Mendel's Experiments and Principles of Genetics

Gregor Mendel

Austrian monk who worked with pea plants and provided the foundation for modern genetics.

Model Organisms

Organisms that are used to study biological processes; Mendel chose pea plants as model organisms.

True-breeding

Organisms that will produce offspring identical to themselves if they self-pollinate; also known as 'purebred'.

Hybrid

The offspring of a cross between parents with different traits.

P Generation

The parents of a cross.

F1 Generation

The offspring of the P Generation; also known as 'first filial'.

F2 Generation

The offspring of the F1 Generation; also known as 'second filial'.

Cross

The mating of two organisms in genetics.

3:1 Ratio

The ratio of purple to white flowers observed in the F2 Generation after Mendel's experiments.

Genes

Factors that are passed from one generation to the next and determine inheritance.

Alleles

Different forms of a gene, such as brown eyes vs. blue eyes.

Principle of Dominance

Some alleles are dominant while others are recessive; dominant alleles will mask the recessive ones.

Principle of Segregation

Alleles will separate from each other during meiosis, ensuring each gamete receives only 1 allele.

Principle of Independent Assortment

Genes and the chromosomes they are attached to assort without influence on each other.

Pea Shape

One of the 7 traits Mendel followed; can be Round or Wrinkled.

Pea Color

One of the 7 traits Mendel followed; can be Yellow or Green.

Pod Shape

One of the 7 traits Mendel followed; can be Inflated or Constricted.

Pod Color

One of the 7 traits Mendel followed; can be Yellow or Green.

Flower Color

One of the 7 traits Mendel followed; can be Purple or White.

Flower Position

One of the 7 traits Mendel followed; can be Axial or Terminal.

Plant Height

One of the 7 traits Mendel followed; can be Tall or Dwarf.

Gene

A heritable factor that has a specific characteristic and a specific locus on a pair of homologs.

Alleles

Alternative forms of a gene

Dominant Allele

The allele that is expressed; usually represented by a capital letter

Recessive Allele

The allele that is only expressed if the dominant allele is absent; usually represented by a lowercase letter

Homozygous

Having 2 of the same allele; BB or bb; sometimes called 'purebred'

Heterozygous

Having 2 different alleles; Bb

Genotype

The genetic makeup of the organism; BB, Bb, or bb

Phenotype

The physical appearance of the trait; brown or blue eyes

Monohybrid Cross

A cross showing the inheritance of only one trait

Dihybrid Cross

A cross showing the inheritance of two traits

Genome

All the genetic material in an organism

Punnett Square

A grid system for predicting the possible genotypes that result from a cross; deals with probability

Testcross

A cross between an organism of unknown genotype with an organism of the recessive genotype; allows scientists to determine if the organism of unknown genotype is homozygous dominant or heterozygous

F1 Offspring

Offspring resulting from the first cross; used to determine genotypes and phenotypes

F2 Offspring

Offspring resulting from crossing two F1 individuals; used to determine genotypes and phenotypes

Phenotypic Ratio

The ratio of different phenotypes in the offspring

Genotypic Ratio

The ratio of different genotypes in the offspring

Segregation

The process by which alleles separate during gamete formation

Fertilization

The union of gametes to form a new organism

Mendel's Principles

Fundamental concepts that describe the inheritance of traits

Flower Color in Peas

Purple (P) is dominant to white (p)

Plant Height in Peas

Tall Plants (T) are dominant to Dwarf Plants (t)