8.4- Punnett Squares

Punnett Square:

diagram to observe probabilities of offspring genotypes using the parent genotypes for a particular gene.

Experimental heredity:

crossing different organisms to observe phenotype ratios in offspring, which can be used to determine underlying genotypes.

P:

first, “parental” generation. Usually homozygous dominant (AA) x homozygous recessive (aa). •

F1:

first generation of offspring from breeding the P generation. “Filial 1st hybrid”. •

F2:

the generation of offspring resulting from breeding the F1 generation. “Filial 2nd hybrid”.

True breeding cross:

a cross between two homozygous parents, such that the offspring all share the same phenotype (e.g. crossing AA x aa parents always produces Aa offspring). 

Test Cross:

used to determine an unknown genotype by crossbreeding with a known (usually homozygous recessive) genotype. 

Monohybrid cross:

used to study inheritance of one set of alleles (e.g. pea color). a. E.g. Aa x Aa 2.

Dihybrid cross:

used to study inheritance of two sets of alleles (e.g. pea color and smooth vs wrinkled peas). a. E.g. AaBb x AaBb