Download Mendelian Traits in YOU!

Mendelian Traits in YOU!
• The presence of mid-digital hair is a dominant
condition; therefore those lacking it are
homozygous recessive.
Freckles are controlled primarily by
the MC1R gene. Freckles show a
dominant inheritance pattern:
parents who have freckles tend to
have children with freckles.
Variations, also called alleles, of
MC1R control freckle number.
Freckles are small, concentrated spots of a skin
pigment called melanin. Most fair-skinned, redhaired people have them.
Other genes and the environment
influence freckle size, color, and
pattern. For example, sun exposure
can temporarily cause more
freckles to appear.
Some people can curl up the sides of their tongue to
form a tube shape. In 1940, Alfred Sturtevant
observed that about 70% of people of European
ancestry could roll their tongues and the remaining
30% could not.
Many sources state that tongue
rolling is controlled by a single
gene. However, as Sturtevant
observed, people can learn to roll
their tongue as they get older,
suggesting that environmental
factors—not
just
genes—
influence the trait. Consistent
with this view, just 70% of
identical twins share the trait (if
tongue rolling were influenced
only by genes, then 100% of
identical traits would share the
trait).
• A distinct downward peak of the frontal hairline
• Having a widow’s peak is a dominant trait.
• Homozygous recessive individuals possess a straight
hairline.
• Is your earlobe attached or unattached?
• Free or unattached earlobe is dominant.
• The homozygous recessive condition is expressed as a
direct attachment of the earlobe to the head.
Dimples are small, natural indentations on the
cheeks. They can appear on one or both sides,
and they often change with age. Some people
are born with dimples that disappear when
they’re adults; others develop dimples later in
childhood.
Dimples are highly heritable, meaning that people who
have dimples tend to have children with dimples—but
not always. Because their inheritance isn't completely
predictable, dimples are considered an “irregular”
dominant trait. Having dimples is probably controlled
mainly by one gene but also influenced by other genes
Round hair follicles make straight hair, flattened or cshaped hair follicles make curly hair, and oval hair follicles
make wavy hair. Hair texture is a continuous trait,
meaning that hair can be straight or curly or anywhere in
between.
Curly hair is influenced by genes much more than by the
environment. While curly hair runs in families—people
with curly hair tend to have children with curly hair—its
inheritance patterns are often unpredictable.
Multiple genes control hair texture, and different variations in these genes are
found in different populations. For instance, curly hair is common in African
populations, rare in Asian populations, and in-between in Europeans. Straight hair
in Asians is mostly caused by variations in two genes—different genes from the
ones that influence hair texture in Europeans. And different genetic variations make
hair curly in African and European populations.
• Hyperextensibility of the thumb is recessive.
• Those who cannot bend at least one thumb backward
about 45 degrees are probably carrying the dominant
gene.
Sorry… But no
hitchhikers
thumb…
• Can you taste the bitterness of the
PTC paper?
• People who can taste the
bitterness are either homozygous
dominant (TT) or heterozygous
dominant (Tt).
• People who cannot taste the
bitterness are homozygous
recessive.