Vocabulary for
Punnett Squares
In describing the
inheritance of genes,
some additional terms
are useful.
Phenotype



An organism’s Phenotype is the
physical appearance of a trait.
For example, in the “Class Traits”
activity, there were two possible
phenotypes for hair line-widows
peak or no widows peak.
For Mendel’s peas, the
phenotypes for seed shape
were round or wrinkled.
What are the two possible
phenotypes for earlobe style?
Allele



form of a trait
P or p
inside Easter egg
halves
Genotype
 Genotype
is the organism’s
allele combinations, or gene
type.
 There
are three possible
genotypes for chin shape—
CC, Cc, or cc.
Three additional terms can be
used to describe a genotype:



homozygous dominant = both genes
are dominant (ex: WW); called
Purebreds by Mendel.
homozygous recessive = both genes
are recessive (ex: ww); called
Purebreds by Mendel.
heterozygous = one dominant and one
recessive gene (ex: Ww); called Hybrids
by Mendel.
“Hard” Science Words
 By
now, you’ve probably
begun to recognize that
many “hard” science words
are made up of prefixes,
roots, and suffixes, and if
the word is broken down, the
meaning is easier to
remember.
For Example

In the words heterozygous and
homozygous the prefix “hetero”
means different; and the prefix
“homo” means same.
 So, heterozygous means there
are two different alleles;

homozygous means there are
two of the same alleles (either two
dominant or two recessive).