1. Traits

2. Big Idea
DNA is the instructions for making proteins, proteins produce traits, traits make you YOU.

3. What is a trait?
A characteristic or feature of an organism

4. What types of traits are there?
Physical traits—height, eye color, hair texture
Behavioral traits—intelligence, nurturing behavior, facial expressions
Predisposition to medical conditions—high blood pressure, heart disease, cancer

5. How do we get these traits?
Traits can be produced by environmental factors: how you were raised, the food you eat, etc.
But many traits you are born with—and they are produced by proteins at work in your cells. Your proteins make you you!

6. How we get traits
Some traits are the work of a single protein—but most are the work of many proteins.
These proteins are created based on instructions in our genes.

7. Genotype and phenotype
The observable aspect of the trait is called the phenotype.
Example: Trait is eye color
Phenotype is brown (or blue, hazel, green, etc.)—the actual color that you see.
Genotype is the actual genes you have that produce your phenotype.

8. Dominant and recessive alleles
Different forms of the same genes are called alleles.
Every person has two alleles for each gene (although there could be many more alleles in the population as a whole).
If it only takes one allele to produce a certain trait, that allele is called dominant: it masks the effect of the other allele.
If a trait is produced only when two of the same allele are present, that is called recessive.

9. Genotype possibilities for single gene traits
Trait: ability to roll tongue
Tongue rolling is dominant—it takes only one allele (call it R) to be a tongue roller. So the other allele could be another R—or it could be the recessive allele (call it r). So our two possibilities are RR or Rr.
For a person who cannot roll their tongue, there is only one possibility because this is a recessive trait: rr

10. Example: Earlobes—attached (left) or unattached
EE or Ee ee

11. Widow’s peak (left) or straight hairline
WW or Ww ww

12. Big toe longest or second toe
SS or Ss ss

13. Hitchhiker’s thumb or straight thumb
TT or Tt tt