Stem Cells and Cloning Study Guide

Complete the following on additional sheets of paper.

U1.1.4 Multicellular organisms have properties that emerge due to the interaction of their cellular components.

1. Define and give examples of emergent properties.

Emergent properties arise from the interaction of the component parts of a structure.

Heart cell – characteristics of life Heart tissue – can synchronize contractions Heart organ – can pump blood Cardiovascular system – can deliver blood

throughout the body Organism – can use blood for interconnected

functions

U1.1.5 Specialized tissues can develop by cell differentiation in multicellular organisms.

2. Define tissue:

A group of cells that specialize in the same way to perform the same function.

3. Outline the benefits of cell specialization in a multicellular organism.

Cells can be more efficient in their role. They can have a specialized structure and metabolism.

4. Define differentiation:

Development of specialized structures and functions in cells.

U1.1.6 Differentiation involves the expression of some genes and not others in a cell.

5. Describe the relationship between cell differentiation and gene expression.

Differentiation in cells is due to different cell types. All cells in a multicellular organism contain the same genes, but different cells will express different genes. To express a gene means to “switch it on” so that the protein (or other gene product) is made.

U1.1.7 The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.

6. Define zygote and embryo

Zygote – the cell that results from a sperm fertilizing an egg cell.

Embryo: early stages of development after the zygote divides.

7. List 2 key properties of stem cells.

Stem cells can divide repeatedly: useful for treatment of tissues that need to replace cells that have been killed or damaged.

Stem cells are not differentiated: they haven’t “turned off” genes so they can still differentiate to produce different cell types.

8. Explain why stem cells are most prevalent in early embryonic development.

The cells of the early embryo are the most versatile. As the embryo develops, the cells gradually become more differentiated.

9. Contrast the characteristics of embryonic, umbilical and adult somatic stem cells.

Embryonic: can differentiate into any body cell (pluripotent)

Umbilical: can only differentiate into blood cells (multipotent)

Adult Somatic: found in bone marrow, skin and liver; limited differentiation ability (multipotent)

10. Define totipotent, multipotent, and pluripotent.

Totipotent: can become any body cell plus placenta. Zygote is totipotent

Pluripotent: Can become any body cell (but not placenta). Blastocyst ICM is pluripotent.

Multipotent: have partially differentiated but can still become multiple, related cell types (umbilical cord stem cells and adult stem cells),

A1.1.3 Use of stem cells to treat Stargardt’s disease and one other named condition.

11. Outline the cause and symptoms of Stargardt’s disease.

Stargardt’s disease is a recessive genetic disease. Light detection cells of the retina degenerate so vision becomes progressively worse.

12. Explain how stem cells are used in the treatment of Stargardt’s disease.

Retina cells derived from embryonic stem cells are injected into the eyes. The cells attach to the retina and improve vision without harmful side effects.

13. Outline the cause and symptoms of leukemia.

Leukemia is a cancer that results from an accumulation of mutations leading to uncontrolled division of the cells that create white blood cells.

14. Explain how stem cells are used in the treatment of leukemia.

The person with leukemia is given chemotherapy, which kills the cancer cells. Then, bone marrow (with its adult stem cells) is transplanted from a donor to the person with leukemia. The stem cells establish themselves, divide, and start to produce blood cells.

Ideally, the stem cells from the person with cancer can be harvested before chemotherapy and then returned to their body.

A1.1.4 Ethics of therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a newborn baby and from an adult’s own tissues.

15. List the source and mechanisms of obtaining stem cells.

Embryonic: removed from a blastocyst inner cell mass.

Cord blood: easily obtained from the umbilical cord.

Adult: buried deep in tissues, difficult to obtain.

16. Discuss the benefits and drawbacks of using stem cells from different sources.

Embryonic:

Unlimited growth and differentiation potential

Cells won’t have genetic mutations that accumulate with age.

Risk of becoming tumorous

Kills embryo

Cord blood:

Easy to obtain and store

Compatible with the adult that grows from the baby (no immune rejection)

Multipotent, so limited cell types can be created

Adult:

Full compatible with adult donor, so no risk of immune rejection

Hard to obtain in the body

Multipotent, so limited cell types can be created

Don’t have to kill embryo

NOS 1.1.2 Ethical implications of research – research involving stem cells is growing in importance and raises ethical issues.

17. Explain why biological research must take ethical issues into consideration.

Biological research is a human endeavor and as such will lead to people having different opinions about what is ethical and should be permitted. The opinions must be considered while deciding what is best for the collective good.

U3.5.5 Clones are groups of genetically identified organisms derived from a single original parent cell.

18. Contrast sexual and asexual reproduction.

Sexual reproduction: offspring are genetically different from the parents. Involves the fusion of a male and female gamete.

Asexual reproduction: offspring are genetically identical to the parent

19. Define clone and cloning:

Clone: a genetically identical organism

Cloning: the production of a clone

20. Describe different ways in which natural clones can arise.

Zygote divides into two cells, each developing into an embryo.

Embryo Splitting Fission Budding

U3.5.7 Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells.

21. Describe the process of reproductive cloning via embryo splitting.

A pluripotent embryo (usually at the 8 cell stage) is separated into separate cells which can each develop into separate indviduals.

22. Outline examples of cloning animal embryos via natural & artificial embryo splitting.

In nature, embryo splitting results in identical twins

Artificially, can be performed in livestock embryos (cows). But, rarely done. Use a squirt of saline solution or a special micro-scale scalpel to split the embryo.

U3.5.8 Methods have been developed for cloning adult animals using differentiated stem cells.

23. Describe the process of cloning via somatic cell nuclear transfer.

A3.5.4 Production of cloned embryos produced by somatic cell nuclear transfer.

24. Outline the production of Dolly the sheep using somatic cell nuclear transfer.

Dolly was the mammal to be cloned from an adult somatic cell using the process of nuclear transfer in 1996 (U3.5.8).