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![](/olcweb/styles/shared/spacer.gif) | ![](/sites/dl/free/0072324813/title/mader_human7e.jpg) Human Biology, 7/e Dr. Sylvia S. Mader
Genes and Medical Genetics
Chapter Outline
20.1 Genotype and PhenotypeThe physical characteristics of an individual are controlled by inherited genes. 404Dominant genetic traits appear if a single dominant allele is inherited; recessive genetic traits require the inheritance of two recessive alleles. 404 |
![](/olcweb/styles/shared/spacer.gif) | ![](/olcweb/styles/shared/spacer.gif) | ![](/olcweb/styles/shared/spacer.gif) | 20.2 Dominant/Recessive TraitsIt is possible to determine the chances of an offspring inheriting a particular parental gene, and therefore a particular condition. 405Pedigree charts are used to determine the pattern of inheritance for a condition that runs in the family. 409 |
![](/olcweb/styles/shared/spacer.gif) | ![](/olcweb/styles/shared/spacer.gif) | ![](/olcweb/styles/shared/spacer.gif) | 20.3 Beyond Simple Inheritance PatternsCertain traits, such as skin color, behavior, and various syndromes, are polygenic. 411Blood type is controlled by multiple alleles. 412Some traits, like sickle-cell disease, are incompletely dominant. 413 |
![](/olcweb/styles/shared/spacer.gif) | ![](/olcweb/styles/shared/spacer.gif) | ![](/olcweb/styles/shared/spacer.gif) | 20.4 Sex-Linked TraitsSex-linked traits are usually carried on the X chromosome. Males, with only one X, are more likely to express X-linked traits. 414Some traits are sex-influenced rather than sex-linked. 418 |
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