6.4 Cloning and biotechnology Flashcards
define clones
genetically identical organisms or cells
how are clones produced
by asexual reproduction in which the nucleus is divided by mitosis where is creates two identical copies of DNA. These cells may not always be physically or chemically identical as, after division, they may differentiate to form two different types of cell
What is an example of cloning
yeasts reprudce by budding
bacteria reproduce by binary fission
what are advanatages of natual cloning
-if the conditions for growth are good for the parent, they will also be good for the offspring
-cloning is relatively rapid so the population can increase quickly to take advanatage of the suitable environmental conditions
-reproduction can be carried out even if there is only one parent
what are the disadvantages of natural cloning
-the offspring may become overcrowded
-there will be no genetic diversity (except for when theres mutation)
-the population shows little variation
-selection is not possible
-if the environment changes to be less advanatgeous as the whole population is susceptible
what is vegetative propagation
the process of reproduction through vegetative parts of the plant, rather than through specialised reproductive structures
What are runners, stolen and rhizomes?
-horizontal stems that can form roots at certain points
-they are called stolens of they grow on the surface of the ground
-they are called rhizomes if they are underground
How are some rhizomes adapted?
-they are thickened over-wintering organs from which one of more new stems will grow in the spring
what are suckers?
-new stems that grow from the roots of a plant
-these may be close to the base of an older stem or could be some distance away
-in all cases, the original horizontal branch may die, leaving the new stem as a separate individual
Describe Bulbs
-an over-wintering mechanism for many perennial monocotyledonous plants
-they consist of an underground stem from which grow a series of flesh leaf bases
-they have an apical bud which will grow into a new plant in the spring
-often a bulb contains more that one apical bud and each will grow into a new plant
Describe Corms
-solid rather than fleshy like a bulb
-they are an underground stem with scaly leaves and buds
-they remain in the ground over winter
-in the spring, the buds grow to produce one or more new plants
-croci and gladioli reproduce using corms
Describe leaves
-Kalanchoe plant reproduces asexually as clones grow on the leaf margins
-the immature plants drop off the leaf and take root
Describe Tubers
-another type of underground stem
-potatoes are tubers
-one potato will grow into one or more plants
-each new plant can then produce many new tubers
Describe cloning in animals
-do not clone as often as plants
-mammals clone when identical twins are formed
-occurs when a zygote divides as normal but two daughter cells then split to become two separate cells
-each cell grows and develops into a new individual
-the water flea and greenfly are examples of animals that commonly reproduce asexually to produce clones
Define micropropagation
growing large numbers of new plants from meristem tissue taken from a sample plant
Define tissue culture
growing new tissues, organs or plants from certain tissues cut from a sample plant
What is the easiest way to create clones?
-through making cuttings
-to make a cutting, a stem is cut between two leaf joints (nodes)
-the cut end of the stem is then placed in moist soil
-new roots will grow from the tissues in the stem (usually from the node) but they may grow from other parts of the buried stem
What are cuttings used for?
To produce large numbers of plants very quickly
What other treatment may some plants need as well as making cuttings?
-dipping the cut stem in rooting hormone to help stimulate root growth
-may be helpful to wound or remove the bark from the cut end of the stem as this encourages the plant to produce a callus
What parts of the plant can be used to make cuttings?
-Root cuttings, a section of root is buried just below the soil surface and produces new shoots
-scion cuttings, which are dormant woody twigs
-leaf cuttings, a leaf is placed on moist soil. the leaves develop new stems and new roots. some leaves may produce many new plants from one cutting
Why is cloning by taking cuttings not alway appropriate?
-can be time consuming
-needs a lot of space
-some plants don’t respond well to taking cuttings
How is tissue culture carried out?
-carried out on a nutrient medium under sterile conditions
-application of plant growth substances at the correct time can encourage the cells in the growing tissue to differentiate
-it is widely used commercially to increase the number of new plants
What does micropropagation involve?
- Suitable plant material is selected and cut into small pieces (explants) Meristem tissue is often used as it is always free virus infection
2.They are sterilised using dilute bleach or alcohol- essential to kill any bacteria and fungi, as these would thrive in the conditions supplied to help the plant grow well - They are placed on a sterile growth medium containing suitable nutrients such as glucose, amino acids and phosphates. The gel contains high concentrations of he plant growth substances auxin and cytokinin which stimulates the cells of each explant to divide by mitosis to form a callus.
4.Once a callus has formed, it is divided to produce a larger number of small clumps of undifferentiated cells
5.These clumps of cells are stimulated to grow, divide and differentiate into different plant tissues. This is achieved by moving the cells to different growth media. each medium contains different ratios of auxin and cytokinin. The first medium contains the ratio 100 auxin: 1 cytokinin, and this stimulates roots to form. The second medium contains the ratio of 4 auxin: 1 cytokinin which stimulates the shoots to form. - Once tiny platelets have been formed, these are transferred to a greenhouse to be grown in compost or soil and acclimatised to normal growing conditions
What are explants?
