The apple doesn't fall far from the tree, genetically speaking. While children generally aren't a carbon copy of their parents, they do share inherited physical characteristics, from eye color to the length of their toes and shapes of their earlobes. With some physical characteristics, a number of genes go into their creation, so your toddler or preschooler could have physical traits neither of you possess.
1. How Genetics Works
Every child born inherits half his genetic material from mom and half from dad. Each parent contributes 23 chromosomes, which carry genes that determine different traits.That doesn't mean your child will end up with half your characteristics and half your partners, though. Some characteristics are dominant, meaning that if your child inherits that gene, he'll have that characteristic. So if you have mostly dominant genetic traits and your partner has mostly recessive genes, your child could take more after you than him. But that's a simplification for most physical inherited traits. Most genes carry two or more alleles, or variations, inherited from each of your parents, so your child could inherit a trait neither of you possess.
2. Single Gene Traits
The more scientists learn, the less they actually know about genetic traits. The following traits have traditionally been considered as traits controlled by a single dominant gene, but more study might refute this. An attached or unattached earlobe, with the unattached earlobe being dominant, is one. The ability to roll your tongue is also considered a dominant trait. Colorblindness, curly hair, freckles, cleft chin, dimples, the way you clasp your hands, a tendency to develop allergies and handedness fall into the category of traits considered single gene dominant traits.
3. Recessive Genes
If you have a recessive physical trait, your child must inherit two copies -- one from each of you -- for the trait to appear. For example, if your child has blue eyes, he probably inherited one blue-eyed gene from each parent. This can happen, even if you both have brown eyes. Blue eyes are generally recessive, although eye color, like many traits, appears more complex the more scientists study it. So you might each carry a blue-eyed gene you could pass to your child. In blood types, type A is dominant over O, so if you have type O blood, you inherited this trait from two parents.
4. Codominant or Polygenic Characteristics
Some genes are neither totally dominant or recessive, meaning that the combination could result in a mixture of physical traits rather than one or the other. This happened if your child has type AB blood. He inherited a gene for type A from one parent and a gene for type B blood from the other, but since neither is dominant over the other, he has type AB blood. Height, weight and hair and skin color exemplify characteristics influenced by several genes, called polygenic traits.
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