From: stevens@eatdust (John Stevens)
Newsgroups: alt.birthright,alt.abortion.inequity,talk.abortion
Subject: Re: Shameless attack on pro-choicers in general!
Date: 20 Aug 92 22:12:24 GMT
Distribution: usa
Organization: Are you kidding?  Of COURSE not!

In article <1992Aug15.231351.14657@csus.edu> chaneysa@nextnet.csus.edu (Stephen A Chaney) writes:
>In article <1992Aug14.022124.3457@ucsu.Colorado.EDU> knapp@spot.Colorado.EDU (David Knapp) writes:
>>In article <1992Aug10.161448.6148@csus.edu> chaneysa@nextnet.csus.edu (Stephen A Chaney) writes:
>>> Some direct questions are:
>>> 
>>> Do multiple births come from multiple eggs or from whacky things happening
>>> at early cell division stages.
>>
>>Identical twins derive from a single egg.  If the daughter cells
>>produced by mitosis of a zygote separate, you get identical twins.
>>Fraternal twins derive from two eggs, fertilized by separate sperm.
>>
>>> Is the same DNA in all cells?
>>
>>To a first approximation, YES.  There are exceptions.  For example,
>>eggs and sperm are haploid and have only half the genetic information
>>found in somatic (body) cells.  Mammalian red blood cells lack
>>nuclei at maturity and hence have NO nuclear DNA.  Those white blood
>>cells that give rise to the immune system splice out part of their
>>DNA as part of their differentiation to become specific for a
>>given antibody or T-cell receptor.
>
>Is he trying to tell us that stomach cells might accidentally mutate
>into zygotes? 

Possible, but highly unlikely.  And it wouldn't be 'mutation', exactly,
more an 'accidental' reactivation of the genes.

>
>Send this message to your professor: 
>
>1) Is the zygote the same as a skin cell or a stomach cell? 
>2) Seeing as the zygote is a differentiating cell with the full human
>DNA, does any other cell in the body have that DNA code and can it
>differentiate? 

All other cells (with the exceptions that the good proffessor mentions)
have the 'full human DNA'.  Different types of cells, have different
parts of the DNA active.

>3) What prevents a zygote from becoming a stomach cell or a skin cell?

A better question is: what keeps a stomach cell from growing into a
complete human being?  Answer: at the very least, a stomach cell has
parts of it's DNA inactivated (through the process of differentiation)
and the theory is that those parts of your DNA that control the process
of growing a complete human being from a single cell have been deactivated.

Conceivably, if you could reactivate those parts of the DNA, in a cell
with the right enviroment, in the right order, you could clone a man
from one of his intestinal cells.

>4) Why is it that stomach cells cannot produce skin cells, but that a
>zygote contains and grows out stomach, skin, brain and all other fetal
>and human (in general) body cells? 

Answered above.

>>"Brain activity" is not a single, simple thing.  Some parts of the
>>brain, such as the cerebellum and thalamus (for example) don't
>>specialize until the middle of the second month.  At about this
>>time, some reflexes are operative, and the brain may be regulating
>>some of the organs.  For this to happen, myelination has to have
>>taken place.
>
>Uh-oh. That means that by this standard (brain activity), abortion
>would be illegal somewhere in the 2nd month. Right before 90% of all
>abortions are actually done by D&C and suction curettage... 

Yeah.  This is one of the reasons the pro-choicers do NOT want brain
activity used as part of the definition of life.

>Or it means 
>1) You forged or misinterpreted the interview. 

No, all the information, allowing for the slight distortions of the
medium, and having been filtered through someone else, is correct.

>2) This professor comes from Berkeley. 

???? What does this matter?

>Major mistake. Ask your professor to answer this: 
>1) Can stomach cells produce skin or brain cells, yes or no?

If we had the technology (say, a COMPLETE understanding of the process
of DNA activation/expression) a stomach cell (or more likely, an
intestinal cell) could be modified to grow into a skin or brain cell.

>2) If the zygote can and does produce all these different cells, in
>addition to having his/her own determined gender at fertilization, what
>makes this happen? 

Already answered (though not in great detail).  Perhaps someone who
has recently taken a developmental biology course can go into the
details of the differences (other than genetic activation/expression)
in a fertilized egg, vs., say, a stomach cell.

>3) Does the mother continue to contribute to the z/e/f's DNA? Meaning,
>does she add arms, legs, a head and other things that the z/e/f cannot
>produce him/herself? Yes or no?

No.  The child's genetic endowment is complete after fertilization.

>4) What in the world is it in a z/e/f that runs his/her growth?

I (as you might expect) view the DNA as both a program, and a set
of blueprints for a computer.  The DNA has the program that controls,
directs and regulates the z/e/f's development.

>Sounds like you are the one lacking any intellegence, Knapp. Either
>that or you're forging.  

His professor is quite correct.  Your interpretation of the information
may differ, but the information given has no errors that I or my
exceedingly nit-picky biologist friends (and wife) can detect.

John
stevens@uswest.com
Xref: sparky alt.birthright:419 alt.abortion.inequity:3213 talk.abortion:32913