Genetic Inheritance Patterns

Dominant and Recessive Genotypes & Phenotypes

Jan 29, 2008
Tami Port

Gregor Mendel, Father of Genetics - Public Domain, Copyright expired, Wiki

Collection of articles exploring simple inheritance of human genetic traits, including earlobe attachment, dimples, myopia, eye color, cleft chin, and hand clasping.

Heredity is the transfer of characteristics from parent to offspring through genes. A gene, the “unit of heredity,” is made of deoxyribonucleic acid (DNA). There are many genes on each molecule of DNA.

Genotypes & Phenotypes

The genotype is an organism’s genetic makeup. For example, all of your genes are what comprise your genotype. The expression of those genes is called your phenotype, your traits that result when the instructions in your genes are carried out.

Alleles

Alleles are variations of a gene. We get one set of alleles (genes) from one parent and the other set of alleles from the other parent.

Some of the traits that we have are based on simple inheritance where one version of a gene (dominant allele) masks the expression of the other version of that gene (recessive allele).

In writing, we represented dominant and recessive alleles with letters that distinguish the different types of alleles. A capital letter is used to represent the dominant allele and a lower-case letter is used to represent the recessive allele (example: dominant allele = P; recessive allele = p)

Homozygous and Heterozygous

When an organism has a pair of identical alleles for a character, they are said to be homozygous for that characteristic (PP, pp); the other option, two different alleles for a gene (Pp). This would represent the heterozygous condition for a characteristic.

Quick Links to Articles on Specific Inheritance Patterns

Complete Genetic Dominance: Examples of Simple Inheritance: Melanin (Eye Color) & Myopia

Learn about genetic traits by examining some of your own! This article explores the genetic of iris pigment and nearsightedness.

Simple Genetic Inheritance: Complete Dominance: Facial Dimples, Chin Cleft & Free Earlobes

Understand heredity first hand by examining actual examples of dominant phenotypes. The dominant trait is not always the most common!

Dominant Human Genetic Traits: Complete Dominance of Mid-digital Hair, Hand Clasping & Bent Finger

It's much easier to understand genetics and heredity if you examine actual examples of dominant and recessive phenotypes that you possess.

Genotype, Phenotype & Heredity: The Inheritance of Homozygous and Heterozygous Characteristics

What is the relationship between genes, chromosomes and DNA? Genotypes, phenotypes and alleles? Read on to learn how inheritance works.

More Genetics Resources

See the science education website Science Prof Online for more information of genetic inheritance patterns or look to other Genetics & Evolution Suite 101 articles.