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Human Genetics:
Dominant & Recessive Traits
Copyright © 2004 Stevens Institute of Technology, CIESE, All Rights Reserved.
Human Genetics:
Dominant & Recessive Traits
• The physical characteristics below are
common genetic traits inherited from one
generation to the next:
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Free vs. Attached Earlobes
Straight vs. Curved Thumbs
Bent vs. Straight Pinky
With vs. Without White Forelock
• Review the following slides that contain:
 Definition and images of each genetic trait
 Identification of the Dominant / Recessive trait
Copyright © 2005 Stevens Institute of Technology, CIESE, All Rights Reserved.
Free vs. Attached Earlobes
• Free earlobes (dominant
trait) hang below the point of
attachment to the head.
• Attached ear lobes
(recessive trait) are attached
directly to the side of the
head.
Copyright © 2005 Stevens Institute of Technology, CIESE, All Rights Reserved.
Straight vs. Curved Thumbs
• Straight thumbs (dominant
trait) can be seen as nearly a
straight line and may contain
a slight arch when viewed
from the side as in the
illustrations.
• Curved thumbs (recessive
trait) can be seen as part of
a circle.
Copyright © 2005 Stevens Institute of Technology, CIESE, All Rights Reserved.
Bent vs. Straight Pinky
Bent pinky (dominant trait)
vs. Straight pinky
(recessive trait):
1. Hold your hands together as if
you are covering your face.
2. If the tips of the pinkies (or
baby fingers) point away from
one another, the pinkies are
bent (dominant trait).
Copyright © 2005 Stevens Institute of Technology, CIESE, All Rights Reserved.
With vs. Without White
Forelock
• A White Forelock (dominant
trait) is a patch of white hair,
usually located at the hairline
just above the forehead. The
photo to the left clearly shows
an exaggerated white
forelock.
• No White Forelock is the
recessive trait.
Copyright © 2005 Stevens Institute of Technology, CIESE, All Rights Reserved.