Biology Cheat Sheet: Cell Cycle & Division

Interphase

• Phases: G1, S, G2
• Activities: Cell grows, replicates DNA, prepares for division.

Mitosis (PMAT)

• Prophase: Chromosomes condense.
• Metaphase: Chromosomes line up.
• Anaphase: Sister chromatids split.
• Telophase: Nuclei reform.

Cytokinesis

• Process: Cytoplasm splits.
  • In Animals: Formation of cleavage furrow.
  • In Plants: Formation of cell plate.

Purpose of Mitosis

• Multicellular organisms: Growth and repair.
• Unicellular organisms: Reproduction.
• Outcome: Produces 2 diploid daughter cells.

Meiosis

• Process: Two divisions result in four haploid gametes.
• Genetic Diversity: Achieved through crossing over during Prophase I.

Genetics

Chromosome Structure

• Components: Chromatid, centromere.
• Homologous Pair: One chromosome from each parent.

Alleles

• Types: Dominant (A), Recessive (a).
• Combinations: Homozygous (AA, aa), Heterozygous (Aa).

Genotype vs Phenotype

• Genotype: Genetic makeup.
• Phenotype: Physical trait.

Inheritance Patterns

• Incomplete Dominance: Blending of traits (e.g., red + white = pink).
• Codominance: Both traits show (e.g., AB blood).
• Sex-linked (X-linked): Traits affect males more.

Mendel's Laws

• Law of Segregation: Alleles separate during gamete formation.
• Law of Independent Assortment: Traits are inherited independently.

Central Dogma & Protein Synthesis

Process

• DNA to RNA to Protein

Transcription

• Location: Nucleus
• Process: DNA is transcribed to mRNA.

Translation

• Location: Ribosome
• Process: mRNA is translated to amino acids.
• Components:
  • mRNA: Messenger.
  • tRNA: Carries amino acids.
  • rRNA: Part of the ribosome.
• Codon: mRNA triplet.
• Anticodon: tRNA match to codon.

Evolution & Natural Selection

Natural Selection

• Principle: Best traits enhance survival and reproduction.

Adaptation

• Definition: Heritable trait that improves fitness.

Mutation

• Definition: Random DNA change leading to variation.

Sexual Selection

• Definition: Traits that improve mating success.

Speciation

• Example: Populations split (e.g., Galapagos finches).

Terminology

• Homologous Structures: Same structure, different function.
• Analogous Structures: Same function, different origin.
• Vestigial Structures: Reduced function.

Ecology

Food Chain/Web

• Concept: Energy flow through trophic levels.
• 10% Rule: Only 10% of energy is transferred up each level.

Trophic Levels

• Sequence: Producer -> Primary Consumer -> Secondary Consumer -> Tertiary Consumer.

Symbiosis

• Mutualism: Both species benefit.
• Commensalism: One benefits, other unaffected.
• Parasitism: One benefits, one harmed.

Population Dynamics

• Growth Models:
  • Exponential Growth: J-curve.
  • Logistic Growth: S-curve.
• Carrying Capacity (K): Maximum sustainable population size.
• Density-Dependent Factors: Resources like food and disease.
• Density-Independent Factors: Environmental factors like weather and disasters.

Bonus Quick Facts

• Diploid (2n): Full set of chromosomes (body cells).
• Haploid (n): Half set of chromosomes (gametes).
• Zygote: Fertilized egg; a diploid cell.
• Monomer/Polymer Examples:
  • Nucleotide/DNA
  • Amino acid/Protein
• DNA Base Pairing: A-T, C-G; RNA: A-U, C-G.