This document discusses human traits and how genes influence them. It explains that traits are physical characteristics that make people differ from one another, such as hair color, eye color, height, etc. Genes determine traits by providing instructions to the body. Genes are passed down from parents and can determine traits like hair color, texture, whether one can roll their tongue, taste bitterness, and more. The document uses examples like eye color, tongue rolling, and taste sensitivity to illustrate Mendelian genetics and how traits are inherited.

1. Traits
Cam-Tu Diep

2. Traits
• Look at the people around you. No other person looks or acts
just like you. The ways in which people differ are called traits.
Our
differences
are called
traits.

3. People have many different traits
• Hair color
• Skin color
• Eye color
• Height
• Freckles
• Earlobes
• Nose shape Red hair is a trait.
So are blue eyes.
• Traits help us tell people apart. Traits are
differences between people.

4. We also share many of the same traits
• We walk with twos legs
• We sing and speak
• Our hands look like other people hands.
• People are more like one another than like
animals. All people
have the
same basic
parts.

5. So what make these different traits?
• Genes tell your body how to make different
traits. Genes are like instruction for the body.
• You got your genes from your birth parents.
Genes tell your body how to work and grow.
• Genes come in pairs. One copy came from each
parent. One from your mom. The other came
from your dad. The copies are called alleles.

6. Gregor Mendel
• The father of modern genetic
• Mendel studied dichotomous
traits & how they are passed
on to offspring
• Mendel demonstrated that the
inheritance of certain traits in
pea plants follows particular
patterns, now referred to as
the laws of Mendelian
inheritance.

7. Mendelian Genetics
• 2 possible "alleles" for each trait
• The combination one has (1 from
mom, 1 from dad) is called your
"genotype"
• 2 matching alleles = "homozygous"
• 2 different alleles = "heterozygous"

8. • In heterozygous individuals, the allele
that is "expressed" (seen in individual’s
appearance) is the "dominant" allele.
• The allele that is not expressed is the
"recessive" allele
• The traits that are expressed make up
your "phenotype"
• There are more than 2 alleles for some
traits
• Most traits, in fact, are affected by more
than 1 gene

9. Tongue Rolling
Genes play a part in tongue rolling. Many people roll
their tongues easily. Others can roll their tongues a little.
Some people cannot roll their tongues. Sometimes
people can learn to roll their tongues with practice.
Rolling up edges (dominant trait) vs not rolling (recessive)

10. Traits
• Sometime you need two alleles to get a trait.
Other times, you need just one allele.
You needed two
alleles to have
red hair.

11. It takes just one
freckle allele to
Freckles give a person
freckles.
Freckles are traits. Freckles are spot on the skin.
Pigment makes freckles. Pigment gives skin its color.
Do you
It’s spread out in those without freckles. have
It’s clumped together in those with freckles. freckles?
Pigment is a substance that gives color to something.

12. Hair Color
Your gene tell the body to make certain pigments.
Pigments color hair.

13. Some member of
this family have
Hair traits straight hair other
have curly hair.
For many traits, one of a pair of genes takes control. But that’s
not true for hair texture.

14. Ear Traits
Look at the bottoms of these ears.
Can you tell how they are different?

15. Nose Traits
Noses come in many shapes.
Gene help decide the shape of
your nose. Some noses are
big. Some are small. Some
curve out. Some are straight.
Some even have turned-
up end.
What is the shape of your
nose? Is it curved or
straight?

16. Which thumb is on top?

17. Left Brain, Right Brain

18. Dimples
Dimples are small dents in a person’s skin. These kids
have dimples on her cheeks.
Dimples: Dimples (dominant trait) vs. No dimples (recessive trait)

19. Cleft chins
Cleft chins has a crease down the middle.
Cleft chin is dominant over no cleft.

20. Hitchhiker’s thumb
Make a fist with one hand.
Then hold put your
thumb. Is it bent? Or is
it straight? A thumb
that bends like this one is
a hitchhiker’s thumb.

21. Double-Jointed

22. Double-Jointed
This girl have
double-jointed
elbow

23. Hands and Pinkies
Do you have hair on the middle This man has some hair on the
parts of your fingers? middle part of his fingers. Some
people don’t have any hair.

24. Some traits are easy to see other traits
are hidden
Can you smell this? People like
some foods because of their
smell.

25. Not everyone smells the same smells.
Your genes play a roll in
what you can smell. Your
genes let you smell certain
scents. Hundreds of genes
control our sense of smell.
People have different alleles
of these genes. So everyone
smells things differently.

26. Asparagus
Most people smell a
funny odor after they
eat asparagus. And
the smell is in a
funny place. It’s in
their pee! But some
people smell nothing.
Scientists found that there are two different traits. The first trait is
whether you make the odor. The second trait is whether you can smell it.

27. Some traits are easy to see other
traits are hidden
Do you like
broccoli?
Broccoli contain a chemical called Phenylthio carbamide (PTC)

28. This boy got an allele from his mom for tasting
PTC. His dad passed along an allele that doesn’t
react to PTC. The PTC tasting allele takes
control. The boy taste PTC.

29. Other interesting facts about PTC
• -Only about half of Aboriginal peoples from
Australia and New Guinea are tasters. Nearly
100% of indigenous Americans (i.e. Native
Americans and Inuits) are tasters.
• -People who can taste PTC are more likely to be
non-smokers and to not be in the habit of drinking
coffee or tea. People who are super-tasters are
more likely to find green vegetables bitter.
• Women, Asians, and African-Americans are all
more likely to be super- tasters.

30. Your genes are part of
what makes you
What special traits
do you have?

31. Books
• Unusual Traits: Tongue rolling, Special Taste
Sensors, and more/ Buffy Silverman
• Body Parts: Double-Jointedness, Hitchhiker’s
Thumb, and More/ Buffy Silverman
• Facial Features: Freckles, Earlobes, Noses, and
More/ Jennifer Boothroyd
• Hair Traits: Color, Texture, and More/ Buffy
Silverman

33. Hair Color