Offspring of inherit a pair of identical alleles for a trait

Offspring inherit a pair of nonidentical alleles for a trait

The allele that is always expressed

Capital letter

The allele that is masked or hidden

Lower case letter

Two alleles for a gene separate during gamete formation and end up in different gametes

Two phenotypes are both expressed at the same time in heterozygotes

Example: blood types

The presence of three or more alleles of a gene

Example: blood

Agglutinogens

(Antigens)

Agglutinins

(Antibodies)

Another antigen found on blood cells

Can be positive (it is present on cell)

or it can be negative (not present on cell)

• One alleles of a pair isn't fully dominant over its partner, so a heterozygous phenotype is between the two homozygous phenotypes
• Example: white flower crossed with red flower makes pink

• Two alleles of a gene may mask expression of another gene's alleles so some expected phenotypes may not appear at all
• Example: fur color of Labradors

• Expressions of the alleles at just a single location of a chromosome may have positive or negative effects on two or more traits
• Example: sickle-cell anemia

• The individuals of a population display a range of small differences in most traits
• Example: eye color