Mendel's Laws of Inheritance and Genetic Principles

Selective Breeding

Farmers: selective breeding of plants to improve crops.

Particulate Inheritance

Parental determinants are distinct.

Blending Inheritance

Parental determinants get mixed or blended during fertilization.

Gregor Mendel

Austrian Monk, scientist, mathematician, and gardener known as the Father of Genetics.

True-Breeding Plants

Plants that produce offspring identical to themselves when self-fertilized.

F1 Generation

The offspring of the parental generation in Mendel's experiments.

F2 Generation

The offspring of the F1 generation in Mendel's experiments.

Dominant Trait

The trait that appears in the F1 generation.

Recessive Trait

The trait that disappears in the F1 generation but appears in the F2 generation.

3:1 Ratio

The ratio of dominant to recessive traits observed in the F2 generation.

Genes

Hereditary determinants for a trait.

Alleles

Different versions of a gene.

Homozygous

An individual with two copies of the same allele (e.g., AA or aa).

Heterozygous

An individual with two different alleles (e.g., Bb).

Genotype

The combination of alleles found in an individual.

Phenotype

The expressed or measurable trait of an individual.

Law of Segregation

The two alleles in a pair segregate from each other during gamete formation.

Monohybrid Cross

Offspring of crosses between organisms differing in one character.

Punnett Square

A diagram used to predict genotypes and phenotypes of offspring from genetic crosses.

Dihybrid Cross

A genetic cross that examines the inheritance of two different traits.

Law of Independent Assortment

Each pair of alleles segregates independently of the segregation of other allele pairs.

Multiplication Rule

The probability of two independent events occurring at the same time is found by multiplying the individual probabilities.

Addition Rule

The probability of two mutually exclusive events occurring at the same time is found by adding the individual probabilities.

Quantitative Trait

A trait that occurs in a range (e.g., height).

Discrete Trait

A trait that occurs in two or a few different categories (e.g., eye color).

Garden Pea

The plant chosen by Mendel for his experiments due to its ideal characteristics.

Short Generation Time

A characteristic of the garden pea that allowed for quicker observation of traits.

Careful Record Keeping

One of the key qualities of a first-rate scientist demonstrated by Mendel.

Analytical Mind

A quality that enabled Mendel to effectively study inheritance.

Probability of Offspring

Likelihood of specific genetic combinations in offspring.

Multiple Alleles

More than two alleles exist for a gene.

Codominance

Both alleles express equally in heterozygotes.

Incomplete Dominance

Heterozygote shows intermediate phenotype.

Epistasis

One gene's expression affects another gene's expression.

Polygenic Inheritance

Multiple genes influence a single phenotype.

Crossing Over

Exchange of genetic material during meiosis.

Linkage

Tendency of genes to be inherited together.

Sex-linked Inheritance

Traits determined by genes on sex chromosomes.

X-linked Genes

Genes located on the X chromosome.

Y-linked Genes

Genes located on the Y chromosome.

Aneuploidy

Abnormal number of chromosomes in a cell.

Monosomy

Condition of having one less chromosome (2n-1).

Trisomy

Condition of having one extra chromosome (2n+1).

Polyploidy

Having an entire extra set of chromosomes.

Klinefelter Syndrome

XXY condition, phenotypically male with abnormalities.

Turner Syndrome

XO condition, phenotypically female with underdevelopment.

Deletion

Loss of a chromosomal segment.

Duplication

Repetition of a chromosomal segment.

Inversion

Reversal of a chromosomal segment's orientation.

Translocation

Movement of a chromosomal segment to another chromosome.

Philadelphia Chromosome

Translocation associated with chronic myelogenous leukemia.

Drosophila melanogaster

Model organism for studying genetics.

Barr Body

Inactivated X chromosome in female mammals.

Carrier

Individual with one copy of a recessive allele.

Hemizygous

Having only one allele for a gene.