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Phenotype

Phenotype

Genotype and the environment affect the phenotype of an individual
Experiences in our lives and daily activities influence our phenotypes; nutrition, exercise, intelligence, sun tanning…

Norm of reaction

Genotype is not associated with a define phenotype, instead it is associated with a range of phenotypic possibilities due to environmental influences

The phenotypic range is called the norm of reaction for a genotype
In the norm of reaction the environment influences phenotypic expression

Multifactorial characters

Are characters that have their phenotypes influenced by a combination of genetic and environmental factors

Phenotypes produced by most genes and alleles are strongly influenced by the physical environment. This can be shown in the genetic disease, phenylketonuria (PKU).

PKU

The amino acid Phenylalanine accumulates in the body, resulting to the poor development of the nervous system and profound (showing) mental retardation.

If a low-phenylalanine diet is taken, individuals will develop normally.

References:

1) Biology. Seventh Edition, Neil A. Campbell and Jane B. Reece. Pearson Eduction Inc., publishing as Benjamin Cummings, 1301 Sansome St., San Franscisco, CA

2) Biology. Peter H. Raven, George B. Johnson, Susan Singer, Jonathan Losos. McGraw-Hill Science/Engineering/Math; 7 edition (January 8, 2004)

3) DNA Science: A First Course, Second Edition. David A. Micklos. Cold Springs Harbor Laboratory Press; 2 edition (January 8, 2003)