Genetics lec 1

Genetics

The branch of biology dealing with the structure, organization, transmission, and function of genes, as well as the origin of variation. Simply put, it is the study of heredity (passing traits from parents to offspring) and variation (differences among individuals). 

Cytogenetics

Studies the physical basis of inheritance, focusing specifically on chromosomal structures and their effects. 

Molecular Genetics

Focuses on genomics and proteomics at the molecular level. 

Phylogenetics

Analyzes evolutionary similarities and differences among organisms.

Developmental Genetics

Examines genetic control over growth and development (e.g., control by hox genes). 

Behavioral Genetics

Explores the interaction between genetic inheritance and environmental influences on behavior. 

Sexual Reproduction

Occurs when a sperm cell fertilizes an egg cell to form offspring. 

Asexual Reproduction

Occurs when a single organism reproduces on its own to produce offspring. 

Gene

Coined by Wilhelm Johannsen (1909); the basic unit/determining factor of heredity made of a distinct nucleotide sequence.

Locus

The specific physical position or location of a gene on a chromosome.

Allele

alternate forms of a gene that control contrasting characteristics of the same trait.

Dominant Allele

Expresses its phenotype whenever present (both in homozygous ⁠TT⁠ and heterozygous ⁠Tt⁠ states).

Recessive Allele

Expresses its phenotype only in the absence of a dominant allele (homozygous recessive state, e.g., ⁠tt⁠).

Genotype

The underlying genetic makeup/constitution of an organism (e.g., ⁠TT⁠, ⁠Tt⁠, or ⁠tt⁠).

Phenotype

The observable physical features or traits produced by the genotype and its interaction with the environment.

Homozygous

Having two identical alleles at a locus on homologous chromosomes (e.g., ⁠TT⁠ or ⁠tt⁠).

Heterozygous

Having two different alleles at a locus on homologous chromosomes (e.g., ⁠Tt⁠).

Hemizygous

A condition where a gene is present in only one copy (e.g., genes on the X or Y chromosome in human males, who have XY).

Monohybrid Cross

A genetic cross involving individuals heterozygous for one pair of alleles (e.g., Tall \times Dwarf). 

Dihybrid Cross

A genetic cross involving individuals heterozygous for two pairs of alleles (e.g., Yellow Round Seed \times Green Wrinkled Seed). 

Test Cross

A diagnostic cross where an F1 progeny (or organism with an unknown dominant phenotype) is crossed with a double recessive parent to determine its genotype. 

F1 Generation

The first generation of offspring resulting from hybridization. 

F2

The offspring resulting from selfing/crossing the F1 hybrids or crossing an F1 hybrid with parents.