Genetic Diversity
Genetic diversity
Genetic diversity is the variety of genes within a species, allowing for adaptation to environmental changes.
- Genetic diversity refers to the variety of genetic material within a population or species.
- It is the foundation of evolution and adaptation, enabling species to survive in changing environments.
Mutation
Mutation
A mutation is a random change in DNA that introduces new genetic variants (alleles).
- Mutation is a random, spontaneous change in the DNA sequence of an organism’s genome.
- It occurs naturally during DNA replication or due to environmental factors such as radiation, chemicals, or viruses.
- Mutations alter the sequence of nucleotide bases (A, T, C, G) in a gene.
- This change can produce a new version of a gene, known as an allele.
- Different alleles may result in new traits, some beneficial, others neutral or harmful.
- A mutation in the CCR5 gene in humans provides resistance to HIV infection.
- This advantageous allele spread through populations exposed to high viral pressure.
Types of Mutations
- Point mutations: A change in a single base pair (e.g., substitution).
- Insertion or deletion: Addition or removal of one or more bases, often causing a frameshift.
- Chromosomal mutations: Large-scale changes such as duplication, inversion, or translocation.
Although mutations occur randomly, natural selection determines which mutations persist in future generations.
TipMost mutations are neutral or harmful, but occasionally, a beneficial mutation provides a survival advantage that natural selection can act upon.
Sources of Mutations
- DNA replication errors: random copying mistakes.
- Radiation: ultraviolet or ionizing radiation can cause base changes.
- Chemical mutagens: such as tobacco smoke or pesticides.
- Viruses: can insert foreign DNA into the host genome.
Sexual Reproduction and Genetic Recombination
Genetic recombination
Genetic recombination refers to the random mixing of parental genes during meiosis and fertilization, creating genetically unique offspring.
- While mutation creates new alleles, sexual reproduction reshuffles existing alleles into new combinations, creating genetic recombination.
- This process occurs through three mechanisms:
- Independent assortment: During meiosis, chromosomes are randomly distributed to gametes.
- Crossing over: Homologous chromosomes exchange segments of DNA, creating unique allele combinations.
- Random fertilization: Any sperm can fuse with any egg, further increasing variation.
In humans, the combination of 23 chromosome pairs through meiosis and fertilization produces over 8 million possible genetic variations in offspring.
Advantages of Genetic Diversity
- Increased adaptability: Diverse populations survive better under environmental stress.
- Reduced inbreeding depression: Genetic variation prevents harmful alleles from accumulating.
- Disease resistance: Some individuals carry alleles providing immunity to emerging diseases.
Reproductive Isolation and Speciation
Reproductive isolation
Reproductive isolation is the prevention of gene flow between populations due to physical, ecological, or behavioral barriers.
- Reproductive isolation occurs when two populations of the same species can no longer interbreed to produce fertile offspring.
