Unit 5Vocabulary

Heredity (p 115):  The passing of genetic traits from parents to offspring

Gene:  A set of instructions that control inherited traits

Alleles (p 120):  An allele is one member of a pair of genes that is located at a specific position on a specific chromosome.  Organisms have two alleles for each trait.  Individual alleles control inheritance of traits.  Some alleles are DOMINANT and some alleles are RECESSIVE

Genetics:  The study of how traits are inherited through the actions of alleles.

Dominant Trait (p 117):  The trait observed in the 1st generation when parents that have different traits are bred.

Recessive Trait (p 117):  A trait that reappears in the 2nd generation after disappearing in the 1st generation when parents with different traits are bred.

Homozygous:  Having identical alleles for a single trait. 

Heterozygous:  Having two different alleles for a single trait. 

Purebred: producing the same offspring with the same form of the trait as the parent

Example:  Purebred short pea plants produce short offspring.  Purebred offspring are IDENTICAL to parents.  To produce purebred plants, Mendel allowed peas with one particular trait to self-pollinate. 

Hybrid: Having 2 different alleles for each trait.  In a hybrid, the recessive allele is “hidden” and the dominant allele is what we see.

Example:  Mendel crossed two purebred pea plants, one purebred tall and one purebred short.  The result was a hybrid TALL. 

Phenotype:  An organism's appearance or other detectable characteristics (PHYsical Feature=PHEnotype)

Genotype:  The entire genetic makeup of an organism; also the combination of genes for one or more specific traits (Example:  the genotype of a tall plant might be Tt or TT)

Probability:  The likelihood that a possible future event will occur in any given instance of the event.

Punnett Square:  A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine.

Incomplete Dominance:  Production of a phenotype that is intermediate between the two homozygous parents.