Cloning: There’ll Never Be Another You

Depending upon your point of view, cloning organisms may sound like a
nightmare or a dream come true. Whatever your opinion, cloning is most definitely
not science fiction; decisions about experimental cloning are being
made right now, every day. This chapter covers cloning: what it is, how it’s
done, and what its impact is from a biological point of view. Cloning (like just
about everything else in science) isn’t as simple as the media makes it sound.
In this chapter, you get to know the problems inherent in clones along with
the arguments for and against cloning (not just of humans — of animals and
plants, too). Get ready for an interesting story. Remember, it ain’t fiction!

cloning

The other use of the word cloning means to make a copy of an entire organism
as a reproductive strategy. When referring to a whole creature as opposed to
DNA, a clone is an organism that’s created via asexual reproduction, meaning
offspring are produced without the parent having sex first. Cloning occurs naturally
all the time in bacteria, plants, insects, fish, and lizards. For example,
one type of asexual reproduction is parthenogenesis, which occurs when a
female makes eggs that develop into offspring without being fertilized by a
male (for some of you female readers, I’m sure this sounds very appealing). So
if reproduction by cloning is a natural, normal biological process, what’s the
big deal with cloning organisms using technology?

Attack of the Clones

A clone is simply an identical copy. The word is used as both a verb, as in “to
clone” (make one) and a noun, as in “a clone” (have one or be one).
Genetically, the word clone can have two meanings. When geneticists talk
about cloning, they’re most often talking about copying some part of the DNA
(usually a gene). Geneticists clone DNA in the lab every day — the technology
is simple, routine, and unremarkable.

Cloning before Dolly: Working with sex cells

Experimental cloning started in the 1950s. In 1952, researchers transplanted
the nucleus from a frog embryo into a frog egg. This and subsequent experiments
were designed not to clone frogs but to discover the basis of totipotents.

cells rearrange

After a few more divisions, the cells rearrange into a three-layered ball called
a gastrula. The innermost layer of the gastrula is endoderm (literally “inner
skin”), the middle is mesoderm (“middle skin”), and the outermost is ectoderm
(“outer skin”). Each layer is composed of a batch of cells, so from the
gastrula stage onward, what cells turn into depends on which layer they start
out in. In other words, the cells are no longer totipotent; they have specific
functions.

therapeutic cloning

The promise of therapeutic cloning is that someday doctors will be able to
harvest your cells, use your DNA to make totipotent cells, and then use those
cells to cure your life-threatening disease or restore your damaged spinal
cord to full working order. Creating totipotent cells from nullipotent cells to
treat injury or disease is difficult and triggers significant ethical debates (see
“Weighing Both Sides of the Cloning Debate” later in this chapter). Realizing
the potential of therapeutic cloning may be a very long way off. Meanwhile,
reproductive cloning — the process of creating offspring asexually — is
already causing quite a stir. For a taste of some of the excitement, see the
sidebar “Aclone in the universe?”.