Teacher As ScholarPunnett Square:

Key Terms

Allele:One member of a pair of

genes occupying a specific spot on a chromosome that

controls the same trait.

Chromosome:A structure within the cell that bears

the genetic material of an organism.

Codominance:

A condition in which the alleles of a gene pair in a heterozygote

are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive.

Example: AB Blood Type

Dominant Allele:

The allele that determines the phenotype of an

organism, masking the effect of the recessive allele when present.

Gamete:A reproductive

cell that contains the haploid set of chromosomes.

Gene:A segment of DNA that is responsible

for the phenotype of an organism.

Genotype:The entire set of genes

in an organism that determines the expression of a

particular phenotype.

Heredity:The passing of

genetic factors from parent to offspring.

Heterozygous:An organism containing two different alleles (a dominant

and a recessive) for a particular trait.

Homozygous:An organism containing two copies of the same

allele (two dominant or two recessive) for a particular

trait.

Homozygous Dominant:An organism that

has two dominant alleles (RR).

Homozygous Recessive:

An organism that has two recessive

genes (rr).

Incomplete Dominance:A kind of dominance occurring in

heterozygotes in which the dominant allele is only partially expressed. This usually results in offspring with an intermediate

phenotype because the organism has one dominant allele and one

recessive allele.

Genetic Locus: The location of a

gene on a chromosome.

Monohybrid Cross:

A crossbreeding experiment that follows the inheritance of a single characteristic across one or more generations. In other words this is a cross of one trait from two parents.

Multiple alleles: The existence of

several known alleles of a gene.

Phenotype:The physical

appearance of an organism as a result of the interaction of its genotype and the

environment.

Polygenic Trait: A trait that is controlled by two

or more genes at different loci on different chromosomes.

Examples: height, skin color, weight.

Recessive:An allele whose phenotypic expression is masked by a

dominant allele. The recessive trait may be expressed when the

recessive genes are in a homozygous condition.

Trait:A qualitative

characteristic. An attribute of

phenotype, not of genotype.