Emma and Anna Are Identical Twins Who Were Adopted by Different

question 109

Multiple Choice

Emma and Anna are identical twins who were adopted by different families a few weeks after birth.Although genetically identical,they grew up with different physical and psychological characteristics.For example,though both inherited a tendency to grow large,Anna was slim and athletic due to the active lifestyle practiced in her adoptive family.This variability can be explained by how:

• A)each zygote is unique.
• B)longevity genes can make an individual less vulnerable to certain diseases.
• C)for each genotype,a range of phenotypes can be expressed.
• D)mutated genes can be a source of genetic variability.

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Definitions:

Optic Ataxia

Deficit in the visual control of reaching and other movements.

Visual-Form Agnosia

Inability to recognize objects or drawings of objects.

Receptive Field

The specific area within the visual field that a particular sensory neuron responds to.

Rods

Photoreceptor cells in the retina of the eye responsible for vision at low light levels, important for night vision.