6.2.1a-d Cloning

Question 1

Define clone

Answer 1

offspring produced by mitosis
- genetically identical to parent organism

Question 2

Define Asexual reproduction

Answer 2

• generation of new individuals
  -often naturally using mitosis to produce clone

Question 3

Define Reproductive cloning

Answer 3

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

Question 4

Define Vegetative propagation

Answer 4

the production of plant clones from non-reproductive tissues (natural cloning)

Question 5

Define perennating organ

Answer 5

plant structures which allow them to survive adverse contitions.
- contain stored food and can remain dormant in the soil

Question 6

What is the link between perennating organs and vegetative propagation?

Answer 6

Vegetative propagation takes place from perennating organs after adverse conditions when they stop being dormant and the stores of food are used to grow new planta from the organ

Question 7

What are 4 ways in which plants naturally clone (vegetative propagation) ?

Answer 7

1- bulbs - swollen,tightly packed underground leaves
2- runners - horizontal, above ground stems
3- rhizomes - horizontal underground stems
4- stem tubers - swollen, underground stems

Question 8

Define horticulture

Answer 8

branch of agriculture dealing with just plants

Question 9

Define agriculture

Answer 9

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

Question 10

How is the production of natural clones exploited in horticulture by farmers and gardeners? and why?

Answer 10

to produce new plants
- by splitting up bulbs
- removing young plants from runners
- cutting up rhizomes
–to increase plant numbers cheaply
– all new plants have same genetic characterstics as parents - known and favoured ones

Question 11

Define ‘taking cuttings’ and how the process is used in horticulture

Answer 11

• removing and planting short sections of stem of a plant to produce clones of that plant
• used to increase plant numbers (quicker than growing from seed) - all clones of parents - good stock

Question 12

What are 6 ways to increase the success rate of taking cuttings?

Answer 12

1- use a non flowering stem - resources arent needed to maintain flowers cells so used to grow roots
2- make 45degree cut in stem between nodes - larger SA for roots to grow from
3- use hormone rooting powder - encourage growth of new roots
4 - reduce leaves to 2 or 4 - reduces SA so reduces transpiration rate as water uptake very low until new roots well developed
5- keep cuttings well watered- will die if not watered and needs to establish roots before it can draw enough up itself
6- cover the cutting with a plastic bag for a few days - humid
- reduces loss of water while new roots establish

Question 13

Give 5 examples of crops that are propagated by cloning

Answer 13

• sugar cane - bananas - sweet potatoes - cassava - tea - coffee

Question 14

What are advantages of propagating crops by cloning?

Answer 14

• large numbers of new plants especially of sterile plants such as seedless grapes (please consumers)
• reliably increasing numbers of rare plants and/or plants difficult to grow from seed
• allow stocks to be built up quickly
• known genetic profile - produce good quality crops
• uniform plants make harvesting easier + produced quality crops

Question 15

What are disadvantages of propagating crops by cloning

Answer 15

• produces a monoculture - all plants susceptible to same diseases /changes in growing conditions
• labour intensive
• pathogens can be passed from parents

Question 16

Draw a table to compare production of new individuals by seed with producing new individuals by taking cuttings

Answer 16

SEED:
-Genetically diverse
-long growing time
-Low cost
-need to maximise pollination and provide ideal requirements for germination and seedling growth
-favoured when low cost and genetic variety important
- problems occur when plants difficult to grow from seed e.g. orchids or when sexual reproduction is unreliable
- occurs naturally so no need for human intervention
-dependent on seasons

CUTTINGS:
-Clones of parents
-short growing time
- high cost/labour requirements
- need to use non flowering stems and rooting hormone with plenty of watering
-favoured when need good crop quickly and when plant has a high success rate for cuttings or clones are wanted
- problems occur as are susceptible to drying out
- pathogens can be transferred
- there is guaranteed quality
- monoculture is a problem

Question 17

Define tissue culture

Answer 17

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

Question 18

Define micropropagation

Answer 18

growing large numbers of new genetically identical offspring from a single parent plant using tissue culture technique

Question 19

Is micropropagation artificial or natural plant cloning technique

Answer 19

artificial plant cloning

Question 20

Define explant

Answer 20

material removed from a parent plant for tissue culture

Question 21

Define callus

Answer 21

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

Question 22

Describe 5 reasons why micropropagation might be used to clone plants

Answer 22

1- desirable plant doesnt readily produce seeds
2- desirable plant doesnt respond well to natural cloning
3- desirable plant is very rare
4-desirable plant has been genetically modified or selectively bred with difficulty
5- desired plant is required to be pathogen free - grown in sterile conditions and original explant is sterilised

Question 22

Why is artifical plant cloning easy?

