3. Cloning In Animals

Question 1

Which animals can naturally clone?

Answer 1

Invertebrates

Less common in vertebrates- occurs in form of twinning

Question 2

Give examples of cloning in invertebrates

Answer 2

Starfish- regenerate entire animals from fragments of the original if damaged

Flatworms and sponges- fragment and form new identical animals= normal reproductive process

Hydra- small buds on side of body, develop into genetically identical clones

Some insects- female can produce offspring without mating

Question 3

How does cloning happen in vertebrates?

Answer 3

Monozygotic twins- identical twins
Embryo splits into 2
Unsure of trigger
Different frequencies in diff species- humans = 3/1000
Genetically identical, but may look diff due to diff positions in uterus and diff nutrition

Some female amphibians and reptiles= produce offspring when no males available, usually male, not clone of mother but all their genetic material arises form her
= parthenogenesis- fusion of females own gametes= more genetic diversity

Question 4

How do you produce artificial clones of sponges or starfish (some invertebrates)?

Answer 4

Liquidise sponges

Chop up starfish

Question 5

Why is artificial cloning used on animals?

Answer 5

Produce high-quality farm animals

Question 6

What are the 2 methods of artificially cloning vertebrates?

Answer 6

Artificial twinning

Somatic cell nuclear transfer

Question 7

What is artificial twinning?

Answer 7

Egg fertilised= divides forming ball of cells= totipotent for short time

Natural twinning= embryo splits naturally

Artificial twinning= embryo split is produced manually, may be split into number of pieces= number of identical offspring

Question 8

What is artificial twinning used for?

Answer 8

Farming

Produce max offspring from particularly good livestock

Embryos can be frozen

Question 9

What are the stages of artificial twinning in cattle?

Answer 9

Cow with desirable traits is treated with hormones so she super-ovulates= more mature ova released than normal

Ova fertilised naturally or by artificial insemination by bull with good traits

Day 6- cells are still totipotent, cells of early embryos split= several smaller embryos

Each grown in lab for few days to ensure healthy, then implanted into different surrogate mothers

Embryos develop into foetuses and are born genetically identical

Question 10

What is somatic cell nuclear transfer?

Answer 10

Cloning adult animal by taking nucleus from adult somatic (body) cell and transferring it to an enucleated egg cell (an oocyte which had nucleus removed)

Tiny electric shock used to fuse nucleus and egg, stimulate combined cell to divide and form embryo= clone of original adult

Question 11

Outline the process of somatic cell nuclear transfer

Answer 11

1. Nucleus removed from somatic cell of adult animal
2. Nucleus removed from mature ovum harvested from different female animal of the same species- it is enucleated
3. Nucleus placed into enucleated ovum, given mild electric shock so it fuses and begins to divide
   In some cases, nucleus not removed, placed next to ovum and the 2 cells fuse (electro fusion) and begin to divide under influence of the electric current
4. Embryo that developed is transferred into the uterus of a 3rd animal
   Embryo can be split to produce several identical clones
5. New animal= clone of original animal from. Which the somatic cell was taken, although the mitochondrial DNA will come from the egg cell

Question 12

What is somatic cell nuclear transfer also known as?

Answer 12

Reproductive cloning

As live animals are the end result

Question 13

Why is somatic cell nuclear transfer used?

Answer 13

Pharming- production of animals, genetically engineered to produce therapeutic human proteins in their milk

To produce genetically modified animals which grow organs that have potential to be used in human transplants

Question 14

What is a major issue with somatic cell nuclear transfer?

Answer 14

Premature aging

Dolly the sheep suffered with arthritis and diseases that typically only older sheep suffered with

Question 15

What are the arguments for animal cloning?

Answer 15

Somatic cell nuclear transfer= enable rare, endangered or extinct species to be reproduced
The nucleus from dried or frozen tissue could be transferred to the egg of a similar living species= clones of species that have been dead a long time

Artificial twinning= high-yielding farm animals to produce many more offspring than normal reproduction

Artificial twinning enables the success of a sire (male) at passing on desirable genes to be determined, if first cloned embryo= successful breeding animal, more can be produced

Somatic cell nuclear fusion enables scientists to clone specific animals- EG specific pets, top class race horses

Question 16

What are arguments against animal cloning?

Answer 16

Somatic cell nuclear fusion= insufficient, takes many eggs to produce single cloned offspring

Many cloned animal offspring fail to develop and miscarry or produce malformed offspring- ethics?

Many cloned animals have shortened life spans- EG dolly

Not time or money efficient

Somatic cell nuclear fusion= relatively unsuccessful in increasing pop of rare offspring or allowing extinct animals to be brought back to life
Shown by attempt to clone rare breeds of wild cattle