Biology Chapter on Chromosomal Rearrangements

Mendel's Experiments and Heredity

• Genetics is the study of heredity.
• Mendel's work predated the discovery of chromosomes and genes.
• Mendel used a simple biological system (pea plants) and methodical quantitative analyses with large sample sizes.
• Mendel's work revealed fundamental principles of heredity.
• Genes, carried on chromosomes, are the basic units of heredity.
• Genes can be replicated, expressed, or mutated.
• Mendelian genetics is a starting point for understanding inheritance.
• Mendel's work was initially overlooked.
• The blending theory of inheritance was the dominant belief at the time.
• Mendel used a controlled breeding system with true-breeding pea plants.
• True-breeding plants always produce offspring that look like the parent.
• Mendel conducted hybridizations (mating different traits).
• Pollen, containing male gametes, is transferred to the stigma of a separate plant to produce hybrid offspring.
• Removing anthers prevents self-fertilization.
• P0 generation are the parental plants
• F1 generation are the first filial generation.
• F2 generation are the second filial generation.
• Mendel calculated ratios in his pea plant experiments.
• Ratios of offspring were roughly 3:1.
• Mendel observed clear characteristics in plants
  • flower color (violet vs. white)
  • flower position (axial vs. terminal)
  • plant height (tall vs. dwarf)
  • seed texture (round vs. wrinkled)
  • seed color (yellow vs. green)
  • pea pod size (inflated vs. constricted)
  • pea pod color (green vs. yellow)
• Observable physical traits in an organism is called the phenotype.
• The full set of genetic information is the genotype.
• Homozygous - an organism has two identical alleles for a trait.
• Heterozygous - an organism has two different alleles for a trait.
• Dominant allele - observable in hybrid offspring, masking the recessive allele.
• Recessive allele - only visible when paired with another recessive allele
• Punnett Square is a diagram to calculate the expected proportions in a monohybrid cross
• Test cross is used to determine the genotype of a dominant trait.
• In a test cross, the dominant organism is crossed with a homozygous recessive organism.

Alternatives to Dominance and Recessiveness

• Incomplete Dominance - heterozygotes have an intermediate phenotype (e.g., pink snapdragons).
• Codominance - both alleles are expressed simultaneously (e.g., MN blood types).
• Multiple Alleles - more than two alleles exist for a trait affecting a population (e.g., rabbit coat color).
• Lethal Alleles - a non-functional allele of an essential gene leading to death. This lethal form may either be dominant or recessive
• X-linked - genes located on the X chromosome
  • Males have one copy of any X-linked genes, meaning that the males are hemizygous for the X-linked characteristics
  • Males are more likely to express recessive X-linked disorders.

Epistasis

• Epistasis occurs when one gene masks the expression of another.
• It is defined in genetics to describe the interaction between two genes where one gene masks or modifies the effect of another
• Multiple genes contribute to observable characteristics

Test your knowledge on chromosomal structural rearrangements, transcription processes, and the roles of various RNA types in protein synthesis. This quiz covers key concepts from molecular biology, including definitions and processes related to DNA and RNA. Challenge yourself and see how well you understand these fundamental topics!