Chapter 22 Cloning

Question 1

What is asexual reproduction?

Answer 1

A type of cloning using mitosis, so only one parent is needed
Identical genome to the parent

Question 2

What is a clone?

Answer 2

An organism which is genetically identical to the parent

Question 3

What is vegetative propagation / natural cloning?

Answer 3

A structure which has formed from a plant that can develop into a fully differentiation new plant, identical to that of the parent

Question 4

What are examples of natural cloning in plants?

Answer 4

Bulbs- like seeds
Runners- lateral stems which can grow new roots and separate
Rhizomes- a horizontal underground stem
Tubers- like baby potato’s

Question 5

Why might / might not farmers use natural cloning?

Answer 5

Able to cut sections of stems/ runners and able to grow the plant quickly
Guarantees quality of the plant- state a property e.g large, round

But less variation so all plants susceptible to the same thing

Question 6

Why might a plant be cloned via micropropagation?

Answer 6

When seeds are not produced rapidly
Cannot undergo natural cloning
When the species is rare
When growth must be pathogen free

Question 7

What is the process of plant cloning via micropropagation?

Answer 7

1. Take a small sample of the plant tissue- it must be meristematic so shoot tips and buds often
2. Sterilise with ethanol or bleach, this doesn’t need to be rinsed off.
3. Place the sample into sterile culture medium containing plant hormones which stimulate mitosis. A callus is formed
4. The callus is divided into small clumps and transferred to new culture medium, where it is stimulated by hormones to grow into plantlets.
5. Place the plantlets in compost and they will grow

Question 8

What is the explant? What is the callus?

Answer 8

Explant- plant material after it has been sterilised
Callus- Mass of identical cells formed during first culture medium

Question 9

What are the advantages of micropropagation?

Answer 9

Rapid production of good crops
Disease free crops
Seedless fruit
Can grow infertile plants
Useful for cloning rare plants

Question 10

What are the disadvantages of micropropagation?

Answer 10

Monoculture, meaning more susceptible to changes in the environment
Expensive
Requires skilled workers
If viruses are present in product, goes to all clones
Plants can be lost in the process

Question 11

What are examples of natural cloning in invertebrates?

Answer 11

Starfish- regrow from both sections when cut
Flatworms and sponges grow from fragments
Some females reproduce without mating e.g bees

Question 12

What are examples of natural cloning in vertebrates?

Answer 12

Monozygotic twins- identical to each other
Embryo splits into 2, unknown why, and frequency differs between species

Question 13

What are the two types of artificial cloning in vertebrates?

Answer 13

Artificial twinning
Somatic Cell Nuclear Transfer (SCNT)

Question 14

How is artificial twinning carried out in cows?

Answer 14

A cow with desirable characteristics is chosen. They are subjected with hormones to increase ovulation and release more mature ova
The ova is fertilised either naturally or artificially from a bull with desirable characteristics
The early embryos are flushed out gently
Before day 6, the cells are totipotent , and so are split into several smaller embryos
Each embryos is grown in the lab to ensure they develop correctly, and then placed into separate mothers, where they are delivered naturally

(Pigs naturally give birth to triplets so need more multiple embryos inserted)

Question 15

What is the process of SCNT?

Answer 15

The nucleus from a somatic cell of an adult is removed
The nucleus from a mature ovum is also remove
The nucleus from desired cell is place into the enucleated ovum using a needle/micropipette, and a mild electric shock is given to cause fusion and division,
(Sometimes the nucleus of the desired is not removed and the cells fuse via electro fusion)
The embryo is transferred to the uterus of a third animal and it develops and is born

Question 16

Are the clones of SCNT true clones?

Answer 16

No the mitochondrial DNA is from the ovum, so they are not identical

Question 17

Why did dolly the sheep die young?

Answer 17

The ends of chromosomes are called telomeres, they have been known as the mitotic clock and shorten with age
As the nucleus of dolly came from an adult, they were shortened and so her life was shorter as the cells were effectively older
If there was a way to repair the telomeres, dolly could have lived a normal life

Question 18

What are the advantages of using animal cloning?

Answer 18

High yielding animals are guaranteed
Genetically modified organisms can be cloned so modifications move through
Mass production- can be frozen and used if the cloned organisms is successful
Helps with rare animals or those than cannot breed well

Question 19

What are the disadvantages of cloning animals?

Answer 19

Inefficient as many eggs are needed for 1 successful clone
Many embryos do not develop, miscarry, or produce malformed offspring
Shortened lifespans common
Difficult to bring animals from the past back to life with this

Question 20

Why have humans not been cloned yet?

Answer 20

Spindle fibres are very close to the nucleus
Removing the nucleus often damaged the spindle fibres so the cell cannot divide

Question 21

Why can plants naturally clone themselves more easily than humans?

Answer 21

Contain lots of meristematic tissue with totipotent stem cells
Cells can dedifferentiate and then divide

Human specialised cells cannot undergo mitosis, multipotent limited stem cells within some tissues, not enough for cloning

Question 22

How do you define cloning?

Answer 22

Producing genetically identical copies of an individual, cell, or gene

Question 23

How do the equipment and techniques of cuttings and micropropagation differ?

Answer 23

Cuttings need less expensive equipment, sterile equipment and rooting powder, no petri dishes
Micropropagation requires more skill staff, and greater care to ensure aseptic technique is carried out
Micropropagation will produce more offspring from one sample

Question 24

How do you take a cutting from a plant?

Answer 24

Cut a shoot from a healthy plant, at an angle and using sterile equipment
Or cut between nodes
Place in rooting powder, contains auxin
Place in soil and add water

Question 25

Why can micropropagation produce many clones from one plant?

Answer 25

Multiple explants can be taken
Each bundle of cells, callus, can be subdivided
Each plantlet can be subdivided

Question 26

What does in vitro mean? And ex vitro?

Answer 26

In- within glass, so any test-tube reactions
Ex- anything not in glass, can be inside an organism

Question 27

Why are clones used within medical testing?

Answer 27

All have the same genome, genetically identical
Removes genetic variation as a factor such could affect the disease, results are purely based on the treatment
More valid comparison