Build a Family Tree (Men Only)
by Marti Louw
The Y chromosome is the keeper of family history on the male side. Written
in the letters of DNA, it carries a record of a man's paternal ancestors. Here
is your chance to try your hand at being a geneticist and solve a genealogical
puzzle using your power of reasoning and understanding of DNA.
When you start the game, you'll find an incomplete family tree of male relatives. We offer
simulated DNA sequences
from the Y chromosomes of 10 fictitious individuals. These men have a common ancestor and
the same last name, but only four of the individuals have been positively
identified and placed on the tree. Your job is to complete the rest of the male
family tree using DNA information from the Y chromosome.
The Y chromosome is passed from father to son as a nearly exact copy of itself.
It is not an identical copy, because during the DNA copying process, small
mutations can occur in the genetic code. It is these differences in DNA
sequences that allow geneticists to distinguish one individual from another.
The more closely related the family tie of two individuals, the more similar
their DNA sequences will be, since these mutations accumulate over the
generations. A father and son should have the most similar DNA sequences of
All the DNA sequences are made up of combinations of the letters A, C, G, and
T. These four letters represent the nucleic acids adenine, cytosine, guanine,
and thymine, which make up the DNA genetic code.
To figure out relatedness, you'll need to compare the order of letters between
the DNA sequences to find the differences, then use your powers of deduction to
figure out which individuals are most alike.
Marti Louw is an associate producer at NOVA.
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