22 - Cloning And Biotechnology (6.2.1 A-D)

Question 1

What is CLONING?

Answer 1

Producing offspring genetically identical to the parent organism and each other through mitosis

Question 2

What are MONOZYGOTIC TWINS?

Answer 2

Identical twins

Question 3

What is the definition of TOTIPOTENT?

Answer 3

The potential of a cell to form an entirely new animal

Question 4

What is ARTIFICIAL TWINNING?

Answer 4

Splitting an early embryo manually to form two foetuses

Question 5

What is SOMATIC CELL NUCLEAR TRANSFER?

Answer 5

The transferring of a nucleus from an adult somatic cell to an enucleated oocyte

Question 6

What is MICROPROPAGATION?

Answer 6

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

Question 7

What is TISSUE CULTURE?

Answer 7

The growth of tissues or cells in an artificial medium taken from tissues of a sample plant

Question 8

What is an enucleated oocyte?

Answer 8

An egg cell with its nucleus removed

Question 9

How can a plant cutting be used to make a simple clone?

Answer 9

1. Extract a small sample of the plant tissue you want to clone (e.g. meristem) under sterile conditions.
2. Sterilise the sample by immersing it in sterilising agents (bleach, ethanol or sodium dichloroisocyanurate).
3. Mitosis is stimulated by placing the explant in a sterile culture medium containing a balance of plant hormones (including auxins and cytokinins)
4. Proliferation (multiplication) occurs and the cells form a callus.
5. Individual cells or clumps from the callus are divided up then transferred to a new culture medium with a different mixture of hormones and nutrients.
6. Genetically identical plantlets develop.
7. Compost is used to pot the plantlets where they grow into small plants.
8. Crop production occurs when the young plants are planted out to grow.

Question 10

What is the material removed from the plant after sterilisation called?

Answer 10

Explant

Question 11

Which sterilising agent does not need to be washed off and therefore allows the plant tissue to remain sterile for longer?

Answer 11

Sodium dichloroisocyanurate

Question 12

What is a ‘callus’?

Answer 12

A mass of identical cells

Question 13

What are the benefits of micropropagation (artificially cloning plants)?

Answer 13

Rapid production of large numbers of plants with KNOWN GENETIC MAKEUP which will yield good crops.

Culturing meristem tissue produces disease-free plants.

Seedless new plants that are sterile to meet consumer tastes can be produced in large numbers.

Naturally relatively infertile plants / difficult to grow from seed can be grown (like orchids).

Possible to produce viable numbers of plants after the genetic modification of plant cells.

Question 14

What are the cons of micropropagation (artificially cloning plants)?

Answer 14

Monoculture makes plants susceptible to the same diseases and changes in growing conditions.

Expensive process and requires skilled workers.

Explants and plantlets are vulnerable to infection by moulds and other diseases during the production process.

Infection of all of the clones if the source material is infected with a virus

Large numbers of new plants are lost during the process

Question 15

In which two ways can clones be produced in animals?

Answer 15

Artificial twinning and somatic cell nuclear transfer (SCNT)

Question 16

How does artificial twinning produce a clone?

Answer 16

1. Cow with desirable traits is treated with hormones to super-ovulate, releasing more mature ova than normal.
2. Ova is fertilised naturally / artificial insemination / in vitro fertilisation by a bull with good traits.
3. Early embryos are gently flushed out of uterus.
4. Embryo cells are still totipotent around Day 6 and are split to produce several smaller embryos.
5. Split embryos are grown in a lab for a few days to ensure all is well.
6. Different surrogate mothers are implanted with each embryo as single pregnancies have less risks.
7. Foetuses form and are born normally.

Question 17

How does somatic cell nuclear transfer produce a clone?

Answer 17

1. Nucleus removed from a somatic cell of an adult animal.
2. Mature ovum harvested from different female animal of same species is enucleated.
3. Adult somatic cell’s nucleus is placed into the enucleated ovum.
4. Electrofusion occurs as the influence of the electric current causes fusion and cell division.
5. Embryo transferred into uterus of a third animal.
6. New animal is a clone of the animal the somatic cell came from.
7. THE MITOCHONDRIAL DNA COMES FROM THE EGG CELL.

Question 18

How is somatic cell nuclear transfer different to artificial twinning?

Answer 18

Artificial twinning clones an embryo while somatic cell nuclear transfer clones an adult animal.

Question 19

What are the arguments for animal cloning?

Answer 19

Artificial twinning enables high-yielding farm animals to produce more offspring than normal.

Specific animals can be cloned with SCNT (like pets or race horses).

Potential to enable rare, endangered or extinct animals to be reproduced as their dry nuclei can be used.

Helps determine the success of a sire (male animal) at passing on desirable traits, as more identical animals can be reared if the first cloned embryo results in a successful breeding animal.

SCNT is an important process in ‘pharming’ — the production of therapeutic human proteins in the milk of GM farm animals.

Question 20

What is pharming?

Answer 20

The production of therapeutic human proteins in the milk of GM farm animals.

Question 21

What are the arguments against cloning animals?

Answer 21

Very inefficient process as it takes many eggs to produce a single cloned offspring.

Many cloned embryos fail to develop and miscarry or produce malformed offspring.

Shortened lifespans are prevalent in cloned animals.

Unsuccessful so far in increasing the populations of rare or extinct species.