Developmental Psychology

Achieve Test Prep: Developmental Psychology

components: a genotype and a phenotype. The genotype is the actual genetic makeup, including dominant and recessive genes. • Dominant Genes: traits/genes which are always expressed • Recessive Genes: genes which are not expressed Phenotype is the observable traits which can be seen, such as eye color, hair color, and height. Many genes in the genotype are not observable. Unexpressed genes are called carriers . Unexpressed genes can be passed on to offspring. Genes can also act together in gene-gene interaction or with their environment in gene-environment interaction . Gene-Gene Interaction : • Additive: shows contributions of multiple genes o Ex. A tall woman has a child with a short man and the child is of intermediate height • Dominant-Recessive: genes are non-additive and are a ‘one or the other’ situation o Ex. An individual may have a dominant gene for brown eyes but be a carrier for blue eyes. Brown eyes are shown due to being the dominant gene. • Incomplete Dominance: phenotype is not completely controlled by genotype o Ex. Red flowers and white flowers produce pink flowers with a variety of pink hues. • X-Linked Genes: genes on the X chromosome can be dominant or recessive and are more common in men o Ex. Male pattern baldness is carried on the X chromosome Gene-Environment Interactions: The environment has varying effect on genetics. Studying twins, especially identical twins, helps scientists to study information about how environment influences genetics. Monozygotic, or identical twins, occur when one fertilized zygote splits into two identical clusters of cells which fully develop. Identical twins have identical genes. Dizygotic , or fraternal twins, occur when two eggs are fertilized by two different sperm at the same time. Fraternal twins are no more genetically similar than a brother and sister born by different pregnancies. It is assumed, though not always correctly,

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