1. 3-3a. Genetics
Chapter 6.3 & 6.4

2. Mendel laid the groundwork for genetics.
(Don’t write this)
Mendel laid the groundwork for genetics.
Traits are characteristics that are inherited.
Ex. Right handed or left?
Genetics is the study of biological inheritance patterns and variation.
Gregor Mendel showed that traits are inherited as discrete units. (alleles)
Mendel’s Research that lead to today’s theories…….

3. Results: 100% purple offspring
Mendel used pea plants to research and discover genetics.
First he bred 2 purebred purple plants (P Generation)
Results: 100% purple offspring
Mendel controlled the
fertilization of his pea plants
by removing the male parts,
or stamens.
He then fertilized the female
part, or pistil, with pollen from
a different pea plant.

4. Results: 100% purple offspring (F1 Generation)
Then he bred a purebred Purple to a purebred White
( P generation)
Results: 100% purple offspring (F1 Generation)
Then he bred 2 F1 generation (purples)
Results: 75% Purple, 25% White (F2 Generation)

5. Mendel drew three important conclusions.
Traits are inherited as discrete units. (alleles)
Organisms inherit two copies of each gene, one from each parent.
The two copies segregate during gamete formation.
The last two conclusions are called the law of segregation.
purple
white

6. The same gene can have many versions. Example: Eye Color – Blue, Brown
A gene is a piece of DNA that directs a cell to make a certain protein.
Each gene has a locus, a specific position on a pair of homologous chromosomes.

7. An allele is any alternative form of a gene occurring at a specific locus on a chromosome.
Example: Dominant hand – Right or left
Each parent donates one allele for every gene.
You have 2 alleles for every gene
We use letters to symbolize alleles
Example: BB, Bb, or bb
The same letter represents that gene

8. Warning: Very Important Vocab coming up…..
Homozygous – When you have two alleles that are the same. (AA or aa)
Heterozygous - When you have two alleles that are different (Aa)

9. More very important Vocab.
A genotype refers to the makeup of a specific set of genes.
Your alleles that you inherited
A phenotype is the physical expression of a trait.
What you see

10. Yes you have more very important Vocab to learn
A dominant allele is expressed as a phenotype when at least one allele is dominant.
A recessive allele is expressed as a phenotype only when two copies are present.
Dominant alleles are represented by uppercase letters; recessive alleles by lowercase letters.

11. Example: Eye Color is B and b NOT B and g
(Don’t write this)
Tips when doing genetics
You can use any letter you want
Avoid letters like C, S, P, X, etc b/c their big letter looks the same as the little letter and it looks VERY confusing
When working with a one trait use one letter
Example: Eye Color is B and b NOT B and g
The different letter represents another trait

12. In cows, Black is dominant to Red
Let’s Practice…..
In cows, Black is dominant to Red
What is the genotype for a Red cow?
What is the phenotype for Bb?
What is the phenotype of a cow that is heterozygous?
What is the phenotype of a cow that is homozygous dominant?