Mendel studied seven specific traits present in two distinct forms in pea plants.
Looking at patterns of inheritance – offspring resembled in some traits.
For example – looking at purple vs white flowers – he made a “true-breeding” population
of each color by making several generations of offspring many from “self-fertilization”
(pollen from a plant was used to fertilize eggs from same plant). A true-breeding
population of white flowers will only ever give white flowers when bred among
themselves – likewise purple flowers only gave purple offspring.
1. These generations of true breeding plants made up what was called the P
(parental) generation and he cross – fertilized white plants with purple.
2. The resulting cross of two varieties is called a hybrid and this would be called the
F1 generation. (1st filial generation) – he discovered in every cross of two varieties
of traits – only one version of the trait showed up in all of the offspring. Purple X
White flowers yielded all purple flowers.
3. Now he took the F1 generation and self-fertilized them (all purple) and found both
purple and white flowers appeared in F2 generation.
When we talk about the inheritance of a single trait it is called a monohybrid cross.
Mendel’s Laws:
 There are multiple versions of genes for any particular trait and we call these
alleles.
 We have pairs of alleles for each trait (alleles are forms of genes, there are 1000s
of genes on each chromosome) – if both alleles are the same, the trait is
homozygous. If you have two versions of the allele, the trait is heterozygous.
 The allele that shows up most frequently and can mask the presence of the other
allele is called the dominant allele. The recessive allele only shows up in the
absence of the dominant allele.
 Making gametes allows one allele to be distributed for each gene to each sperm
and egg.
 Genotype is the genetic makeup of a trait and phenotype is the physical
appearance.