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Asked by: Dominick Ponzi
School:George F. Johnson Elementary School
Teacher:Miss Williams
Hobbies/Interests:training my puppy
Career Interest:Electrical engineer


Answered by: D. Andrew Merriwether
Title:Associate Professor, Binghamton University
Department:Anthropology and Biology
About Scientist:Research area:
Molecular Anthropology, Population Genetics, Molecular Evolution

Ph.D. school:
University of Pittsburgh (Ph.D. in Human Genetics from the Graduate School of Public Health)

Wife: Ann, daughters Kenny (12) and Helen (9)

Raising Alpacas, playing softball, watching baseball and football, movies.

Web page address:


Date: 11-15-2006

Question: Why don't offspring have all their parents inherited traits?

Answer: Good question. Each person has two copies of every chromosome (and all the genes that are on it); they inherit one from each parent, one copy via the sperm from the father and one copy via the egg from the mother. The two copies usually have subtle differences in their sequences (mutations) that cause the genes to produce different traits. Since the father and the mother also have two copies of each gene, and only one copy can end up in each sperm or egg, it is random which copy ends up in each sperm or egg cell. Since there are 23 pairs of chromosomes, there are 8,388,608 different possible combinations of chromosomes that can be created by each parent in each sperm or egg. That does not take into account something called recombination, which mixes up the DNA between the maternal and paternal copies of each chromosome during meiosis, creating an almost infinite number of possible combinations.

It is a wonder siblings look alike at all. On average, full-siblings share half of their mutations in common with each other and with each parent. Lastly some mutations are dominant over others and prevent the expression of other traits. There are many other even more complex ways genes can interact, but the few ways I have listed here make it easy to understand why you and your parents are not exactly the same.

Ask a Scientist appears Thursdays. Questions are answered by faculty at Binghamton University.  Teachers in the greater Binghamton area who wish to participate in the program are asked to write to Ask A Scientist, c/o Binghamton University, Office of Communications and Marketing, PO Box 6000, Binghamton, NY 13902-6000 or e-mail Check out the Ask a Scientist Web site at To submit a question, download the submission form(.pdf, 460kb).

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Last Updated: 6/22/10