Meiosis and Genetic Diversity Flashcards

Meiosis and Genetic Diversity

• Heritable information is essential for continuity of life and genetic diversity.
• Meiosis produces haploid gametes in sexually-reproducing diploid organisms, halving the chromosome number.
• Two sequential phases characterize meiosis: meiosis I and meiosis II.
• Mitosis and meiosis share similarities in chromosome segregation but diverge in daughter cell quantity and genetic content.

Role of Meiosis in Genetic Inheritance

• Chromosome replication and separation during meiosis contribute to genetic inheritance.
• Homologous chromosome pairs, containing one chromosome from each parent, are crucial in diploid cells.
• Sister chromatids, created during DNA replication, are identical unless replication errors occur.
• Tetrad formation during prophase I allows crossing over, increasing genetic variation within gametes.

Asexual vs. Sexual Reproduction

• Asexual reproduction involves one parent, producing genetically identical offspring.
• Genetic differences in asexual offspring arise only from mutations during DNA replication.
• Sexual reproduction, involving two parents, results in genetically diverse offspring with unique traits due to allele combinations.

Gametes and Chromosomal Composition

• Gametes (sperm and eggs) are haploid with 23 unpaired chromosomes in humans.
• Somatic cells are diploid, consisting of two paired chromosome sets, totaling 46 chromosomes in humans.

Chromosome Mechanics

• Homologous chromosomes carry genes for the same traits, inherited from both parents.
• Sister chromatids are identical and remain connected until separated during mitosis or meiosis II.

Genetic Variation Mechanisms

• Independent assortment during metaphase I randomly distributes maternal and paternal chromosomes to daughter cells, producing a mix of genetic combinations.
• In humans, each gamete can represent approximately 8.4 million possible chromosome combinations due to independent assortment.
• Crossing over in prophase I allows for DNA exchange between sister chromatids, creating new gene combinations and increasing genetic diversity.

Recombinant Asci in Sordaria fimicola

• The fungus Sordaria fimicola illustrates genetic variation through haploid cells undergoing meiosis after mycelial fusion.
• Crossing over observed in the resulting asci leads to diverse patterns of spore colors.

Evolutionary Implications

• Genetic variation generated during sexual reproduction is fundamental for species survival and adaptation.
• Natural selection favors variations better suited to environmental changes, enhancing population resilience.

Important Figures and Statistics

• Independent assortment allows for 2^n combinations, where n is the number of haploid chromosome sets.
• In humans, with 23 chromosomes, the possible gamete combinations is 2^23 (~8.4 million).
• Crossovers increase the potential combinations even further during meiosis.
• Fertilization introduces additional variability, creating zygotes with approximately 70 trillion diploid combinations.

Summary on Genetic Diversity

• Mechanisms contributing to genetic variation include independent assortment, crossing over, and random fertilization.
• These processes ensure that offspring inherit unique combinations of traits from both parents, essential for the survival of species in changing environments.

Explore key concepts related to meiosis and its role in genetic diversity through this set of flashcards. Understand the enduring principles and essential knowledge that underpin the process of meiosis in sexually-reproducing organisms.