Cloning and Biotechnology Flashcards
Asexual reproduction
A form of cloning and it results in offspring produced by mitosis and known as clones - organisms that are genetically identical to each other and the parent organism
Natural Cloning
Vegetative propagation - occurs in many species of flowering plants - a structure forms which develops into a fully differentiated new plant which is genetically identical to the parent
Where can new plant be propagated from?
Stem, leaf, bud or root of parent ; eventually becomes independent from its parent (strawberries and spider plants)
What is special about vegetative propagation?
Perennating organs are involved - which enable plants to survive adverse conditions - contain stored food from photosynthesis and can remain dormant in the soil ; allow survival from one season to the next
Bulbs?
Bulbs - daffodil - leaf bases swell with stored food from photosynthesis and buds form internally which develop into new shoots and new plants
Rhizomes?
Marram grass is an example - rhizome is a specialised horizontal stem running underground, often swollen with stored food ; buds develop and form new vertical shoots which become independent plants
stem becomes swollen Stem tubers?
The tip of an underground stem becomes swollen with stored food to form a tuber or storage organ ; buds on the storage organ develop to produce new shoots
How do farmers exploit cloning?
Take cuttings of many plants - short sections of stems are taken and planted either directly in the ground (sugar cane) or in pots - rooting hormone is often applied to the base of a cutting to encourage growth of new roots
Advantages of propagation
It is much faster - time from planting to cropping is reduced and also guarantees the quality of plants - offspring will be genetically identical to good stock and thus will crop well
Disadvantage of propagation
Lack of genetic variation in the offspring should any new disease or pest appear or if climate change occurs
Practical cloning techniques
Use a non-flowering stem - energy spent on developing flowers instead of rooting
Make an oblique cut in the stem
Use hormone rooting powder
Reduce leaves to two or four
Keep cutting well watered
Cover the cutting with a plastic bag for a few days - moist warm conditions
How have scientists developed ways to produce huge numbers of clones from one plant?
Using the fact that many plant cells are totipotent and thus can differentiate into all of the different types of cells in the plant
Micropropagation
Process of making large numbers of genetically identical offspring from a single parent plant using tissue culture techniques
When is Micropropagation used?
When a desirable plant does not readily produce seeds or doesn’t respond well to natural cloning and is very rare - or when it is required to be pathogen free by growers
What is a basic protocol used for Micropropagation?
Sodium dichloroisocyanurate which keeps the plant tissues sterile without being in a sterile lab so it is extremely useful for scientists in the field working with rare and endangered plant material
Basic principles of Micropropagation
Take a small sample of tissue from the plant you want to clone ; meristem tissue from shoot tips/axial buds is often dissected out in sterile conditions to avoid contamination
Sample is sterilised in bleach/ethanol ; with sodium dichloroisocyanture it remains sterile and the material removed from the plant is called the explant
Explant is placed in a sterile culture medium containing plant hormones which stimulate mitosis and the cells proliferate forming a callus (identical cell mass)
Callus is divided and individual clumps are transferred to a new medium containing a different mixture of hormones/nutrients to produce tiny/genetically identical plantlets
Plantlets are potted into compost where they grow into small plants and they are then used to produce crops
Scale of micropropagation?
Increasing to take place in bioreactors which make artificial embryo plants to be packaged in artificial seeds
Arguments for micropropagation?
Rapid production of large number of plants which will yield good crops
Culturing meristem tissue produces disease free plants
Produces many new plants which are seedless and thus sterile to meet consumer tastes
Provides way of growing plants which are naturally relatively infertile/difficult to grow from seeds
Provides reliably increasing the number of rare or endangered plants
Arguments against micropropagation?
Produces a monoculture ; many plants which are genetically identical so they are all susceptible to the same diseases
Relatively expensive process and requires skilled workers
E plants and plantlets vulnerable to infection by moulds and other diseases
If source material is infected with a virus all of the clones will also be infected
Large numbers of plants may be lost
Cloning in invertebrates
Some animals such as starfish can regenerate entire animals from fragments of the original if they are damaged - flatworms and sponges fragment and form new identical animals as part of their normal reproductive process (all clones)
How do hydra reproduce?
They produce buds on the side of their body which develop into genetically identical clones ; many differences between mother and daughter due to high mutation rates (so not real clones)
Main form of vertebrate cloning?
Monozygotic twins (identical twins) - early embryo splits to form two separate embryos - incidence varies between species
Why might monozygotic twins look different?
As a result of differences in their position and nutrition in the uterus
Asexual reproduction example?
Some female amphibians and reptiles will produce offspring when no male is available (often males but all genetic info from the mother)
