6.2.1. cloning

define a clone

offspring, produced by mitosis, that is genetically identical to the parent plant

define asexual reproduction

the generation of new individuals, often naturally, using mitosis to produce clones

define reproductive cloning

using artificial cloning methods to produce 2 or more individuals that are clones of each other

define vegetative propagation

the production of plant clones from non-reproductive tissues

define perennating organ

plant structures which allow them to survive adverse conditions, they contain stored food and can remain dormant in the soil

define horticulture

the branch of agriculture that deals with plants

define agriculture

the cultivation and breeding of animals, plants or fungi for food or other resources

define taking cuttings

removing and planting short sections of stem of a plant in order to produce clones of that plant

what are types of vegetative propagation methods

bulbs, runners, rhizomes, tubers, suckers, stolons

how do rhizomes work

a specialised horizontal stem running underground, often swollen with stored food, buds develop and form new vertical shoots which become independent plants

how do runners work

a lateral stem grows away from the parent plant, roots develop where runner touches the ground, new plant develops- runner eventually withers away leaving new individual independent

example of plants that use rhizomes

marram grass

example of plants that use runners

strawberry, spider plant

how do bulbs work

leaf bases swell with stored food from photosynthesis, buds form internally which develop into new shoots and new plants in next growing season

examples of plants that use bulbs

daffodils, onions

how do tubers work

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

example of plants that use tubers

potatoes

why is natural cloning in plants common but rare in animals

plants have totipotent cells in many places so can differentiate into all different types of cell in a plant, whereas in animals totipotent cells are only found in early embryonic tissue

what is natural cloning in plants often called

vegetative propagation

how are natural clones used in horticulture

splitting up e.g. bulbs or removing young plants from runners, taking cuttings/artificial vegetative propagation

what is the process of taking cuttings/artificial vegetative propagation

• short sections of stems are taken containing a growing bud

• cut edge dipped in rooting hormone powder to encourage growth of new roots

• cutting often planted directly into compost in a pot or soil outside

• roots grow and the cutting is now a complete plant that is a clone of the parent plant

what are the ways of improving success rates of taking cuttings

• use a non-flowering stem

• 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

how does using a non-flowering stem improve success rates of cuttings

resources like glucose are not needed to make and sustain the cells of flowers (don’t photosynthesis so don’t make glucose for themselves), so more can be used to support root growth

how does making an oblique cut in the stem improve success rates in cuttings

maximises surface area available for root powder to adhere to for roots to grow from

how does reducing leaves to two or four improve success rates of cuttings

reduces surface area so reduces transpiration rate, because cutting has no roots, water uptake is low so water loss must be minimised to keep the cutting alive, some leaves remain for photosynthesis

how does keeping the cutting well watered improve success rates of cuttings

due to cutting having no roots water uptake is low so water must be in plentiful supply to ensure the cutting gets enough water

how does covering the cutting with a plastic bag for a few days improve success rates of cuttings

traps water lost in transpiration, air around stomata is humid, lower water potential gradient from inside the leaf to outside across the stomata, less water lost by transpiration

what are some crops commonly propagated by cloning

bananas, sugar cane, sweet potato, cassava, coffee and tea bushes

define tissue culture

the method of growing plant cells, in isolation from the parent plant under sterile conditions in or on a nutrient culture medium of known composition

define micropropagation

the process of making large numbers of genetically identical offspring from a single parent plant using tissue culture techniques

define explant

the material removed from a parent plant for tissue culture

define callus

a mass of undifferentiated plant cells that has been grown from an explant

what is the technique for artificial cloning in plants called

micropropagation by tissue culture

what is the process of micropropagation by tissue culture

• cut plant into explants

• e.g. the meristem

• sterilise explants

• with bleach

• place on agar/growth medium in aseptic conditions

• containing glucose/amino acids

• callus forms

• high auxin and cytokinin for callus formation

• subdivide callus

• treat to induce roots/shoots

• change plant hormone ratio

• transfer to soil

why is micropropagation used when the desirable plant does not readily produce seeds

provides a way of growing plants which are relatively infertile or sexual reproduction is not feasible, or difficult to grow from seed

why is micropropagation used when the desirable plant foes not respond well to natural cloning

if cloning is required by natural cloning is not feasible then micropropagation is another way to clone plants

why is micropropagation used when the desirable plant is very rare

sexual reproduction may be unlikely if a different individual is needed to pollinate the plant, micropropagation is the best way to produce very large number of individuals very quickly

why is micropropagation used when the desirable plant has been genetically modified or selectively bred with difficulty

one cloning method is required so offspring are genetically identical to the desired plant, micropropagation can produce a very large number of new plants very quickly

why is micropropagation used when the desired plant is required to be pathogen-free

only a few cells are used to make each new plant, the method uses aseptic techniques, minimised likelihood of new plants carrying pathogens from the parent plant

what are some plants commonly propagated by micropropagation

potatoes, sugar cane, banana, strawberries, grapes, chrysanthemums, orchids, cassava

