6.4 - Cloning and Biotechnology Flashcards
What is a clone? How is it derived and as a result of what type of reproduction?
Genetically identical organisms or cells. Derived by mitosis. Produced by asexual reproduction.
What is vegetative propagation?
Asexual reproduction in plants.
Describe 7 different examples of the production of natural clones in plants that use vegetative propagation.
Runner (or stolen): Horizontal stems that grow on the ground surface & form roots at certain points, e.g. strawberry plant.
Rhizome: Horizontal stems that grow underground. Often used as overwintering organs from which new stems grow from in the spring, e.g. ginger.
Sucker: New stems that grow from the roots of a plant e.g. tomato.
Bulb: An underground swollen stem with stored food and a bud (fleshy), e.g. onion.
Corm: An underground stem with scaly leaves & buds (solid), e.g. crocus.
Leaves: Clones grow on leaf margins. Immature plants drop off & take root, e.g. kalanchoe leaf.
Tuber: Underground stem, often used as a storage organ for nutrients, e.g. potato.
Describe how to take plant cuttings as an example of a simple cloning technique.
Cut a stem between two leaf joints (nodes) at an angle.
Dipping cut end in rooting hormone (IAA) to stimulate root growth.
Place cut end in moist soil.
New roots will grow from stem tissues.
What is grafting? What are the advantages of grafting?
Taking a cutting from one plant and grafting it onto the stem of another. Allows the features of both plants to be available.
What is micro-propagation (tissue culture)?
Growing large numbers of new plants from meristem tissue taken from a sample plant. It is a form of large scale artificial cloning by separating cells and growing them on a growth medium.
Describe the production of artificial clones of plants from tissue culture.
Small pieces of meristematic plant material selected (growing shoot or root) = explants.
Explants are sterilised, aseptic techniques used.
Explants placed on sterile growth medium, containing nutrients & plant growth substances auxin & cytokinin.
Auxin & cytokinin stimulate mitosis and explants form a callus (a mass of undifferentiated, totipotent cells).
Callus is sub-divided.
Small clumps grown on different growth media to encourage roots & then shoots to form.
(100 auxin:1 cytokinin stimulates roots / 4 auxin: 1 cytokinin stimulates shoots)
(auxins stimulate root growth and cytokinins predominantly stimulate shoot growth)
Tiny plantlets form & transferred to a greenhouse to be grown in compost or soil & hardened off.
What are the constituents of the culture medium other than auxin & cytokinin?
Sucrose; amino acids; vitamins; ions / named ions; water; agar.
One disadvantage of micro-propagation is that it can be more expensive than traditional methods. Suggest some factors which may contribute to this extra cost.
Requires lots of skilled workers - labour intensive.
Requires sterile conditions & use of aseptic techniques.
Requires expensive equipment.
Facilities & space to grow & mature plantlets.
Evaluate the production of natural clones.
Advantages: relatively quick so can take advantage of favourable conditions; no reproductive partner has to be found.
Disadvantages: no genetic variation; all susceptible to the same selection pressures; disease, environmental changes.
Evaluate the production of artificial clones.
Advantages: all are clones & so all have same desirable characteristics; high yield, disease resistance; plants that have lost their ability to breed sexually can be reproduced (e.g commercially grown bananas).
Disadvantages: tissue culture is labour intensive + expensive to set up & maintain; tissue culture can fail due to microbial contamination; no genetic variation - all are clones & so all susceptible to the same pests &/or diseases.
How could genetic variation be introduced to both natural & artificial clones?
By a mutation.
Give examples of natural animal clones.
Twins, waterfleas & greenfly.
What natural process does embryo twinning mimic?
The process that results in identical twins.
Describe the process of embryo twinning.
A zygote is created by IVF.
Zygote divides by mitosis to 16 cell embryo.
Individual cells are separated into petri dishes and continue to divide.
Each small mass of cells is then placed into the uterus of a surrogate mother.
Embryos continue to develop & eventually genetically identical offspring are born.
Describe the process of somatic cell nuclear transfer (SCNT).
A somatic cell (non-reproductive cell) is taken from sheep A. The nucleus is extracted and kept.
An egg cell from sheep B has its nucleus removed (encleated).
The nucleus from sheep A and the enucleated egg cell from sheep B are fused using an electric shock and begin dividing normally to form an embryo.
The embryo is implanted into a surrogate mother – the offspring will be a clone of sheep A (as it contains the genetic information from sheep A).