1. Mendel’s Laws of Heredity
Spring 2017

2. What are different forms of genes called?
Question
What are different forms of genes called?
Answer:
Alleles

3. Mendel’s Laws of Heredity
Mendel concluded that:
Biological inheritance is determined by factors.
Factors are passed from one generation to the next.
These factors that determine traits are called genes.

4. Mendel’s Laws of Heredity
Alleles are different forms of genes.
Example:
A gene for height can produce
genes for tall plants
genes for short plants

5. Mendel’s 1st Law of Heredity
Law of Segregation
Every organism has two alleles of each gene
When gametes are produced, the alleles separate.
RECALL gametes are male and female sex cells

6. Mendel’s Laws of Heredity
Phenotype
The way an organism looks and behaves.
Its what an organism PHYSICALLY looks like.
Examples:
Tall or short plants
Purple or white flowers
Green or yellow peas
Round or wrinkled seeds

7. Mendel’s Laws of Heredity
Genotype
The allele combination of an organism
Letter representation of alleles
3 ways to write a genotype:
2 capital letters
1 capital letter, 1 lower case
2 lower case letters

8. Mendel’s Laws of Heredity
An organism is homozygous for a trait if the two alleles for the trait is the SAME
TT- homozygous dominant
tt- homozygous recessive
Tt- heterozygous
(homo means the same, hetero means different.)

9. Mendel’s 2nd Law of Heredity
Law of Independent Assortment-
Genes for different traits are inherited independently of each other.
Alleles for a trait separate when gametes are formed.
In a dihybrid cross (two traits) you can see both of Mendel’s laws at work.

10. Heredity