Heredity

Lab & Course Logistics

• End of lab sessions: No labs after today.
• Remaining assessments:
  • One final lab quiz next Tuesday covering heredity (today’s material).
  • Final exam on Thursday.
  • Optional extra-credit assignment due before semester ends (ideal to finish before the final for practice).
• Tuesday plan (non-lab day):
  • Review session for final.
  • Opportunity to see and discuss dissected pregnant rat specimen.
  • Time to clarify confusing heredity concepts from today.
• Printed review sheets available (courtesy of Dr. O’Connell); hard copy recommended over online version.

Central Dogma Refresher (A&P I Review)

• DNA (long-term storage) → mRNA (short-lived copy) → Protein (functional output).
• Genes = discrete DNA regions containing instructions for proteins.
• mRNA is transcribed from genes, then translated into proteins.
• Protein importance examples: eye color pigment enzymes, hair keratins, sodium-potassium pump, proton pump, antibodies, collagen, actin, myosin, neuronal ion channels.
• Take-home: Every cellular structure/function ultimately traces back to proteins coded by DNA.

“Recipe Book” Metaphor for Genomes

• DNA ≈ a giant cookbook; each gene ≈ a recipe.
• Every somatic cell owns the entire cookbook (genes for kidney proteins, neuron proteins, liver proteins, etc.).
• Variation among individuals:
  • Everyone bakes “cookies,” but specific recipes differ slightly (mutation, familial variation).
  • Example: You tweak butter ratio; analogous to an allele difference.
• Critical proteins (e.g., $\text{sodium}\text{-}\text{potassium pump}$) evolve fewer recipe changes; less crucial traits (eye color pigment) tolerate more variability.

Chromosome Structure & Pairing

• Humans: $23$ distinct chromosomes per haploid set; diploid somatic cells hold $23 \text{ pairs}$ (total $46$).
• Chromosomes numbered by length: $1$ (longest) → $23$ (shortest).
• You inherit one copy of each chromosome from mother, **one