1. Traits/Variations/Mendel
Unit 4 Part 2

2. How do we look the way we do?
Proteins control our traits
What is a trait?
a specific characteristic, for example, eye color or height that varies from one individual to another.
The differences among these traits are called variations?
the differences that an organism can inherit for a trait

3. Who discovered all this?
Gregor Mendel
Father of Genetics
First person to describe how traits are passed on from each generation.
Austrian monk in the early1800’s
Discovered the principles of genetics
Studied 7 characteristics of pea plants

4. Why peas? Mendel studied peas for several reasons
They have distinct male and female parts
There are 7 basic characteristics of pea plants
They can self-pollinate and cross-pollinate.

5. Terms to Know:
Cross
combining gametes from parents with different traits
Self-Pollinate
pollination that occurs from the joining of pollen and ovary of the same flower
Cross-Pollination
pollination that occurs from the joining of pollen and ovary of different flowers
Allele
different forms of the same gene, the genes you inherit from your parents.
Gene
located on chromosomes, they control how an organism develops
Fertilization
the uniting of male and female gametes

6. Green pea pods x green pea pods
Mendel’s experiment
Cross pollinated
Green pea pods x green pea pods
= All green pods
Self pollinated
Green pods x green pods
= ¾ green pods
¼ yellow pods
Mendel took two pea plants and crossed them.
What did he find?
He discovered different laws and rules that explain factors affecting heredity.

7. Mendel’s Laws/Rules Law of Dominance Law of Segregation
The trait that is observed in the offspring is the dominant trait (Use uppercase letters to describe)
The trait that disappears in the offspring is the recessive trait (use lowercase letters to describe)
The two alleles for a trait must separate when gametes are formed
A parent randomly passes only one allele for each trait to each offspring

8. More Terms to Know Dominant The trait that is observed or expressed
Use a capital letter (T)
Recessive
The trait that is covered up or not expressed
Use a lowercase letter (t)
Heterozygous
If the alleles for the inherited trait are different; one dominant and one recessive
Use a capital & lowercase letter (Tt)
Homozygous
If the alleles for the inherited trait are the same; both dominant or both recessive
Use two capital letters or two lowercase letters (TT, tt)
Genotype
The gene combination of an organism
TT, Tt, tt
Phenotype
The way that an organism looks
Tall/short

9. Dominant vs. Recessive

10. Genotypes vs. Phenotypes
HH or Hh (black hair)
hh (brown hair)
Phenotypes
Black (black hair)
Brown (brown hair)