Mendelian Genetics or Transmission Genetics

Genes

Inherited characteristics are under the control of particulate factors.

Genes

Transmitted from one generation to another by vehicles called chromosomes.

Chromosomes

Vehicles that transmit genes from one generation to another.

Crosses (Mating)

Affected by chance deviation and evaluated using statistical analysis.

Human Traits

Initially studied using pedigrees.

Gregor Johann Mendel

Performed first set of hybridization experiments with garden pea.

1865

Mendel first reported the results of simple genetic crosses between strains of garden peas.

Mendel’s Experimental Approach

Chose an organism that was easy to grow and hybridize artificially. Easy to cross-breed during experiments.

Phenotype

Physical appearance of a trait in an individual.

Genotype

Genetic makeup of an individual whether it is diploid or haploid.

Allele

Alternative forms of a single gene.

Homozygous

When both alleles are the same.

Heterozygous

When the alleles are different.

Character

Heritable feature

Trait

Variant of a character

Parental Generation

P

First Filial Generation

F1

Second Filial Generation

F2

Monohybrid Cross

Only involves one pair of contrasting traits.

Reginald C. Punnet

Developed the Punnet Square in 1967

Male Parent

X-axis / Horizontal column

Female Parent

Y-axis / Vertical Column

Unit Factors in Pairs

Genetic characters are controlled by unit factors that exists in pairs in individual organisms.

Concept of Dominance and Recessiveness

When two unlike unit factors responsible for a single character are present in a single individual, one unit factor is dominant to the other, the recessive one.

Segregation

During the formation of gametes, the paired unit factor separate or segregate randomly so that each gamete receives one or the other.

Test Cross

An organism expressing a dominant phenotype but unknown genotype. Crossed with homozygous recessive individulal.

Dihybrid Cross

Uses two characters that are under study.

Independent Assortment

During gamete formation, segregating unit factors assort independently of each other.

Trihybrid Cross

Apply to three pairs of contrasting traits. Also referred to as three-factor cross.

Human Pedigrees

The pattern of inheritance of a specific type of phenotype can be studied even in humans.