Core Concepts in Biological Reproduction and Genetics

Fundamentals of Biological Reproduction

Reproduction: The biological method necessary to ensure the survival of species.

Types of Reproduction

• Asexual Reproduction: Requires only one parent; creates exact genetic copies of itself; does not require gametes.

• Sexual Reproduction: Requires two parents who provide the gametes; descendants inherit characteristics from both parents.

Gametes and Gonads

Gamete: Specialized cells formed by meiosis from diploid cells in the gonads.

Reproductive Structures (Gonads)

• Unisexual: Characterized by two distinct types of individuals and gonads (Male and Female). Males and females exhibit traits that differentiate them (sexual dimorphism).

• Hermaphrodite: Individuals possess both male and female gonads.

Key Reproductive Processes

• Fertilization: The union of two gametes (Male and Female) that produces a zygote.

• Parthenogenesis: The development and birth of an individual from an unfertilized egg.

Core Concepts in Genetics and Heredity

Genetic Terminology

Genetics:

The science that studies the mechanisms of heredity and the laws by which they are governed.

Gene:

A specific DNA fragment that contains the necessary information to establish a hereditary character (trait).

Locus:

The fixed position occupied by a gene on a chromosome.

Alleles:

The different alternative forms that a gene may have for a particular character.

Allele Combinations

• Homozygous: When an individual's alleles for a specific gene are identical to one another.

• Heterozygous: When an individual's alleles for a specific gene are different.

Expression of Traits

Genotype:

The complete set of genes an individual possesses, inherited from their parents.

Phenotype:

The set of observable characteristics displayed by an organism, resulting from the interaction of genotype and environment.

Mendel's Laws of Inheritance

1. Law of Uniformity (F1 Hybrids)

   In a cross between two purebred lines that differ in a single trait, the resulting offspring (F1 generation) is uniform in phenotype and genotype.

2. Law of Segregation (F2 Generation)

   When F1 hybrids are crossed, the alleles separate (segregate) and are distributed to gametes independently, allowing recessive traits to reappear in the F2 generation.

3. Law of Independent Assortment

   The alleles for different traits are inherited independently of each other and combine at random in the offspring, provided the genes are located on different chromosomes.

Non-Mendelian Inheritance Patterns

• Incomplete Dominance (Intermediate Inheritance)

  Occurs when both alleles are expressed equally, resulting in a blending of information.

  Results: Heterozygotes display an intermediate phenotype between both parental characteristics.

• Codominance

  Occurs when both alleles are expressed simultaneously and distinctly for the same character.

  Results: Heterozygotes display the characteristics of both parents simultaneously (e.g., blood type AB).