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Scientific study of heredity; transmission of traits from parents to offspring.


A specific characteristic.


Section of DNA that determines a trait.


Alternative forms of a gene.


An allele that expresses its phenotypic effect even when heterozygous with a recessive allele.


An allele whose phenotypic effect is not expressed in a heterozygote. It is only expressed when homozygous.


Process of sexual reproduction in which male and female reproductive cells join to form a new cell.


Sex cell involved in sexual reproduction.


Fertilized egg formed during the fusion of gametes during sexual reproduction.


Fertlization in plants.

True breeding

The term used describe organisms that produce offspring identical to themselves if allowed to self-pollinate (homozygous).


Offspring formed of crosses between parents with different traits.


Separation of alleles during gamete formation.

Principle of Dominance

Some alleles are dominant, some are recessive (in Mendalian genetics).

Principle of Segregation

In most sexually reproducing organisms, each adult has two copies of a gene--one from each parent. These genes are segregated from each other when gametes are formed.

Principle of Independent Assortment

Genes for different traits can segregate independently during formation of gametes.


Likelihood that a particular event will occur; used to predict outcomes of genetic crosses.

Punnett Square

Diagram showing the gene combinations that might result from a genetic cross.


Term used to describe an organism that has two identical alleles for a particular trait.


Term used to describe an organism that has two different alleles for a particular trait.


Genetic make up of an organism.


Physical characteristics of an organism; determined by genotype.

Dihybrid Cross

Hybridization using two traits with two alleles each.

Monohybrid Cross

Hybridization using a single trait with two alleles.

P1 Generation

Parent generation.

F1 Generation

First filial generation; offspring of the cross of a P1 generation. (children)

F2 Generation

Second filial generation; offspring of the cross of a F1 generation. (grandchildren)

Incomplete Dominance

Situation in which one allele is not completely dominant over the other.


Situation in which both alleles of a gene contribute to the phenotype of an organism.

Multiple Alleles

Three or more alleles of the same gene.

Polygenic Traits

Trait controlled by two or more genes.

Sex-linked Gene

Gene located on the X or Y chromosome

Sex-linked Trait

A trait that is carried on the X chromosome and has no allele on the Y chromosome

Male Gamete

Sperm cell

Female Gamete

Egg cell

Gregor Mendel

Father of genetics; scientist who followed the scientific method when designing genetic experiments.


Possible explanation for a set of observations or answer to a question; accepted or rejected, can not be proven; must be testable

Manipulated (Independent) Variable

Factor in an experiment that a scientist purposely changes to cause an effect; on x-axis

Responding (Dependent) Variable

Factor in an experiment a scientist wants to observe; on y-axis

Constant (Control) Variables

All factors in an experiment that are kept the same and have a fixed value

Control Group

The group that will not be affected by the experimental variable; is used as a standard of comparison in an experiment

Experimental Group

The group that receives experimental treatments

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