Cloning and Biotechnology Flashcards
What are clones?
Genetically identical organisms or cells
By what process are clones produced?
Clones are produced by asexual reproduction which involves the process of mitosis (for cell division).
2 Identical DNA formed –> 2 Identical Nuclei formed –> 2 Identical cells formed
*If stem cells these may then differentiate into different cells.
Examples of cloning in nature?
When organisms reproduce asexually they produce clones:
- Single celled yeast reproduce asexually via budding
- Bacteria reproduce asexually via binary fission
Advantages of Natural Cloning/Asexual reproduction?
- Good conditions for parent means good condition for the offspring - this is because the parent will already have the genes that allows it to survive and this will be passed onto the offspring directly without change in their genome.
- Rapid reproduction = produce large numbers of offspring to take advantage if suitable environmental conditions
- Requires only one parent
- Can be a backup to sexual reproduction (for organisms that can do both)
Disadvantages of Natural cloning/Asexual reproduction?
- Offspring may be overcrowded
- No genetic diversity = little variation
- Selection is not possible - like no natural selection
- If the environment changes to be less advantageous, the whole population is susceptible.
What is plant cloning by natural vegetative propagation?
The natural asexual reproduction of plant clones from vegetative parts of a plant i.e. from non-reproductive tissues such as roots leaves + stems.
(Not specialised reproductive structures)
Why can plants clone by vegetative propagation?
Many plant cells retain the ability to divide and differentiate (meristem tissues) into a range of different plant cells. This means the plants are able to reproduce by cloning. An adult body cannot do this as they don’t contain many stem cells. This is why a lot more plants reproduce asexually.
What are runners/stolens?
Horizontal stems that run above the ground and produce new clone plants at their nodes (plants form at the nodes of the runner - the roots and the main stem of the cloned plant forms)
What are rhizomes?
Horizontal stems that run below the ground and produce new clone plants at their nodes (new plants form at the nodes of the rhizome - the roots and the main stem of the cloned plant forms)
What are nodes?
The points on a stem where the buds, leaves, branches and roots originate. A small growth zone.
What are suckers?
New stems that grow from the roots or the lower main stem of a plant.
Why are suckers bad sometimes?
Suckers are fast growing, so require lots of nutrients and water. This may cause the original stem to to not recieve enough of the nutrients and water it requires, so may starve and die. This may cause the stem formed as a sucker to become a seperate individual
Why do many plants grow suckers after the main stem has been damaged?
This is because it allows the plant to continue living and growing, even when the parent plant is damaged or dies. The genetic line of that plant is conserved as the stem formed as a sucker will have the same genetic information as the original plant stem.
What are bulbs?
Bulbs consist of an underground stem surrounded by a series of fleshy leaves. They also contain one or more apical bud, that will each grow into plant. New bulbs can develop from the original bulb.
*Look at a diagram on Google images by searching “apical bud of a bulb”
Bulbs are an over-wintering mechanism for perennial monocotyledonous.
What is an overwintering mechanism?
Why are bulbs an overwintering mechanism? FIND ANSWER
An overwintering mechanism is a mechanism by which some organisms survive the winter season, when activity is low and survival would otherwise be difficult.
What are corms?
Corms are swollen underground plant stem with scaly leaves and buds that serve as a storage organ.
This is used by some plants as an overwintering mechanism - corms stay underground in the winter (how is the an overwitnering maechanism) and then in the spring, their buds grow to produce one or more new stems.
When are leaves used for asexual reproduction of plants?
On some plants, their clones grow on teh leaf margins. These immature plant clones then frop off the leaf and take root.
What are tubers?
Tubers are another type of large underground stem/structure that act as a food store for the plant. These tubers can grow into one or more plant and then each plant can produce more tubers.
Name all the methods of natural vegetative propagation and give an example of which plant uses it.
- Runners/Stolons: The Strawberry
- Rhizomes: Bamboo
- Suckers: The Elm Tree
- Bulbs: The onion
- Corms: Root vegetable Taro
- Leaves: The Kalanchoe plant
- Tubers: Potatoes
Examples of natural cloning in animals?
Mammals clone when identical twins are formed - zygote splits to produce two daughter cells which become two separate cell. Each cells grows and develops into a new individual.
- Other animals that naturally clone (asexually reproduce) = the water flea + the greenfly
What is plant cloning by artificial vegetative propagation?
The artificial asexual reproduction of plant clones from vegetative parts of a plant i.e. from non-reproductive tissues such as roots, leaves + stems. This requires human intervention.
Methods of artificial vegetative propagation?
- Cuttings
- Callus Tissue Culture/Micropropagation
*Unsure about grafting
How to take a cutting (simple method)?
1) To make a cutting, a stem (or root, scion or leaf) is cut between two leaf joints (nodes).
