Living Environment Translated Arabic 2014 | Page 58

 Punnett Square: a grid system used to predict all of the possible
genotypes resulting from a cross between two parents.
o An uppercase letter (capital) is used to represent the dominant
allele. ( Ex: G= green)
o The lowercase letter of the dominant allele is used to
represent the recessive allele. ( Ex: g=yellow)
o The genotype ( genetic makeup) are represented by a letter
code.
 GG- homozygous dominant
 gg- homozygous recessive
 Gg- heterozygous
o The phenotype is the way the organisms looks as a result of
the genotype.
 GG- looks dominant ( green)
 gg- looks recessive (yellow)
 Gg- looks dominant( green)
 Principles of Heredity:
o Traits are controlled by alleles on chromosomes.
o An allele’s effect is dominant or recessive.
o When a pair of chromosomes separate during meiosis, the
different alleles for a trait move into separate sex cells.