Methods of Genetic Study: Experimental Breeding

Methods of Genetic Study

• Planned Experimental Breeding is the most direct method to study the mode of inheritance of a trait by mating individuals with contrasting expressions of the desired trait and observing their offspring through several generations.

Factors to Consider in Choosing a Test Organism

• The chosen organism should exhibit detectable differences in kinds of variations.
• The organism should have an effective means of combining parental traits through sexual reproduction or a system of recombination.
• Controlled mating is facilitated if the experimenter can choose parental lines.
• Short generation time allows for faster acquisition of results, made possible by organisms that require only a short time between generations.
• A large number of offspring enables the transmission of traits to obey statistical laws and approach ideal ratios.
• Organisms should be easy to care for, requiring minimum space, food, and time for caring.

Pedigree Analysis, Karyotyping, and Twin Study

• Pedigree Analysis is a method of studying genetics.
• Karyotyping is the analysis of an organism's chromosome composition, determining the normal chromosome number, establishing new species, and detecting chromosomal aberrations.
• A karyogram is a pictorial representation of an organism's chromosomes.
• Twin Study is a special statistical test that measures the degree of concordance or disconcordance between different kinds of twins.
• Concordance refers to both twins possessing or being free of a particular trait, while disconcordance occurs when only one twin possesses the trait.
• High concordance among identical twins reared apart suggests a greater role of genes than environment.
• Greater concordance between fraternal twins reared together suggests a greater role of the environment.

Types of Twins and their Significance

• Dizygotic twins have different DNA and are reared in the same environment; if they have the same intelligence, it is due to environment, and if they have different intelligence, it is due to genetics.
• Monozygotic twins have the same DNA and are reared in different environments; if they have the same intelligence, it is due to genetics, and if they have different intelligence, it is due to environment.