Types of Inheritance Patterns

curly hair CC x SS straight hair CS wavy hair 18.3 Beyond Simple Inheritance Patterns cont’ • Codominance —occurs when alleles are equally expressed in a heterozygote.

Dimples can be present on both cheeks or one, and some people have them on their chin. Like all physical traits that you possess you have two genes for them. One inherited from your father and one from your mother. The way that a physical trait is expressed, and hence the way you look is a result of either a combination of dominant genes, a dominant and a recessive gene or two recessive genes.

The Human Ear. In the same way that tongue rolling, widow's peak hairline, and cleft chins are thought to be perfect examples of simple dominant and recessive patterns of inheritance, so too is ear lobe attachment.

• Ff—freckles ff—fair skin . 18.2 One- and Two-Trait Inheritance • One-trait inheritance—involves one characteristic, determines if an individual with the dominant phenotype is homozygous or heterozygous. • 2 symbols and 4 offspring. • Punnett square—grid for working monohybrid crosses.

Hand clasping as a character Most people have a strong preference for clasping their hands in one way, either with the left thumb on top (L) or the right thumb on top (R). To most people, it feels unnatural to clasp the hands in the opposite way, making it a very easy trait to observe.

Like many complex traits, handedness does not have a simple pattern of inheritance. Children of left-handed parents are more likely to be left-handed than are children of right-handed parents. However, because the overall chance of being left-handed is relatively low, most children of left-handed parents are right-handed. Identical twins are more likely than non-identical twins (or other siblings) to be either right-handed or left-handed, but many twins have opposite hand preferences.

Inheritance odds for Red-green color blindness: Overall odds of inheritance: Usually inherited by males from their mother who is a carrier; see inheritance of x-linked recessive diseases. Sibling of diseased child odds of inheriting disease: About 50% for a second child if one (male) child already has the x-linked recessive disease.

The inheritance patterns observed will depend on whether the allele is found on an autosomal chromosome or a sex chromosome, and on whether the allele is dominant or recessive. Autosomal dominant. If the phenotype associated with a given version of a gene is observed when an individual has only one copy, the allele is said to be autosomal dominant.