1.The heritable "factor" for each trait can exist in alternative forms, each specifying one of the traits of an observable character (phenotypes). heritable factors are genes.
Each gene can exist in alternative forms called alleles.
For example, any particular copy of the seed color gene could be the allele that specifies yellow or the allele that specifies green.
2. An organism contains two alleles of a gene for each trait.
We now know that these two alleles are a direct consequence of organisms being diploid, that is, carrying two homologous chromosomes each with one copy of that gene.
The genotype of an organism, that is the allele makeup, may consist of the same allele, a condition called homozygous, or different alleles, a condition called heterozygous.
3.The Law of Dominance states that if the two alleles for a particular gene differ, only the dominant allele will actually control the trait.
As a result, the recessive allele will be "masked."
In modern terminology, we would say that in heterozygous individuals the dominant allele determines the phenotype, or physical appearance of an organism
4.The Law of Segregation states that the two copies of the gene for each trait segregate (or separate) from one another during transmission to the offspring.
This law implies that gametes have only one copy of every gene (are haploid).
This law is a direct consequence of the separation of homologous chromosomes during meiosis.
This law also implies that heterozygous individuals can make two kinds of gametes, one with a dominant allele and one with a recessive allele.
5.The Law of Independent Assortment states that the alleles of different traits assort independently of one another during transmission to the offspring.
During gamete formation the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair
All possible allelic combinations are made
This law is a direct consequence of the independent assortment of chromosomes during Meiosis.