2) The cut end of the stem is then dipped in rooting hormone (if required to stimulate growth) before placing that end in moist soil.
3) New roots will grow from the tissues in the stem or around the buried stem, usually from the node to produce a cloned plant.
watch a video or find an aimge to see exaclty whic bit is cut etc.
What is a scion cutting?
Cuttings using a scion rather than a stem - scions are dormant woody twigs.
What is different about leaf cuttings?
- You remove a complete leaf and scoring large veins on the lower leaf surface, and placing that in a growth medium with a warm and moist environment. Once roots have formed, you can plant in soil.
What is tissue culture?
- A series of techniques used to grow cells, tissue or organs from a small sample of cells or tissue.
- Carried out on a nutrient medium under sterile conditions.
- Used commercially to produce large numbers of new plants in micropropagation.
What is micropropagation?
Growing large numbers of plants from meristem tissue taken from a sample plant, using tissue culture.
*Tissue culture usually gets cells/tissues from a plant, places them in culture to multiply + differentiate, allowing a new plant to grow, which is then rooted in soil to produce one plant. Micropropagation is a technique which uses tissue culture, to produce lots of cloned plants. When the cells divide in the culture to one large ball of cells, they are seperated into small clusters of cells (subcultured), each which form a new plant. In tissue culture and micropropagation, meristem cells are usually used.
Stages of micropropagation?
1) Leaf / shoot/ meristem tissue, known as explants, are cut into small pieces. Meristem tissue is usually used as it free from viral infection.
2) Explants are then sterilised using bleach/alcohol to kill any bacteria or fungi which would thrive in the conditions supplied to help the plant grow well.
3) Place sterilised explants in a sterile aseptic growth medium containing nutrients like glucose, amino acids + phosphates. They also contain varying concentrations of auxin and cytokinin which stimulate explants to divide by mitosis to form a callus.
4) The callus is then divided into a large number of small clusters, each made of undifferentiated cells.
5) These small clusters are encouraged to grow divide and differentiate into different plant tissues. This is done by moving the cells for different growth media. The concentration ratio of auxin to cytokinin is used to control which plant tissues will develop.
6) 100 auxin: 1 cytokinin ratio stimulate root formation. 4 auxin: 1 cytokinin ratio stimulate shoot formation.
7) When plantlets, transfer to sterile soil (in greenhouse) to grow.
What is grafting?
A form of asexual reproduction which involves joining the shoot/scion of one plant to the growing stem of another plant.
*How is grafting a form of asexual reproduction? He said it wasn’t and to take it as a seperate concept, not part of artificial vegetative reproduction.
Advantages of artificial cloning?
- Relatively rapid reproduction (faster than from a seed) = tissue culture is much faster than cuttings, but cuttings in general is a fast method of reproduction.
- Backup to sexual reproduction (plant may have lost ability to reproduce sexually/few individuals of plant specie)
- Clones are genetically identical to parent plant = ∴ will display same desirable characteristics.
- The unusual combination of characteristics a plant has due to selective breeding or genetic modification can be retained without the risk of losing that combination in sexual reproduction.
- Uniform phenotype/characteristics means easier to grow and harvest - e.g. same height so can be cut at a specific height for all the genetically identical plants
- If an apical bud is used as an explant and aseptic technique is used, new cloned plant formed from tissue culture will be free from viruses as it contains meristem.
What is the apical bud?
This is the location where shoot growth occurs, usually found at the end of the a shoot.
Disadvantages of artificial cloning?
- Labour intensive
- Expensive to set up facilities to perform successful tissue culture.
- Can fail due to microbial contamination
- Cloned offspring genetically identical = little or no variation (mutation is the only way for variation to occur) susceptible to same pests or disease which would spread rapidly.
Stages of Grafting?
- A stem section of a woody plant (scion) is cut into a wedge
- The root stock is cut to match the scion
- The vascular tissue is lined up
- Binding tape is wrapped around the graft area to hold it in place
Similarities between tissue culture and take cuttings
Tissue culture:
- Requires warm temperatures
- Genetically identical cloned plants are produced
- it’s Thousands of clones can be produced from one plant
- More expensive
- More advanced technology
- Slower method to make cloned plants
- Only require a few cells
Take cuttings: - Requires warm temperatures - Genetically identical cloned plants are produced - Cheaper - Less advanced technology required - Older plants can be used Faster method to make cloned plants - Needs hormones for root growth to speed up process - Requires leaves
Differences between tissue culture and take cuttings
Tissue Culture
- Thousands of clones can be produced from one plant
- More expensive
- More advanced technology
- Slower method to make cloned plants
- Only require a few cells
Take cuttings: - Cheaper - Less advanced technology required - Older plants can be used Faster method to make cloned plants - Needs hormones for root growth to speed up process - Requires leaves
When taking a stem cutting, why are most of the leaves removed?
