6.2.1 Cloning

Question 1

how can plants produce natural clones

Answer 1

vegetative propogation

Question 2

natural vegetative propagation: rhizomes

Answer 2

stem structures that grow horizontally underground away from the parent plant

have nodes from which new shoots and roots can develop

bamboo

Question 3

natural vegetative propagation: runners

Answer 3

grow horizontally above ground on the surface of the soil

new shoots and roots develop from nodes or form at the end of the stolon

strawberries

Question 4

natural vegetative propagation: sucker

Answer 4

shoots that grow from sucker buds (undeveloped shoots) present on the shallow roots of a parent plant

elm trees

Question 5

natural vegetative propagation: tubers

Answer 5

large underground plant structures that act as a food store for the plant

they’re covered in eyes - each eye is able to sprout and form a new plant

potatos

Question 6

natural vegetative propagation: bulbs

Answer 6

underground food stores used by some plants

new bulbs are able to develop from the original bulb and form new individual plants

onions

Question 7

production of natural clones in horticulture

Answer 7

cuttings

graftings ( joining shoot of one plant to the growing stem of another plant)

layering ( bending a stem of a growing plant downwards so it enters the soil and grows into a new plant)

Question 8

how do you produce a plant clone from cutting

Answer 8

1. use a scalpel to take a cutting, 5-10cm long, from the end stem of the parent plant
2. remove the leaves from the lower end of the cutting, leaving just one at the tip
3. dip the lower end of the cutting in rooting powders that contain hormones which induce root formation
4. then plant cutting in a pot with a suitable growth medium
5. provide cutting with a warm and moist environment (plastic bag or propagator)
6. when cutting has formed its own roots and is strong enough can plant it elsewhere

Question 9

how do you take a root cutting?

Answer 9

cut a piece of root with a straight cut using a scalpel
then remove the uncut end of the root with a slanted cut
dip the end in rooting powers and plant in a suitable growth medium

Question 10

how do you take a leaf cutting

Answer 10

remove a leaf
score the large veins on the lower leaf surface using a scalpel
then put it on top of the growth medium with broken veins facing down
a new plant should form from each break in the veins

Question 11

how are plants artificially cloned

Answer 11

tissue culture

Question 12

tissue culture technique

Answer 12

1. cells taken from the original plant - stem and root tip because they are stem cells
2. the cells are sterilised to kill any microorganisms - bacteria or fungi - that would compete for nutrients with the plant cells which decreases growth rate
3. the cells placed on a culture medium containing plant nutrients (eg glucose) and growth hormones (auxin)
4. when the cells have divided and grown into a small plant they are taken out of the medium and planted in soil —> develop into genetically identical plant to the original

Question 13

what is tissue culture used for?

Answer 13

to clone plants that don’t readily reproduce or are endangered or rare

to grow whole plants from genetically engineered plant cells

Question 14

what is micropropagation

Answer 14

when tissue culture is used to produce lots of cloned plants very quickly

cells taken from developing cloned plants and are subculture

repeating this process creates a large no. of clones

Question 15

what is micropropagation used for

Answer 15

used extensively in horticulture and agricultire

eg. to produce fields full of crop that has been genetically engineered to be pest-resistant

Question 16

arguments for artificial plant cloning

Answer 16

1. desirable characteristics arent always passed on when plants reproduce sexually
2. tissue culture allows plants to be reproduced in any season because the environment is controlled
3. less space is required by tissue culture than would be needed to produce the same number of plants by conventional growing methods
4. it produces lots of plants quickly compared to the time it would take to grow them from seeds

Question 17

arguments against artificial plant cloning

Answer 17

1. undesirable genetic characteristics are always passed onto clones
2. cloned plant populations have no genetic variability, so a single disease could kill them all
3. production costs of tissue culture are very high due to energy use and the training of skilled workers, so its unsuitable for small-scale production
4. contamination by microorganisms during tissue culture can be disastrous and result in complete loss of the plants being cultured

Question 18

nature animal clones

Answer 18

identical twins
- in very early stages of development possible for embryo to split and develop into multiple embryos with the same genetic information

Question 19

artificial animal clones - two types

Answer 19

artificial embryo twinning

somatic cell nuclear transfer (SCNT)

Question 20

artificial animal clones - artificial embryo twinnig

Answer 20

1. an egg cell is extracted from a female cow and insterted and fertilised in a petri dish
2. the fertilised egg is left to divide at least once, forming an embryo in vitro
3. the individual cells from the embryo are separated and each is put in a separate dish
   - each cell divides and develops normally so an embryo forms in each petri dish
4. the embryos are then implanted into female cows (surrogate mother)
5. the embryos continue to develop inside the surrogate cows and eventually offspring are born
   - they are all identical to each other

Question 21

artificial animal clones - somatic cell nuclear transfer

Answer 21

1. a somatic cell is taken from sheep A - the nucleus is extracted
2. an oocyte ( immature egg cell ) is taken from sheep B - its nucleus is removed - forming an enucleated oocyte
3. the nucleus from sheep A is inserted into the enucleated oocyte - the oocyte from sheep B now contains the genetic information of sheep A
4. they are fused together and stimulated to divide by electrofusion - this produces an embryo
5. then the embryo is implanted into a surrogate mother and eventually, a lamb is born that is a clone of sheep A

Question 22

uses of animal cloning

Answer 22

1. research - test new drugs (variables from genetic differences removed)
2. save endangered animals from extinction
3. used in agriculture to increase the number of animals with desirable characteristics to breed from
   - eg. high milk yield
4. animals that have been genetically modified to produce a useful substance that they wouldn’t normally produce (eg beneficial protein in milk) could be cloned to produce lots of identical animals that all produce the same substance
5. could harvest the young embryos that have the potential to become any cell type - to be used to replace damaged tissues in a range of diseases

Question 23

arguments for animal cloning

Answer 23

1. desirable genetic characteristics are always passed onto clones which doesn’t always happen in sexual production
2. infertile animals can be reproduced
3. increasing the population of endangered species helps preserve biodiversity
4. animals can be cloned at any time - don’t have to wait until a breeding season
5. cloning can help us develop new treatments for disease, which could mean less suffering for some people

Question 24

arguments against animal cloning

Answer 24

1. difficult, time-consuming and expensive
2. no genetic variability, so undesirable characteristics always passed on. so all the cloned animals in a population are susceptible to the same diseases (a single disease could wipe them out)
3. some evidence shows that clones may not live as long as natural off spring - some think this in unethical
4. using cloned human embryos as a source of stem cells is controversial - embryos usually destroyed after the embryonic stem cells have been harvested - some people believe that this is destroying a human life