Parental or Homozygous or "Pure-breeding" Strains.
Parental strains are defined as "pure-breeding" strains. This implies that they are homozygous for the alleles associated with a particular phenotype or phenotypes.
In Mendel's pea plants, for example, Purple flowers were dominant to white flowers. The Purple allele can be designated as A and the white allele can be designated as a. The corresponding Parental lines would have the following genotypes.
If there are more than two traits being considered at one time, then the parental lines are homozygous for all contrasting pairs of traits.
|Example -Two Traits||Consider two different genes A and B each with two alleles
(A or a and B or b). There are four possible
homozygous genotypes and two pairs of parental lines.
Pair 1: AABB and aabb and
Pair 2: aaBB and
|Example -Three Traits||With three different genes A, B and C each with two
alleles (A or a and B or b and
C or c ), there are eight possible homozygous genotypes and
four pairs of parental lines:
FAQ: Where do the parental lines come from?
Answer: Parental lines are "constructed" by geneticists through a series of matings or crosses. With some genes and some organisms this might be quite easy. With other genes and other organisms this might be quite difficult and take years. More information on parental lines can be obtained from links 2, 3 and 4 below.
|How to Obtain a Parental Line a) Autosomal Trait b) Sex-linked XX-XY c) sex-linked ZZ-ZW||2|
How to Obtain a Parental Line for a Dominant Allele
a) Autosomal Trait b) Sex-linked XX-XY c) sex-linked ZZ-ZW
|How to Breed a Homozygous Line for more than one gene||4|
Mendelian Genetics Index