-can be tiny pieces of leaf, stem, root or bud
What are advantages of artificial cloning?
-rapid method of producing new plants rather than growing them from seed
-can be carried out where sexual reproduction is not possible e.g commercially grown bananas
-plants selected will be genetically identical to the parent plant- display same characteristics eg. high yield, resistance to disease and colour
-new plants are uniform in their phenotype which makes them easier to grow and harvest
-using the apical bud as an explant for tissue culture ensures the new plants are free from viruses
What are disadvantages of artificial cloning?
-tissue culture is labour intensive
-expensive to set up the facilities to perform tissue culture
-cloned offspring are genetically identical so are susceptible to same pests/disease
-crops grown in monocultures allow rapid spread or a disease
-no genetic variation, exceptions of mutation
define embryo twinning
splitting an embryo to create two genetically identical embryos
define enucleation
removal of the cell nucleus
define somatic cell nuclear transfer
a technique that involves transferring the nucleus from a somatic cell to an egg cell
What may cloning of animals be useful for?
-elite farm animals produced by selective breeding or genetic modification eg. a bull whose value is as a stud, supplying sperm for artificial insemination
-genetically-modified animals developed with unusual characteristics eg. cows that produce less methane
What are the 2 main techniques to achieve reproductive cloning?
-embryo twinning (produce identical offspring)
-somatic cell nuclear transfer (only way to clone an adult)
Describe how Embryo splitting is done
- a zygote is created by IVF
- The zygotę is allowed to divide by mitosis to form a small ball of cells
- The cells are separated and allowed to continue dividing
- Each small mass of cells is placed into the uterus of a surrogate mother
What has Embryo splitting been used for?
-to clone elite farm animals or animals for scientific research.
-precise genotype and phenotype of offspring is unknown until animals are born as they depend on the sperm and egg used
Describe Somatic cell nuclear transfer
- An egg cell is obtained and its nucleus is removed (enucleation)
- A normal body cell (somatic cell) from the adult to be cloned is isolated and may have the nucleus removed
- The complete adult somatic cell or its nucleus is fused with the empty egg cell by applying an electric shock
- The shock also triggers the egg cell to start developing, as though it had just been fertilised
- The cell undergoes mitosis to produce a small ball of cells
- The young embryo is placed into the uterus of a surrogate mother
What is non-reproductive cloning?
The production of cloned cells and tissues for purposes other than reproduction
What is therapeutic cloning?
When new tissues can be grown as replacement parts for people who are not well:
-Skin can be grown in vitro to act as a graft over burned areas
-cloned cells have been used to repair damage to the spinal cord of a mouse and to restore the capability to produce insulin in the pancreas
-There is potential to grow whole new organs to replace diseased organs
-Tissues grown from the patients own cells will be genetically identical and so avoid rejection, which battles the problem when transplanting donated organs
How can cloning be used for scientific research?
-research into the action of genes that control development and differentiation
-used to grow specific tissues or organs for use in tests on the effects of medicinal drugs
What are the arguments for artificial cloning in animals?
-can produce a herd of animals with a high yield or showing an unusual combination of characteristics
-produces genetically identical copies of very high value individuals containing the same characteristics
-using genetically identical embryo and tissues allows the effects of genes and hormones to be assessed with no interference of other genotype
-testing medicinal drugs on clones cells avoids using animals for testing
-can produce cells genetically identical to the donor to repair damage from accidents
-individuals of endangered species can be cloned to increase numbers
What are the arguments against artificial cloning in animals?
-lack of genetic variation may expose herd to certain diseases or pests
-animals may be produced with little regard for their welfare (eg chickens used for meat unable to walk)
-success rate of adult cell cloning is very poor and method is more expensive than breeding
-cloned animals may be less healthy and have shorter life spans
-there are ethical issues regarding how long the embryo survives and whether it is right to create a life simply to destroy it
-does not help increase genetic diversity
Define biotechnology
the use of living organisms or parts of living organisms in industrial processes. This could be to produce food, drugs or other products
How are microorganisms in food used in biotechnology?
-ethanol in beer and wine
-co2 used to make bread rise
-lactic acid used to make yoghurt and cheese
-soya beans are fermented to produce soy sauce
How are microorganisms in pharmaceutical drugs used in biotechnology?
-penicillin
-other antibiotics
-insulin, other therapeutic human proteins
How are microorganisms in enzymes used in biotechnology?
-protease and lipase used in washing powders
-pectinase used to extract juice from fruit
-sucrase used to digest sugar to make food sweeter
-amylase to digest starch into sugar to produce syrup used as a sweetener
-protease used to tenderise meat
-lactase to make lactose-free milk