Wednesday, May 30, 2007

The Genographic Project -II (Male carries the Ancestry)

We are still living is a male dominated society, where the Surname of male is still used as Family name.
Specially in India, we have some common believes that women are responsible for giving birth male child and only the male child can carry the ancestry.
The first one is definitely a misconception. We knew from the school that the sex of the child is determined by the father. Here is a small revision.
Male contains X and Y Chromosomes; Female contains X and X. So for a son the Y chromosome has to come from the Father.
But it is true that the family characteristics propagate through males. So “male child can carry the ancestry” is not a misconception. See the flowing explanations.
I have found the following 4 slides in http://www.dnaancestryproject.com/ ; where it tells

“A male inherits his Y-Chromosome directly from his father. The Y-Chromosome
that a male receives from his father is very special because it holds a lot of
valuable information about his ancestry. This is because the Y-Chromosome is
passed down along the male line, relatively unchanged from generation to
generation. A forefather will pass his Y-Chromosome down to all of his sons, and
they will then pass it down to all of their sons, and so on throughout the
generations along the male line. Thus, males who are descendents of the same
line will have the same or nearly identical Y-Chromosomes.”

"When a Y-Chromosome genealogy test is performed, the laboratory examines
specific regions (markers) along the Y-Chromosome called "hypervariable"
regions. Hypervariable regions are areas within the Y-Chromosome that may differ
greatly between different family lines. The type of hypervariable region which
is studied in Y-Chromosome testing is called STR markers (stands for "Short
Tandem Repeat" markers). STR markers are regions of the Y-Chromosome where small chunks of the DNA are repeated over and over again. The number of times that these small chunks of DNA repeat themselves in the Y-Chromosome is variable amongst different family lines."

So, we can conclude that the unique ancestral traits are carried only by the male members because, all males with the same ancestors will have the same or similar Y DNA markers. For the female it gets overlapped with many different genes from mother sides.

After going through these slides, the basic question that came to my mind is if human is originated from single person, then the Y pattern (ATGC base patterns) will be same for all male in this world, which is not.

There are 2 possibilities. The first one if the initial set of Homo sapiens originated in different parts, who had different Y chromosomes. But still this one is not that convincing because as a consequence large section of human has to contain same Y patterns, which is not the reality.

Second possibility that came in my mind is Mutation (the abrupt change of Gene orientation of a species due to some external factors). This is the case probably, for details I have to dig more into the subject and will keep you updated.