What are the four related concepts that make up Mendel's 3:1 inheritance pattern that he observed about the F2 offspring in his pea experiments?
1) Alternative versions of genes account for variations in inherited characters.
The gene for flow color existed in two versions (purple and white). These alternative versions of a gene are called alleles.
2) For each character, an organism inherits two alleles, one from each parent.
Each somatic cell in a diploid organism has two sets of chromosomes, one set inherited from each parent. Thus, a genetic locus is actually represented twice in a diploid cell, once on each homolog of a specific pair of chromosomes. The two alleles at a particular locus may be identical, as in the true-breeding plants of Mendel's P generation. Or the allels may differ, as in the F1 hybrids.
3) If the two alleles at a locur differ, then one, the dominant allele, determines the organism's appearance; the other, the recessive allele, has no noticeable effect on the organism's appearance.
Mendel's F1 plants had purple flowers because the allele for that trait is dominant and the allele for white flowers is recessive.
4) The law of segregation: The two alleles for a hertiable character segregate (separate) during gamete formation and end up in different gametes.
An egg or a sperm gets only one of the two allels that are present in the somatic cells of the organism making the gamete. If an organism has identical alleles for a particular character (true-breeding) then that allele is present in all gametes. If different alleles are present, as in F1 hybrids, 50% of the gametes receive the dominant allele and 50% receive the recessive allele.