Mendel’s Laws

Mendel

Gregor Mendel was an Autrian monk who looked at heredity patterns in pea plants. He noticed that the pea plants had varying characteristics: round peas, wrinkled peas, green or yellow peas, different flower colors and different pod colors. He also noticed that when he crossed certain plants he ended up with a variety of results.

Please read pages 130-132 for a detailed outline on his experiments.

From his experiments Mendel devised a few laws of inheritance.

The first set of laws is the Law of Segregation

1. For each trait an organism has two hereditary factors called genes
   
2. Alternate forms of the gene are called alleles
   
3. The two alleles separate during meiosis and only one is passed on the gamete
   
4. The two gametes unite during fertilization to produce an offspring with two genes
   
5. If the two alleles differ, the phenotype will reflect the dominant allele
   
6. Not all genes have dominant and recessive alleles.
   

The second set of laws is the Law of Independent Assortment

1. The inheritance of one gene does not normally affect the inheritance of another gene
   

Some genes are linked to other genes. For instance, recessive genes found on the X chromosome will cause a recessive trait in a male but will only cause a recessive trait in a female if she is homozygous recessive.