Revision Summary Test 2

1a.What is the purpose of the cell cycle checkpoints? What happens when a cell no longer responds to these checkpoints?

2a.Outline the steps in creating a DNA profile.

3a.Summarize how genes are used to produce proteins.

4a.Describe the function of DNA replication.

5a.Explain why the genetic code is universal.

6a.How is transcription different from translation with respect to 1) location, 2) template, and 3) end product?

7a.Compare the structure of DNA and RNA.

8a.Describe how mutations in proto-oncogenes and tumor suppressor genes cause most types of cancer.

1b.How does codominance differ from incomplete dominance?

2b.Explain the difference between therapeutic cloning and reproductive cloning.

3b.Briefly describe the events involved in meiosis I and meiosis II.

4b.What is the function of meiosis in eukaryotic cells?

5b.Compare a multipotent stems cell with a pluripotent stem cell, using at least one example for each.

6b.Explain the difference between dominant and recessive alleles. Use the concepts of genotype and phenotype in your answer.

7b.In meiosis, what two processes occur that create diverse combinations of genes in egg and sperm?

8b.What potential gametes can result from an individual heterozygous for two traits, AaBb?

Summary

What is the difference between reproductive cloning and therapeutic cloning?

• Reproductive Cloning – making genetic copies of entire organisms.
• Therapeutic Cloning – making genetic copies of tissues or organs to replace damaged body parts.

Discuss four reasons why therapeutic cloning would be better than standard organ donation.

1. No waiting for donor organs.
2. No organ rejection.
3. Replace damaged parts of organs.
4. Replace body parts that can’t be donated.

What are the three requirements necessary for a cell to be used in cloning?

1. Contains a complete genome.
2. Can undergo mitosis.
3. Daughter cells can differentiate into many roles.

Discuss the differences between terminally differentiated cells, multi-potent cells, and pluripotent cells. Which can be used in cloning? Which can’t be used in cloning, and why not?

• Terminally differentiated can’t be used in cloning since these cells can’t undergo mitosis.
• Multi-potent cells can’t be used in cloning since the daughter cells can’t differentiate into enough cell types.
• Pluripotent cells can be used in cloning.

Where are human pluripotent cells normally found?
Blastocyst in the early human embryo.

In an adult human body, how common are terminally differentiated cells, multi-potent cells, and pluripotent cells?

• Most cells are terminally differentiated.
• A few cells are multi-potent.
• None are pluripotent.

What are stem cells? Name two different kinds of stem cells, where they are located, and how they
differ.
Stem cells are any cells that can reproduce and whose daughter cells can take on a variety of different roles.

1. Adult stem cells are multi-potent, and are found in all adult tissues.
2. Embryonic stem cells are pluripotent, and are found in embryos during the first few days of development.

Discuss three different methods for obtaining pluripotent cells.

1. Remove embryonic stem cells from blastocysts.
2. Reprogram adult stem cells to become pluripotent.
3. Reprogram adult terminally differentiated cells to become pluripotent.

Explain both positive and negative aspects of obtaining pluripotent cells from blastocysts.
Positive –

1. Easy to obtain cells.
2. Blastocysts are plentiful (leftovers from fertility procedures)

Negative –

1. Must destroy embryos.
2. Cloned tissue or organs may be rejected by patient’s immune system.

How can multi-potent adult stem cells be reprogrammed into pluripotent cells?
Remove own adult stem cells. Inject them into the damaged organs. Cells become pluripotent and replace all different kinds of damaged cells.

Explain both positive and negative aspects of obtaining pluripotent cells from reprogrammed adult stem cells.
Positive –

1. Embryos are not destroyed.
2. No rejection.

Negative –

1. Adult stem cells are difficult to obtain.
2. Adult stem cells don’t always become pluripotent.
3. This method might repair damage but don’t replace entire organs.

