diploid
having two copies of every chromosome
gametes
specialized reproductive cells that carry one copy of each chromosome (that is, they are haploid). Sperm are male gametes; eggs are female gametes.
genotype
the particular genetic makeup of an individual
haploid
having only one copy of every chromosome
homologous chromosomes
a pair of chromosomes that both contain the same genes. In a diploid cell, one chromosome in the pair is inherited from the mother, the other from the father.
meiosis
a type of cell division that generates genetically unique haploid gametes
phenotype
the visible or measurable features of an individual.
carrier
an individual who is heterozygous for a recessive allele and can therefore pass it on to offspring without showing any of its effects.
punnett square
a diagram used to determine probabilities of offspring having particular genotypes, given the genotypes of the parents.
dominant allele
an allele that can mask the presence of a recessive allele.
recessive allele
an allele that reveals itself in the phenotype only if a masking dominant allele is not present.
heterozygous
having two different alleles for a given gene
homozygous
having two identical alleles for a given gene
embryo
an early stage of development reached when a zygote undergoes cell division to form a multicellular structure.
zygote
a diploid cell that is capable of developing into an adult organism. The zygote is formed when a haploid egg is fertilized by a haploid sperm
independent assortment
the principle that alleles of different genes are distributed independently of one another during meiosis.
recombination
an event in meiosis during which maternal and paternal chromosomes pair and physically exchange DNA segments.