The Four Types of Inheritance Patterns in Pedigrees

Autosomal, X-linked, Dominant, and Recessive

There are four types of Mendelian inheritance patterns: Autosomal, X-linked, Dominant, and Recessive.

Autosomal- This is a non-sex determining chromosome meaning that males and females have an equal probability of passing on the trait to offspring. For example, eye color can be autosomal but this can be further identified as being dominant or recessive.

X-linked- All X-linked traits only occur in males because they only have one copy of the X chromosome. This is known as being sex linked. Women do not show X-linked traits or diseases. For example, hemophilia is an X-linked disease and can only be passed via the X chromosome.

Dominant- A condition or trait only occurs in individuals who have two copies of the allele in question. This can be seen in plants were shapes are often dominant such as having rounded features. If two copies of the allele for rounded features are present this would be a dominant feature in the plant.

Recessive- A condition or trait that only occurs in individuals who have two copies of the allele for a trait where a dominant allele is not present. For example, in order for a plant to be short it must contain to recessive alleles for this characteristic.

References

Simon, E. J., Reece, J. B., & Dickey, J. L. (2010). Essential biology with physiology. (3rd ed.). San Francisco, CA: Pearson/Benjamin Cummings.

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