Discuss three steps necessary for reprogramming terminally differentiated cells into pluripotent cells.
Step 1 – Get The Enzymes

Step 2 – Putting The Enzymes Into a Terminally-Differentiated Cell

Step 3 – Providing The Right Conditions –

Why can unfertilized eggs be used to reprogram cells into pluripotent cells?
Use nuclear transplantation to use the enzymes found in an unfertilized egg that turns genes back on.

Discuss the process of nuclear transplantation. What is it used for, and how do you do it?
can be used to reprogram terminally differentiated cells back into pluripotent cells. The haploid nucleus of an unfertilized egg is removed. The egg is then fused with a terminally differentiated cell. Enzymes within the egg turn all of the genes in the nucleus back on again.

What animal was the first to be cloned with nuclear transplantation, and in what year? Why was this an easier animal to work with than mammals or birds?
In 1958, with African clawed frogs, Xenopus laevis.

What was the first mammal to be cloned with nuclear transplantation, and in what year? Why were three animals used to create the clone?
To be cloned this way was a female sheep (a ewe), in 1996.

Since the original Dorset sheep was female, they could have used one of her own unfertilized eggs, and implanted the embryo in her own uterus. In other words, they could have used just one animal.

Assuming that you want to reproductively clone a female animal using nuclear transplantation, how many adult animals are absolutely necessary?

Why is reproductive cloning with nuclear transplantation easier than therapeutic cloning?
One.

Explain both positive and negative aspects of obtaining pluripotent cells by reprogramming terminally differentiated cells with nuclear transplantation.
Positive –

1. Terminally differentiated cells are easy to obtain.
2. No rejection.

Negative –

1. Complicated, difficult procedure.
2. The reprogrammed cells becomes an embryo which is destroyed in the process.
3. It can be used for reproductive cloning in humans.

What are induced pluripotent stem cells, and how are they created?
pluripotent cells produced by adding transcription factors to a terminally differentiated cell. The guy reverted terminally differentiated cells back into pluripotent cells by using a virus to inject the genes into the cells. In other words, he used genetic engineering to create pluripotent cells.

What are transcription factors?
Four enzymes that, together, can transform a terminally differentiated cell into a pluripotent cell.

Why might iPSCs be less controversial to use for therapeutic cloning than cells created with nuclear transplantation?
Embryos are neither created, nor destroyed, with this method.
In any event, research into this process is at a very early stage. Even though cloning other mammals is now routine, it’s more difficult with human cells. Cloned human embryos, made via nuclear transplantation using DNA from an adult cell, were only just created for the first time – in 2014. These cells were grown into insulin-making cells, which have the potential to treat or cure diabetes.

What is another name for therapeutic cloning?
Therapeutic cloning is also known as somatic cell nuclear transfer.

In February 2004, a team of South Korean scientists managed to generate more than thirty human blastocysts
by therapeutic cloning. How many human embryonic stem cell lines were produced by this technique?
These scientists produced a single human embryonic stem cell line from these embryos.

What is the current “bottleneck” in therapeutic cloning?
The current “bottleneck” is the low efficiency that occurs when stem cell lines are prepared from
cloned blastocysts.

What is the difference between reproductive cloning and therapeutic cloning?
Reproductive cloning involves cloning a person’s DNA, and transplanting the embryo into a
(surrogate) mother for the sole purpose of producing a new human being. Therapeutic cloning is the development
of human blastocysts for the sole purpose of producing stem cell lines for therapeutic use in humans.

In addition to embryonic stem cells, what other type of human tissue contains stem cells that show potential in
the treatment of human diseases?
Stem cells are also found in human umbilical cords.

What recommendation has been made on therapeutic cloning in a report by the U.S. President’s Council on
Bioethics in July 2002?
This council recommended that cloning for biomedical research be prohibited during a four-year moratorium.

In June 2007, a bill was presented to President George W. Bush that would allow the use of federal funding for
embryonic stem cell research. What was the outcome of this legislative action?
President Bush vetoed the stem cell research bill. He stated that this bill was would support the
deliberate destruction of human embryos. This was President Bush’s second veto of embryonic stem cell
research legislation since he took office in January 2001.