning
meristematic tissue
examples of the vegetative parts of a plant
- runners/ stolons
- rhizomes
- suckers
- bulbs
- corms
- leaves
- tubers
what are runners/stolons
horizontal stems that come from roots on surface of ground
what are rhizomes
underground horizontal stems that come from roots
what’s a corm
underground stem with scaly leaves and buds
what are suckers
new stems that grow from the roots
what are bulbs
- underground food stores
what are tubers
underground structures that act as food storage, covered in “eyes”- each eye is able to sprout new plants- potato
where do natural clones grow on leaves
clones grow on leaf margins (edges)
examples of animals produced by natural cloning
- identical twins ( zygote splits into two cells)
- water flea and greenfly
what’s micropropagation
- growing large numbers of new plants from meristem tissue from plant
- takes place after tissue culture
what’s tissue culture
- growing new tissues, organs or plants from certain tissues cut from any part of sample plant
- first step in micropropagartion
how to make cuttings
- choose stem with no leaves to reduce transpiration and no flowers to encourage growth of roots as it takes a lot of energy to grow flowers
- stem cut between two nodes
- may need to dip cut end in rooting hormone or remove bark to encourage plant to produce a callus
- cut end placed in moist soil
- don’t overwater compost to allow air to reach roots
what’s a callus
- soft tissue that forms over a wounded or cut plant surface, leading to healing. A callus arises from cells of the cambium
- (a mass of totipotent cells)
other ways of making cuttings
- root cuttings
- scion cuttings
- leaf cuttings
what are scions
dormant woody twigs
why is tissue culture (micropropagation) used instead of taking cuttings for large scale cloning
- taking cuttings is time consuming and takes up lots of space. Also some plants don’t respond well to taking cuttings
outline the stages in micropropagation
- explant (piece of plant that’s placed in growth medium) cut into small pieces. Meristem tissue is often used, as this is always free from virus infection.
- Explants are sterilised using bleach or alcohol.
- Explants are placed in sterile growth medium (usually agar) contining high concentrations of auxins and cytokinins which stimulate the cells of each explant to divide by mitosis to form a callus.
- Once a callus has formed it is divided
- The cells are placed onto mediums containing different ratios of cytokinin to auxin which stimulates shoot and root growth
- Once tiny plantlets are formed they’re transferred to a greenhouse to be grown in compost or soil until acclimatised
advantages of artificial cloning/ vegetative propagation in plants
- relatively rapid method.
- some plants can’t resproduce sexually
- an unusual/desirable combination of characteristics due to selective breeding or genetic modification can be retained without the risk of losing combination via sexual reproduction.
- new plants are uniform in their phenotype, making them easier to grow and harvest.
- propagation of seedless plants
- quicker than growing from seed
- can be done during any season
- young seedlings less likely to survive
disadvantages of artificial cloning in plants
- Tissue culture is labour intensive.
- may fail due to contamination
- expensive to set up the facilities to perform tissue culture successfully
- clones are susceptible to the same pests/ diseases
- no genetic variation except that introduced by mutation
- cloning of plants requires COMPLEX ASEPTIC TECHNIQUES
what are the 2 main techniques to achieve reproductive cloning in animals
- embryo twinning
- somatic cell nuclear transfer, SCNT (only way to clone adult)
what’s embryo twinning/splitting
splitting an embryo to create two genetically identical embryos
outline embryo splitting/twinning
- Zygote created by IVF, sperm taken from male with desirabe characteristics
- Cells divide by mitosis into ball of cells, incubated in lab.
- Cut up ball of cells at an early stage of development. Cells continue to divide.
- Implant into surrogate.
Offspring = all genetically identical = clones of each other, not of parents.
what’s somatic cell nuclear transfer (SCNT)
transferring nucleus from a somatic cell to an egg cell
what’s enucleation
removal of the cell nucleus
outline SCNT
- Remove nucleus from egg cell (enucleation).
- take normal body cell (adult somatic cell) and remove nucleus.
- Take complete adult somatic cell or nucleus and enucleated egg cell and give them an electric shock to fuse them together
- The cell undergoes mitosis.
- Young embryo is implanted into a surrogate.
- offsting are clones of the original somatic cell
advantage of SCNT over embryo splitting/twinning
- in SCNT, phenotype is known before cloning starts
- in embryo splitting, the precise genotype or phenotype of the offspring produce will depend upon the sperm and egg used. Therefore, the precise phenotype not known.
which type of cells are used for animal cloning
totipotent - cell that can divide and differentiate into all cell types ( only found in embryos in animals)
what can reproductive cloning be useful for
- producing large numbers of:
- farm animals produced by selective breeding or genetic engineering
- genetically-modified animals with unusual characteristics
what’s non-reproductive cloning/ theraputic cloning
- The use of cloned cells for purposes other than reproduction to generate cells, tissues or organs or to replace those damaged by disease or accidents
- tissues grown from the patient’s own cells will be genetically identical and so avoid rejection