How Traits Are Transmitted From Parents to Offspring

Every adult that produces offspring, whether he means to or not, transmits traits to that offspring. This is because of genes, which are the makeup of our bodies, and the natural process of transferring this makeup to our offspring. People do not transmit traits solely through genetics, though -- they also transmit traits through behavior and environment. These are learned traits, and they may or may not be passed on at all, depending on the way the child is raised.

Genes

• Genes are the essence of heredity. Every human has thousands of genes, which are made up of DNA and chromosomes -- the building blocks of life. The fundamental concepts of genes and heredity were originally explained by Gregor Mendel, an Austrian monk who studied the way garden peas develop traits like shape and color based on their parents. He determined that the genetics of a parent determine the genetics of the offspring, confirming the basic notion of heredity.

Chromosomes

• Every person is made up of 46 chromosomes, 23 of which come from the mother and 23 of which come from the father. The father's sperm carries 23, as does the mother's egg, and when they meet, they form a zygote: a single cell with 46 chromosomes that eventually becomes a child. Chromosomes are contributed at random, so each child's 46 chromosomes come from an overall pool of 92 -- this makes a wide variety of combinations possible, which is why siblings look and act differently from one another despite having the same parents.

Dominant and Recessive

• Genes are determined by alleles -- genetic combinations that determine characteristics like hair and eye color. For example, the gene that determines whether a person can bend his thumb a certain way is comprised of two alleles. If both alleles are the same -- for example, they both give him the ability to bend his thumb backwards -- it is called homozygous. If one allele gives him this ability and the other doesn't, however, one allele overpowers the other. In this case, the dominant allele disables him from bending his thumb backwards. Though he has both alleles in his genetic code, one overrules the other.

Learned Traits

• Parents transmit traits to their offspring in non-biological ways as well. The way a child is raised makes her develop "learned traits," which are passed down by example or by teaching. For example, a child is born left-handed as a result of genetics, but a child that greets others with a handshake does so because of how she is taught to behave. Learned traits, when instilled at a young age, are nearly as deeply-ingrained in a child as genetic traits -- the child instinctively models herself and her own behavior on her parents.