Genetics, Evolution, and Biology: Key Concepts

Posted on Feb 16, 2025 in Biology

Genetics and Inheritance Patterns

If most males (squares) in a pedigree are affected, the disorder is likely X-linked. If there’s a roughly 50/50 ratio between affected men and women, the disorder is likely autosomal. If a disorder is dominant, at least one parent must have the disorder. If a disorder is recessive, neither parent has to exhibit the trait.

Cell Division: Mitosis

Mitosis Stages:

  • I (Interphase): Distinct nucleus, normal cell components.
  • P (Prophase): Nuclear membrane breaks down, chromosomes condense, spindles form.
  • M (Metaphase): Chromosomes align along the equator of the cell.
  • A (Anaphase): Chromatids migrate to opposite poles.
  • T (Telophase): Two new nuclei form, chromosomes decondense.
  • C (Cytokinesis): Cytoplasm divides, resulting in two new cells.

Blood Types and Inheritance

Blood Type Genotypes and Possible Recipients:

  • A: IAIA or IAi, can receive from A or O.
  • B: IBIB or IBi, can receive from B or O.
  • AB: IAIB, can receive from A, B, AB, or O.
  • O: ii, can receive from O only.

Allele Frequencies and Population Genetics

Hardy-Weinberg Equilibrium:

p2 + 2pq + q2 = 1

  • q2 is the percentage of the recessive phenotype.
  • 2pq is the percentage of the heterozygous population.
  • p2 is the percentage of the homozygous dominant population.
  • q2 is the percentage of the homozygous recessive population.

Protein Synthesis: Translation

  1. mRNA binds to the ribosome.
  2. mRNA advances until AUG (start codon) is at the P site.
  3. tRNA binds to the codon at the A site, bringing the appropriate amino acid.
  4. A peptide bond forms between the two amino acids.
  5. Elongation: P site tRNA moves to the E site, A site tRNA moves to the P site.
  6. The process repeats.
  7. tRNA at the E site is ejected.
  8. Continues until a stop codon is reached.
  9. Release protein.

DNA to RNA: Transcription

  1. RNA polymerase binds at the promoter region of the gene.
  2. DNA unzips.
  3. RNA polymerase moves forward until it reaches the coding region.
  4. RNA polymerase produces RNA complements (5′ to 3′) on the template strand.
  5. The process continues until a termination sequence is reached.
  6. Forms a hairpin loop.
  7. RNA is released.
  8. RNA gets edited: introns are removed, and exons are spliced together to form functional mRNA, all done by snRNPs.

Circulatory System Pathway

Vena Cava → Right Atrium → Valve → Right Ventricle → Valve → Pulmonary Artery → Smaller Artery → Arterioles → Lung Capillaries → Venules → Larger Veins → Pulmonary Vein → Left Atrium → Valve → Left Ventricle → Valve → Aorta → Body → Smaller Arteries → Arterioles → Capillaries of Body → Venules → Large Veins

Respiratory System: Gas Exchange Pathway

Nostrils → Nasal Cavity → Larynx → Pharynx → Trachea → Bronchi → Bronchioles → Alveoli

Blood Clotting Cascade

Thromboplastin activates prothrombin, which is converted to thrombin, which activates fibrinogen, which is converted into fibrin, forming a clot.

Primordial Earth Conditions

  • Highly Energetic: High temperature, UV Radiation (No ozone layer), Electrical Activity
  • Atmosphere composed primarily of Nitrogen Gas, Carbon Dioxide, Water vapor, and Hydrogen. No free oxygen Gas.

Origin of Life Hypotheses

Haldane Hypothesis

Early atmosphere composed of methane, ammonia, hydrogen, and water vapor. Energy from radioactivity, lightning, and cosmic rays caused these gases to react, forming organic molecules. These organic molecules then accumulated in oceans, forming a primordial soup. Life further evolved by random chemical reactions and transformations in this complex soup. Heterotrophs would have evolved first.

Steps to the Evolution of Life

  • Requires a large supply of organic molecules produced by non-biological processes.
  • Some process had to assemble those small molecules into complex polymers such as nucleic acids and proteins.
  • Other processes had to organize the polymers into a self-replicating system.

Miller-Urey Experiment

Stanley Miller and Harold Urey designed an apparatus which held a mix of gases similar to those found in Earth’s early atmosphere over a pool of water, representing Earth’s early ocean. Electrodes delivered an electric current, simulating lightning, into the gas-filled chamber. After allowing the experiment to run for one week, they analyzed the contents of the liquid pool. They found that several organic amino acids had formed spontaneously from inorganic raw materials.

Hardy-Weinberg Assumptions

  • Diploid organisms
  • Only sexual reproduction occurs
  • Generations are non-overlapping
  • Mating is random
  • Population size is infinitely large
  • Allele frequencies are equal in the sexes
  • There is no migration, mutation, or selection

RNA World Hypothesis

RNA serves as both template and catalyst for replication. This has been partially reproduced in the lab, but no RNA molecule has been found that can completely self-replicate.

Primate Evolution

Fossil evidence suggests a split in Order Primates about 55 million years ago. At that point, Monkeys, Apes, and Humans diverged from other primates (Prosimians – Lemur, Loris, Galago).

General Characteristics of Primates

  • Opposable Thumbs (and toes – sometimes)
  • Fingernails rather than claws
  • Highly flexible/mobile shoulder and hip joints
  • Binocular Vision
  • Color Vision
  • Language/Communication
  • Usually one offspring at a time