22.3 Cloning in Animals

Question 1

How does cloning occur in invertebrates?

Answer 1

buds on side of body

form clones which are independent

Question 2

How does cloning occur in vertebrates?

Answer 2

formation of monozygotic twins

early embryo splits, forming 2 independent embryos

Question 3

What are the 2 types of animal cloning?

Answer 3

artificial twinning

somatic cell nuclear transfer (SCNT)

Question 4

What is artificial twinning?

Answer 4

process of producing monozygotic twins

artificially

Question 5

Outline the stages of artificial twinning:

Answer 5

1. cow with desirable traits treated with hormones
   
   1. causes release of more egg cells than normal
2. Fertilised (naturally/artificial insemination/removed & fertilised in lab) by bull with good traits
3. before blastocyst forms, while cells are still totipotent, embryo triggered to split
4. Embryos implanted into surrogate mothers
5. embryos develop & are clones due to derived from same embryo

Question 6

Why may artificial twinning be used?

Answer 6

produce much larger numbers

of clones with genetically desirable traits

than possible with natural reproduction

Question 7

What is somatic cell nuclear transfer?

Answer 7

method of producing a clone

from an adult animal

by transferring the nucleus from a somatic cell

to an enucleated egg cell

& stimulating development

Question 8

Outline the process of SCNT, somatic cell nuclear transfer:

Answer 8

1. Nucleus removed from somatic cell of adult animal
2. Egg cell harvested from female of same species, nucleus is removed
3. Nucleus from adult somatic cell transferred ⟶ enucleated egg cell
4. Mild electric shock triggers cell division
5. Embryo transferred into surrogate mother
6. develops into clone of adult animal from which somatic cell had nucleus removed, however mtDNA comes from egg cell

Question 9

What are the advantages and disadvantages of animal cloning?

Answer 9

• ADVANTAGES
  
  • Artificial twinning allows livestock to produce more offspring than normal
  • SCNT allows cloning of specific animals
  • Allows proliferation of endangered species
• DISADVANTAGES
  
  • SCNT is inefficient, ∵ requires many eggs due to low success rate
  • Many cloned embryos fail to develop
  • Cloned animals have shorter lifespans & may be more susceptible to some conditions
  • Ethical concerns