what are some advantages of micropropagation

• quick

• disease free stock created

• uniform plants created

• can reproduce infertile plants

• can reproduce plants that are hard to grow from seed

• can create whole plants from GM cells

• production at any time of year

• can be grown in small space/transported easily

• can save rare species from extinction

what are some disadvantages of micropropagation

• expensive/labour intensive process

• process can fail due to microbial contamination

• offspring susceptible to same pest/disease

• no genetic variation

what are some advantages of using vegetative propagation

• faster to get new individuals then by seed

• time to cropping is reduced than seed or micropropagation

• guaranteed quality of plants if clones taken from good stock- not necessarily the case in seed propagation

what are some disadvantages of artificial vegetative propagation

lacks genetic variation- may be a problem if new disease or pest appear, or climate change occurs

define a clone

a genetically identical copy of an original gene, cell or organism

define asexual reproduction

the generation of new individuals using mitosis to produce clones

define binary fission

the method of asexual reproduction in bacteria

define reproductive cloning

using cloning methods to produce 2 or more individuals that are clones of each other

what are natural cloning methods in animals

mitotic parthenogenesis, damage (e.g. starfish), monozygotic twinning, budding, fragmentation

what is mitotic parthenogenesis

a natural form of animal cloning, female animals produce eggs by mitosis not meiosis, eggs can then grow into clones of the mother

what is the name for natural animal cloning where the female produces eggs by mitosis not meiosis and the eggs then grow into clones of the mother

mitotic parthenogenesis

how does monozygotic twinning occur

one egg is fertilised by one sperm and one zygote is created, at some point the early embryo splits into two, each half grows into a new individual

what are ways of artificial cloning in animals

artificial twinning/embryo splitting, somatic cell nuclear transfer

how does embryo splitting work

1. gametes fuse to form zygote, gametes may be from G.M. parents or parents with desirable traits

2. embryo develops to the 16-cell stage

3. embryo is separated to individual cells

4. each cell now develops further into a separate and identical embryo

5. surrogate mothers have uterus made ready by hormonal treatment: increased vascularization and uterus wall thickness prepares for pregnancy

6. each embryo is implanted into a surrogate mother

7. surrogate mother carry cloned embryos to term

8. identical clones offspring born

9. embryos can be frozen so that one can be reared to adulthood to see what characteristics it has- if desirable then all other embryos can be used

how does somatic cell nuclear transfer work

1. egg donor super ovulated by hormones

2. remove nucleus of a somatic cell

3. fused with enucleated egg cell from another animal

4. electric shock stimulates division

5. embryo grows and divide in vitro

6. blastocyte is split

7. surrogate mothers uterus prepared by hormone treatment

8. embryos replaced in surrogate mothers

in splitting of embryos animal cloning what are the clones of

the zygote produced from sexual reproduction

in splitting of embryos animal cloning how strong is the ability to know the characteristics of the clones you are producing

limited due to sexual reproduction, and cloning before characteristics of animal become clear

in splitting of embryos animal cloning do mitochondria have different genetic material or are they true clones

true clones- have identical genetic material in mitochondria

in somatic cell nuclear transfer animal cloning what are the clones of

the animal that provided the somatic cell nucleus

in somatic cell nuclear transfer animal cloning how strong is the ability to know the characteristics of the clones

very strong, will be the same as the animal that provided the somatic cell, cn clone desired animals

in somatic cell nuclear transfer animal cloning do the mitochondria have different genetic material or are they true clones

different genetic material in mitochondria, nuclear genome is cloned

what are the advantages of animal cloning

• artificial twinning enables high yielding farm animals to produce many more offspring than normal

• animals giving high yields can be produced

• artificial twinning enables success of a male at passing on desirable genes

• desirable genetic characteristics will always be passed onto clones

• can prevent rare animals from going extinct

• infertile animals can be reproduced

• SCNT allows specific animals to be cloned

• SCNT allows GM embryos to be replicated and develop- many embryos from one engineering procedure, important in pharming

• SCNT could allow extinct animals to be reproduced

what are the disadvantages of animal cloning

• animals become genetically uniform- increasing susceptibility to disease

• animals may have low quality of life

• many animals have a shortened life span

• many cloned embryos fail to develop and miscarry, or produce malformed offspring

• undesirable characteristics passed onto clones

• reproductive cloning is difficult, time-consuming and expensive

• SCNT has been fairly unsuccessful in increasing populations or rare organisms/bringing back extinct species

• SCNT is inefficient- takes many eggs to produce a single cloned offspring

• work force must be highly trained which is expensive

what is non-reproductive cloning

production of new cells using mitosis for growth, repair and replacement

what is the technique for non-reproductive cloning

therapeutic cloning

what is the aim of therapeutic cloning

use non-reproductive cloning to produce cell, tissues or organs to replace those that are damaged

what are the advantages of non-reproductive cloning for use in therapeutic cloning

• no rejection by immune system

• no waiting for organ donors

• potential to generate any cell type- treat currently untreatable damage

• using cloned cells rather than whole organs requires less major surgery

steps in non-reproductive cloning

1. skin cells taken from patient, nuclear material extracted, cytoplasm discarded

2. unfertilized oocyte from female donor has nuclear material removed: enucleated

3. donor nucleus and enucleated oocyte are fused by the application of an electric current which causes the membranes to fuse

4. fused cell divides to form an embryo, develops to 150-cell stage- blastocyte

5. inner cell mass is removed from blastocyte and cultured in a petri dish with appropriate factors and growth medium

6. different developmental factors added to cause differentiation, cultured cells differentiate into appropriate cells that will be seeded back into patient’s tissue