MCQ on Genetic Variation, Inheritance, and Cell Division

Genetic Variation

• Sources of genetic variation:

  • Mutations: changes in DNA sequence
  • Genetic recombination: crossing over and independent assortment during meiosis
  • Gene flow: movement of genes between populations

• Types of genetic variation:

  • Allelic variation: different forms of a gene, resulting in varying expressions of a single trait, such as different flower colors or blood types, which can provide a selective advantage or disadvantage in certain environments.

  : Allelic variation: multiple forms of a gene, such as different alleles of the ABO gene that determine an individual's ABO blood type, leading to variations in the expression of a single trait.

  • Genomic variation: differences in DNA sequence and structure
  • Epigenetic variation: chemical modifications to DNA or histone proteins

Genetic Inheritance

• Mendel's Laws:
  • Law of Segregation: each pair of alleles separates during gamete formation
  • Law of Independent Assortment: alleles for different genes are sorted independently
  • Law of Dominance: dominant alleles mask recessive alleles
• Patterns of inheritance:
  • Autosomal dominant/recessive traits
  • X-linked traits
  • Incomplete dominance and codominance

Chromosome Structure

• Chromatin:
  • DNA wrapped around histone proteins to form nucleosomes
  • Higher-order chromatin structures: chromatin fibers and chromonema
• Chromosome components:
  • Centromere: specialized region for chromosome segregation
  • Telomere: repetitive DNA sequences at chromosome ends
  • Origins of replication: sites for DNA replication initiation

Mitosis

• Stages:
  1. Interphase: chromatin condenses, spindle fibers form
  2. Prophase: chromatin condenses, nuclear envelope breaks down
  3. Metaphase: chromosomes align at cell equator
  4. Anaphase: sister chromatids separate
  5. Telophase: nuclear envelope reforms, chromatin decondenses
  6. Cytokinesis: cytoplasm divides, cell splits
• Importance:
  • Somatic cell division: replacement and growth
  • Produces genetically identical daughter cells

Meiosis

• Stages:
  1. Interphase: chromatin condenses, spindle fibers form
  2. Prophase I: chromatin condenses, homologous chromosomes pair
  3. Metaphase I: paired chromosomes align at cell equator
  4. Anaphase I: homologous chromosomes separate
  5. Telophase I: nuclear envelope reforms, chromatin decondenses
  6. Prophase II: chromatin condenses, spindle fibers form
  7. Metaphase II: sister chromatids align at cell equator
  8. Anaphase II: sister chromatids separate
  9. Telophase II: nuclear envelope reforms, chromatin decondenses
  10. Cytokinesis: cytoplasm divides, cell splits
• Importance:
  • Gamete formation: diversity and genetic variation

Sexual and Asexual Reproduction

• Sexual reproduction:
  • Involves meiosis and fertilization
  • Increases genetic variation
  • Examples: humans, animals, plants
• Asexual reproduction:
  • Involves mitosis
  • Produces genetically identical offspring
  • Examples: bacteria, some plants and animals