3.2 Applications and skills

3.2.5 Clones and GMOs

  • Clones are genetically identical organisms, derived from a single original parent cell.
  • Cloning occurs naturally – species that reproduce asexually produce genetic clones in every generation (unless there is random mutation).
  • Many plant species and some animal species have natural methods of cloning.

Figure 3.2.5a – HydraFigure 3.2.5a – Hydra
Animals of the genus Hydra reproduce by budding. The bud is a genetic clone of its parent.

Figure 3.2.5b – Strawberry runnerFigure 3.2.5b – Strawberry runner
Strawberry plants send out horizontal stems called ‘runners’, that produce clones of the original plant.

Figure 3.2.5c – Bulb plantsFigure 3.2.5c – Bulb plants
Clones of bulb plants, including onions and tulips, grow from underground storage organs.

Skill: Investigating cloning in stem cuttings

  • Many plants can be cloned from cuttings. This is called vegetative propagation. New roots will grow within a few weeks of the stem cuttings being planted.

Figure 3.2.5d – How to cut stems to investigate vegetative propagationFigure 3.2.5d – How to cut stems to investigate vegetative propagation

  1. Remove leaves from the bottom of the young stem shoot.
  2. Cut below the node with a sharp, sterilised knife.
  3. Plant stem cuttings directly into soil or a nutrient medium (keeping them upright).
  • Consider all the environmental factors that might influence plant growth, such as humidity, light intensity, nutrients in the potting soil, depth of the pot, or anything else you can think of.
  • Design an investigation of one factor that affects rooting of stem cuttings. Determine which variables to control, and how to measure and analyse your results. Write a plan for your experiment.

Artificial cloning in animals

  • Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells. This process is called ‘artificial twinning’, or embryo splitting.

Figure 3.2.5e – Embryo splitting produces clonesFigure 3.2.5e – Embryo splitting produces clones

  • Embryo-splitting has been used to clone livestock animals after in vitro fertilisation (IVF).
  • Adult differentiated cells can also be used to clone animals in a process called somatic cell nuclear transfer.

Figure 3.2.5f – Somatic cell nuclear transfer, SCNT, was used to clone Dolly the sheepFigure 3.2.5f – Somatic cell nuclear transfer, SCNT, was used to clone Dolly the sheep

  • Dolly was the first successful clone produced using SCNT – in general cloning animals in this way is not feasible.
  • Instead, SCNT uses adult cells to produce cloned embryos that can act as a source of stem cells for therapies. 
screenshot

Figure 3.2.5f – SCNT in the production of cloned embryos using skin cells

Assessing risks of genetically modified organisms

  • A commonly grown GMO crop is corn that produces a pesticide. The pesticide-producing gene comes from a bacterium, called Bacillus thuringiensis, so this type of corn is called Bt corn.
  • A risk-benefit analysis for GMO crops may include investigations into the following claims:

Environmental factors

Agricultural factors

Benefit: Reduced need for large-scale spraying of chemical pesticides.

Benefit: Pest-resistant corn strains can increase yields.

Risk: The toxins produced by the corn may affect non-target pests like honeybees or butterflies.

Risk: Pests may become resistant to the toxin, leading to reduced yields in the long term.

Social factors

Health factors

Benefit: GMO crops allow high-yield varieties to flourish in poor soil conditions, so there is greater access to food worldwide. 

Benefit: Crops can be engineered for increased nutritional value.

Risk: Farmers are not allowed to re-sow patented seeds, and are forced into long-term relationships with large biotech corporations

Risk: Inserted genes may be high risk for mutation. Long-term effects on human health are unknown.

Figure 3.2.5g – Identical twinsFigure 3.2.5g – Identical twins
Identical twins are natural clones that form when one zygote splits into two embryos.

Figure 3.2.5h – Monozygotic twinsFigure 3.2.5h – Monozygotic twins
How embryos split into twins.

Food for thought

Do other mammals give birth to identical twins? What about reptiles or fish?

screenshotWatch the process of somatic cell nuclear transfer.

Science and social responsibility

Discuss the ethics of different genetic technologies. Where should the line be drawn between intellectual curiosity and the compassionate treatment of living organisms?

Figure 3.2.5i – MonsantoFigure 3.2.5i – Monsanto

Nature of Science

Assessing risks of research: How important is it that laboratory evidence is supported by field studies? Does it matter if research funding comes from inside the industry? How have stories in the press influenced your opinions on GMOs?

Figure 3.2.5j – Bt cornFigure 3.2.5j – Bt corn

Course link

Learn more about IVF in 6.2.6b.