Answer 22

because the meristems in plants are totipotent - can diffrentiate into all cell types

Question 23

Describe the proceess of micropropagation by callus tissue culture

Answer 23

done in sterile conditions to avoid contamination
1 - take small sample of tissue from plant - meristem tissue from shoot tips/axial buds
2 - explant (material removed from parent plant for tissue culture) is sterilised (w/ bleach/ethanol)
3- transfer to sterile agar/culture medium
4- culture medium containing hormones to stimulate mitosis
5 - cells multiply rapidly by mitosis forming callus (mass of identical cells)
6- callus divided up and individual cells/clumps transferred to new medium stimulating growth of plantlets
7- plantlets potted into compost growing into small plants

Question 24

Give 9 examples of plants that are commonly produced by micropropagation

Answer 24

• potatoes - sugar cane - bananas - cassava - strawberries - grapes - orchids

Question 25

What are the arguments for micropropagation?

Answer 25

• can grow plants that are naturally infertile/rare/endangered
• produce large numbers of genetically modified plants
• can produce large numbers of seedless for consumer taste
• known genetic makeup - yield good crops
• rapid
• disease free plants
• any season - done indoors

Question 26

What are arguments against micropropagation?

Answer 26

• produces monoculture - genetically identical - suseceptible to same diseases/changes in growing conditions
• expensive
• labour intensive
• conditions have to be sterile - aseptic conditons
• if source material infected with virus - all clones also infected
• large numbers of plants can be lost
• explants and plantlets - vulnerable to infection by moulds+other diseases during production

Question 27

What is an example of natural animal cloning?

Answer 27

identical twins (monozygotic twins)

Question 28

What are the 2 ways of artificially cloning animals?

Answer 28

embryo splitting and somatic cell nuclear transfer (SCNT)

Question 29

Describe 5 examples of natural cloning in animals

Answer 29

1- mitotic parthenogensis - development of an embryo from an unfertilised egg formed by mitosis rather than meiosis so has full number of chromosomes
2- damage - animal damage - multiple pieces develop into new organisms
3- monozygotic twinning - 1 zygote splits and forms 2 embroys
4- budding - new organism develops from an outgrowth/bud due to cell division at a particular site - attatched until mature
5- fragmentation - organism splits into fragments which develop into mature fully grown individuals

Question 30

How in some species can offspring be produced without a male - but they are not clones?

Answer 30

Parthenogenesis- (embroyo develops from an unfertilised egg)
- an egg is ‘fertilised’ by another egg or similar gamete both from mother
- bc of different alleles and random assortment and crossing over in meiosis which created the egg, the offspring although gentically similar will not be clones

Question 31

Define monozygotic

Answer 31

• identical twins formed from single fertilised egg

Question 32

How do indentical twins occur?

Answer 32

• when 1 egg is fertilised by 1 sperm and 1 zygote (fertilised egg) forms
• early embryo splits into 2 and each half grows into new individual

Question 33

What are the 2 way a of artificially cloning animals

Answer 33

-Embryo splitting
- Somatic Cell Nuclear Transfer (SCNT)

Question 34

Describe the process of cloning animals by embryo splitting?

Answer 34

1 - gametes fuse to form zygote (in vitro fertilisation)
2- embryo develops to 16-cell stage
3- embryo is seperated to individual cells
4- each seperated cell develops further into a seprate and identical embryo
5- surrogate mothers have uterus made ready by hormonal treatment: increased vascularisation, uterus thickness prepares for pregnancy
6- each embryo is implanted into a surrogate mother
7- surrogate mothers carry cloned embryos to term.
8- identical cloned offspring born

Question 35

Describe the process of cloning animals by somatic cell nuclear transfer

Answer 35

1- obtain a somatic (body) cell of an adult animal
2- remove the nucleus from a somatic cell of an adult cell -(get rid of cell membrane)
3- from a female - remove the nucleus of an egg cell - enucleated
4- place the nucleus from the adult somatic cell into the nucleated egg cell and fuse via electric shock
5- fused cell begins to divide into an embryo
6- developed embryo transferred into uterus of surrogate mother
7- new animal is clone of animal of where somatic cell is derived even though mitochondrial DNA from animal providing egg cell

Question 36

what is a somatic cell?

Answer 36

any body cell - (any cell that isn’t a sex cell)

Question 37

What are the arguments for animal cloning?

Answer 37

• artificial twining enables high yielding farm animals to produce many more offspring than normal reproduction
• guarantees success of passing on desired characteristics
• if used to prevent rare animals from going extinct will prevent loss of genes/alleles from species
• infertile animals can be reproduced
• SCNT allows scientists to clone specific animals - pets/racehorses
• SCNT allows GM embryos to be replicated + develop - give many embryos from 1 engineering procedure
• SCNT can enable rare/endangered/extinct animals to be reproduced

Question 38

What are the arguments against animal cloning?

Answer 38

• animals become genetically uniform - increase disease susceptibility
• animals may have low quality of life/shortened life span
• many cloned embryos fail to develop and miscarry or produce malformed offspring
• not only desirable characteristics are passed onto clones
• difficult
• time consuming
• expensive
• SCNT unsuccessful so far in helping endangered/extinct animals
• SCNT very inefficient - in most animals it takes many eggs to produce a single cloned offspring
• work force must be highly trained - expensive labour