2 possible "alleles" for each trait The combination one has (1 from mom, 1 from dad, is called your "genotype" . 2 matching alleles = "homozygous". 2 different alleles = "heterozygous". In heterozygous individuals, the allele that is "expressed" (seen in individual’s appearance) is the "dominant" alleleThe traits that are expressed make up your "phenotype". The allele that is not expressed is the "recessive" allele. There are more than 2 alleles for some traits. Most traits, in fact, are affected by more than 1 gene. Sex-Linked Traits- In the case of genes located on the X chromosome, females would have the usual 2 alleles for each gene but males only have 1 X chromosome and thus 1 allele (the Y chromosome contains only a small number of genes related to gender).
Punnett Square
The Punnett square is a summary of every possible combination of one maternal allele with one paternal allele for each gene being studied in the cross.
It is a diagram used to predict the traits of a genetic combination by combining dominant and recessive genes. They are squares with four squares in the middle and on top there can be say, gene B and B. Then on the left genes b and b. The upper case letters represent dominant genes while the lower case letters represent recessive genes. Then you combine the two pairs.
Pedigree Chart
A Pedigree Chart shows the distribution of particular traits within a family group.
A Pedigree Chart allows genetic traits (diseases and otherwise) to be traced back through families as well as to predict the occurrence of specific traits in potential future offspring.