| From: Peter Eagles | 16/02/2000
10:50:00 |
| Subject: DNA |
post id:
38925 |
| If twins are deemed "identical in
all respects" does that mean that their DNA is also "the same"? Also, if a human is cloned from the cell of another human, would the DNA be absolutely identical - even down to the finger prints? | |
| From: David Brennan | 16/02/2000
10:54:00 |
| Subject: re: DNA |
post id:
38927 |
| Identical twins have the same
DNA, yes, since they are from the same zygote. As for clones with the same fingerprints, I don't know, I thought fingerprints where affected by environment as well as genetics. David | |
| From: bec | 16/02/2000
11:11:00 |
| Subject: re: DNA |
post id:
38942 |
| Yes, David's right about
identical twins having the same DNA, but I don't think that fingerprints
are affected by the environment. A newborn baby has fingerprints before
it's had the opportunity to be exposed to the environment. I'm not sure
whether or not twins have the same fingerprints though. You'll notice that
even identical twins have slight differences about them. Although they may
have the same genes, each gene has a number of alleles (sort of like
choices or variants)which determine how that gene is expressed. eg. One
twin may have brown eyes and the other twin hazel.
| |
| From: David Brennan | 16/02/2000
11:18:00 |
| Subject: re: DNA |
post id:
38945 |
| OK, so these "choices" make the
differences in the appearence of genetically identical people. As for
babies in the womb not being affected by the environment, the womb is an
environment. Every place is an environment. The word have been hijacked a
little be the conservation lobby. What I mean was that small condition changes to each child during the pregnancy could lead to small changes in physical appearence later on, such as fingerprints and retina patterns(which after all is just the location of blood vessels). Very similar, but I can't imagine they would be identical. David | |
| From: bec | 16/02/2000
13:21:00 |
| Subject: re: DNA |
post id:
39010 |
| I don't think patterns like that
are identical. The alleles in each cell are switched on or off at random.
The chances of two individuals having exactly the same alleles switched on
in exactly the same cells would be 1 in god-knows-how-many million,
virtually nil. | |
| From: henry | 16/02/2000
14:39:00 |
| Subject: re: DNA |
post id:
39042 |
| if one twin commited a murder and
left DNA evidence at the scene of the crime (eg blood), is there any way
to tell which twin was guilty? henry< | |
| From: lentil | 16/02/2000
14:46:00 |
| Subject: re: DNA |
post id:
39046 |
| The DNA is identical, therefore
it would be impossible to tell which twin was the evil
one | |
| From: bart | 16/02/2000
14:49:00 |
| Subject: re: DNA |
post id:
39047 |
| If one of the twins is pregnant
she will have orange plasma. | |
| From: lentil | 16/02/2000
14:58:00 |
| Subject: re: DNA |
post id:
39053 |
| From the
internet Identical twins have fingerprints that can be readily distinguished on close examination. However, the prints do have striking similarities. In fact, before the arrival of modern genetic testing, similarity of fingerprints was often used to determine whether twins were identical or fraternal. (Identical twins, you'll recall, are genetic duplicates who develop from a single egg. Fraternal twins develop from separate eggs and are no more closely related than ordinary siblings, except that they spend nine months sharing an extremely small bedroom.) Twin fingerprints are much beloved by scientists, who see them as a classic arena for the old nature-versus-nurture debate: What made you what you are today, your genes or your environment? Twin fingerprints clearly show that it's a little of both. If you compare palm prints and fingerprints of the Dionne quintuplets (born in 1934, they were the first quints of which all five survived), you find that the broad-brush pattern of lines, whorls, loops, etc., as well as what researchers call "ridge count," were quite similar for the whole crew. Nonetheless each kid had unique prints due to differences in detail. "There is as yet no evidence that the arrangement of the minutiae (ending ridges, bifurcating ridges, etc.) is in any way genetically influenced," writes fingerprint expert James Cowger. Presumably these minor but crucial differences arise from random local events during fetal development, the same kind of thing that makes each snowflake unique. http://www.straightdope.com/classics/a980821.html | |
| From: Rapunzel | 17/02/2000
1:51:00 |
| Subject: re: DNA |
post id:
39274 |
Good stuff, Lentil! Even identical twins are not identical in all respects, even physically. Environmental differences cause physical differences. And there may even be some (albeit small) DNA differences due to mutations - particularly if they occur during early embryonic development. | |