Name:______________________________

Internet Biology/Cells in the News/Stem Cells

http://www.pbs.org/wgbh/nova/sciencenow/3209/04.html

 

Log on to the above site and click on “Watch the Segment”.  After watching the segment, click onto “The Cloning Process”, and answer the following questions.  If there is a down arrow at the bottom of the left-hand corner, click until done.

 

1.         What kind of cell was used for this demonstration?

 

Unless otherwise noted, images show mouse cells.

 

2.         How do they hold the egg cell steady for the surgical extraction?

           

They use a suction pipette and a glass needle.

 

3.         What is the zona pellucida?

 

The zona pellucida is the tough shell that surrounds the egg.  It protects the egg as it travels down the fallopian tube.  It also regulated fertilization so that only a single sperm may enter the egg.

 

4.         Define an “enucleated” egg

           

An egg that still contains proteins and RNA molecules but no nucleus.

 

5.         How is an unfertilized egg activated?

 

An egg is activated by chemical or electrical treatment that stimulated cellular division.

 

6.         Name and define the three parts of the blastocyst.

 

1.  Trophoblast—This goes on and forms part of the placenta.

2.  Inner cell mass—This is the part of the blastocyst that goes on to form the embryo after implantation in the womb.  This mass contains the embryonic stem cells. 

3.  Inner cell cavity—The definition is in the name.

 

7.         Define the term “passaging”.

 

Passaging happens when embryonic stem cells multiply to the point where the culture can expand to more tissue culturing dishes.

 

8.         Define the term “feeder cells”.

 

Feeder cells are connective tissue cells which supply important nutrients and hormones to the growing embryonic stem cells.

 

 

Click on “An Alternative to Cloning” and answer the following questions.

 

1.         What is “parthenogenesis”?

 

Pathenogenesis means that an egg activated spontaneously on its own without fertilization.  They look like embryos at the early stages.  They form blastocysts with stem cells inside.

 

2.         Why hasn’t pathenogenesis received much attention from the research community?

Pathenogenesis was unfortunately lumped in with the rest of embryo research; thus, scientists cannot get federal funding to do work on unfertilized human eggs.

 

3.         How are these eggs different from fertilized eggs?

Although these unfertilized eggs might occasionally end up in the uterus, there is no potential for an activated human egg to develop into any kind of embryo.

 

4.         Would this possibly be a way to sidestep a lot ethical concerns?

These embryos have no potential to develop into fully formed individuals.  This could possibly sidestep ethical concerns.

 

5.         Would everybody be able to benefit from parthenogenetically activated eggs?

 

These eggs can only create tissue-matched stem cells from women who are still ovulating.  Post-menopausal women and men could not use this form of therapy.

 

6.         What in your opinion is the biggest stumbling block to this type of research?

 

Answers will vary.

 

                 

After completing this set of questions, take the interactive poll found in the section “Should We Allow Cloning for Stem Cell Research?”.

 

 Click here F to return to Cell in the News Activity.