6.4.3 aritifical clones in animals

Question 1

define embryo twinning

Answer 1

splitting an embryo to create 2 genetically identical embryos

Question 2

define enucleation

Answer 2

removal of cell nucleus

Question 3

define somatic cell nuclear transfusion (SCNT)

Answer 3

technique involving transferring the nucleus from somatic cell to an egg cell

Question 4

what does the cell need to be to start cloning

Answer 4

totipotent = divide & differentiate into all cell types found in adult organism

Question 5

what might reproductive cloning be useful for

Answer 5

• elite farm animals produced by selective breeding (artificial selection) or genetic modification
• genetically-modified animals developed with unusual characteristics

Question 6

2 main techniques to achieve reproductive cloning

Answer 6

1. embryo twinning/splitting
2. somatic cell nuclear transfer (SCNT)

Question 7

describe the process of embryo splitting

Answer 7

1. zygote is created by in vitro fertilisation (IVF)
2. zygote allowed to divide by mitosis to form small ball of cells
3. cells are separated & allowed to continue dividing
4. each small mass of cells is placed until uterus of surrogate mother

Question 8

what is embryo splitting used for

Answer 8

clone elite farm animals or animals for scientific research

Question 9

what does the genotype/phenotype of the offspring produced by embryo splitting determined by

Answer 9

egg & sperm used

Question 10

advantage of SCNT

Answer 10

phenotype is known before cloning starts

Question 11

describe the process of SCNT

Answer 11

1. an egg cell is obtained & it’s nucleus is removed = enucleation
2. normal body cell (somatic cell) from adult being cloned is isolated & may have nucleus removed
3. complete adult somatic cell (or it’s nucleus) is fused with empty egg cell by applying electric shock (electrofusion)
4. shock also triggers egg cell to start developing, as has just been fertilised
5. cell undergoes mitosis producing small batch of cells
6. young embryo placed into uterus of surrogate mother

Question 12

what is therapeutic cloning

Answer 12

(non-reproductive cloning) new tissues & organs can be grown as replacement parts of people who aren’t well

Question 13

examples of therapeutic cloning

Answer 13

• skin can be grown in vitro to act as graft over burned areas
• cloned cells have been used to repair damage to spinal cord of mouse & restore capability to produce insulin in pancreas
• potential to grow whole new organs to replace diseased organs

Question 14

arguments for artificial cloning in animals

Answer 14

• can produce whole herd of animals with high yield or showing unusual combination of characteristics
• produces genetically identical copies of high value individuals who retain same characteristics
• using genetically identical embryos & tissues for scientific research allows effects of genes/hormones be assessed without interference from different genotypes
• testing medicinal drugs on cloned cells/tissues avoids animal testing
• can produce cells/tissues genetically identical to donor, for use in repairing damage by disease/accidents
• individuals from endangered species can be cloned to increase numbers

Question 15

arguments against animal cloning

Answer 15

• lack of genetic variation may expose herd to diseases/pests & animals may be produced with little regard to their welfare which could have undesirable effects
• success rate of adult cell cloning is poor & method is more expensive than conventional breeding so cloned animals may be less healthy & have shorter life spans
• ethical issues regarding how long embryo survives & whether its right to destroy it
• cloning individuals from endangered species & increasing numbers doesn’t increase genetic diversity