Most of the leaves are removed from the cutting to reduce water loss. Otherwise, the cutting could dry out very quickly and not grow.
Why is it important to leave some leaves on stem cuttings?
It is important to leave some leaves on cuttings so that photosynthesis occurs to make glucose so new roots can grow.
Suggest reasons why the cuttings should be kept out of direct sunlight.
The cuttings could overheat and lose water; damages very young leaves.
ANIMAL CLONING
What is reproductive cloning?
Reproductive cloning is used to produce genetically identical clone from a donor animal using embryo splitting/twinning or somatic cell nuclear transfer.
Why is cloning useful?
- To increase the number of farm animals with a desirable characteristic (produced from artificial selection/selective breeding or genetic modification)
- Scientists can use cloned animals for research purposes - testing drugs etc.
- Save endangered animals from extinction by cloning new individuals.
Two methods of reproductive cloning?
- Embryo twinning/splitting
- Somatic cell nuclear transfer(SCNT)
Steps of embryo twinning?
1) A zygote (a fertilized egg) is created by in vitro fertilization (fertilization outside a living organism, i.e. in a petri dish)
2) The zygote is allowed to divide by mitosis to form a small ball of cells.
3) The cells are separated and allowed to continue dividing.
4) Each small mass of cells formed is placed into the uterus of a surrogate mother.
5) The embryos continue to develop inside the surrogate mothers and eventually the offspring are born.
6) The offspring are genetically identical to each other. The precise genotype and phenotype of the offspring produced will depend upon the sperm and egg used so they will not be known until the offspring is born
Steps of SCNT in sheep?
1) Differentiated somatic cell is taken from an adult sheep (e.g. udder cell)
2) A ewe is superovulated (using FSH) and egg cells are collected from the ovary / washed out of the oviduct
3) The nucleus is removed from the somatic cell and placed in an enucleated egg cell – an egg cell which has had its nucleus removed.
4) An electric shock is given to fuse the nucleus and the empty egg cell
5) This cell is then placed in a tied oviduct of a ewe to develop into an embryo (in culture)
5) The embryo is then recovered from that ewe and treated with hormones.
6) It is then placed into a surrogate mother’s uterus where it will develop and eventually an offspring will be born.
7) The offspring will be genetically identical to the sheep, which provided the nucleus to be placed in an enucleate egg cell.
Advantage of SCNT over embryo splitting?
The phenotype of the offspring is known before cloning starts. This is not possible with embryo twinning.
- This is the only method that allows cloning of an adult - embryo twinning does not clone adults because the cells of the embryo are formed from random fertilisation which results in the mixing of genetic information from the egg and the sperm - it allows clones of the offspring to be made.
Suggest why an offspring produced through SCNT is not a 100% genetically identical?
- Mitochondrial DNA remains in the enucleated egg cell
- Cloned individual has DNA from the nucleus donor and mitochondrial DNA from the egg donor
What is non-reproductive cloning?
Non-reproductive cloning is the production of cloned cells and tissues for purposes other than reproduction.
Methods of non-reproductive cloning?
Therapeutic Cloning
What is the potential use of therapeutic cloning/reproductive cloning?
- New tissues can be grown to replace dead or damaged tissues - cloned cells have been used to repair damage to nervous tissue in mice (i.e. repair to spinal cord after paralysis) and to regenerate tissue such as that of the heart muscle (after heart attack)
nervous tissue in mice (i.e. spinal cord after paralysis). Skin can be grown in vitro to act as a graft over burned areas - Whole new organs can be grownto replace damaged or diseased ones.
Arguments for artificial cloning in animals?
- We can increase the number of farm animals with a desirable characteristic, as clones retain the same genotype and phenotype of the animal that is cloned.
- Using genetically identical embryos and tissue for research allows the effect of genes and hormones to be assessed with no interference from different genotypes.
- Testing medicinal drugs on cloned cells and tissues avoids using animals or people for testing
- Cells and tissues grown from the patient’s own cells are genetically identical to the donor so can be used in repairing damage caused by disease or injury, without rejection*
- Individuals from an endangered species can be cloned to increase numbers
*e.g. taking stem cells, cloning them by therapeutic cloning, and allowing them to diffferentiate into the correct cells and tissues)
Arguments against artificial cloning in animals?
- Lack of genetic variation, means all members of the herd are susceptible to certain pests or diseases.
- Animals may be produced with little regard for their welfare, which may have undesirable side affects such as meat-producing chickens that cannot walk
- The success rate of adult cell cloning is very poor and the method is a lot more expensive than conventional breeding. (DOES THE TERM ‘ADULT CELL CLONING’ REFER TO BOTH EMBRYO TWINNING AND SCNT?)
- 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.
- This 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
