There are different kinds of DNA. The two basic kinds are Nucleic DNA and Mitochondrial
DNA (mtDNA).
Mitochondrial DNA (mtDNA) is found in the "body" or cytoplasm of the cell. It
is doughnut shaped and is passed from mother to child. Males have Mitochondrial DNA and
can do the mtDNA for genetic genealogy for their material line but males do not pass
Mitochondrial DNA (mtDNA) to their children. The little bit of Mitochondrial DNA that is
part of a sperm cell that fertilizes an egg cell is "digested" by the egg cell
at the time of fertilization.
Nucleic DNA is found in the cell nucleus. This is the double helix shape that people
typically think of when they think of DNA. In humans, the Nucleic DNA is made up of 23
pairs of chromosomes. One of those 23 pairs is the sex chromosome. The sex chromosome is
either XY (for male) or XX (for female). The 22 pairs of chromosomes that are not the sex
chromosome are called autosome DNA.
Because there are different kinds of DNA (and different questions that are being asked),
there are different kinds of DNA tests. Typically, a DNA test to determine if a
particular person is a child of a specific person looks at sections from all of the
23-pairs of chromosomes.
The Y-DNA test that is used in genetic genealogy for the paternal line is looking at only
the Y half of one of the 23-pairs of chromosomes.
The Family Finder DNA test offered by Family Tree DNA looks at sections of the autosome
chromosomes but this test should not be used as a paternity test. That is not what it was
designed for. Use the tools only for the jobs they were designed to do. For genetic
genealogy questions, use genetic genealogy tests. For paternity questions, use a
paternity test.
Y-DNA and mtDNA are commonly used for genetic genealogy specifically because they are
typically passed from generation to generation without change. You know where a
person's Y-DNA and mtDNA came from. The Y-DNA came from the father. The mtDNA came
from the mother. All of the other DNA gets randomly mixed up from generation to
generation so you don't know which parent it came from unless you test a lot of
cousins and even then it is a lot of work to track out who got what from where. Autosomal
DNA testing can get complicated but it can answer questions not answered by the simple
Y-DNA and mtDNA tests if you are willing to put in the extra work to interpret the
results.
Assuming your step-daughter used a reliable paternity testing company, I would assume the
test results are valid. It works like this: Chromosomes come in pairs. One part of each
pair comes from the mother. The other part of each pair comes from the father.
For example, for one particular chromosome pair, a man might have 11-22 and a woman might
have 33-44.
If this man and woman had a child together, that child would inherit either 11 or 22 from
the father and either a 33 or 44 from the mother. So the child could be:
11-33
11-44
22-33
22-44
If the child turned out to have 55-33 then you know the man who was tested (who had only
11-22) could not have been the father.
Date: Sat, 17 Dec 2011 09:53:47 -0700
From: beth.a.mck(a)gmail.com
To: carter(a)rootsweb.com
Subject: Re: [CARTER] CARTER Digest, Vol 6, Issue 71
#2 - Only males have Y-DNA. Females do not have Y-DNA.
My husband's daughter by a previous marriage was questioning her parentage.
Her mother has passed on, so she could not directly ask her. She did a DNA
test with another man she thought might be her father and it turned out
positive...So I am confused...Does this mean her test results might be
mistaken?
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