Exam Preparation Notes

A.D.H.D. (Attention-Deficit/Hyperactivity Disorder) Overview

• Prevalence: Over 7 million U.S. children diagnosed; significant portion (23%) are 17-year-old boys.

• Diagnostic Complexity: Understanding of A.D.H.D. is less clear today than before; reliance on genetic or brain-based biomarkers has largely not yielded results.

• Symptoms: Varied and overlap with conditions like anxiety, trauma, and autism; only 1 in 9 show consistent symptoms throughout childhood.

• Temporary vs. Lifelong: Some researchers argue it may be a temporary condition rather than a lifelong disorder.

• Medication Shortcomings:

  • Drugs like Ritalin improve symptoms in the short term (within 36 months).

  • Medication may enhance focus but does not guarantee better academic performance.

  • Affect motivation by making tasks more engaging rather than enhancing intelligence.

• Environmental Influence: Children's behavior improves in supportive, engaging environments.

• Evolving Perspective: Shift from a strictly medical model to one considering ADHD as a mismatch between a child's brain and their environment.

The Science of Translation in Biology

Components of Translation

• Nucleus: Site of DNA.

• Cytoplasm: Where translation occurs.

• mRNA (messenger RNA): Carries genetic information from DNA.

• tRNA (transfer RNA): Brings amino acids to the ribosome.

• Ribosome: Site of protein synthesis that translates mRNA into a polypeptide chain.

The Elongation Cycle of Translation

1. Codon Recognition: tRNA pairs with the corresponding mRNA codon.

2. Peptide Bond Formation: Amino acids on adjacent tRNAs form a peptide bond.

3. Translocation: Ribosome moves the tRNA from the A site to the P site, advancing the mRNA in the ribosome.

Termination of Translation

• Release Factor: Binds to the stop codon on mRNA, facilitating hydrolysis between last amino acid and tRNA.

• Post-Termination: Disassembly of ribosomal subunits and degradation of mRNA to be recycled.

• Stop Codons: UAG, UAA, and UGA are three stop codons used in translation.

The Wobble Hypothesis

• Total of 64 mRNA codons but only 61 coding (3 are stop codons).

• There are about 40 tRNA molecules for codon recognition.

• Wobble base pairing: Some tRNAs can pair with multiple codons due to flexibility in the third base of the codon, following specific rules.

Protein Folding and Modifications

• Protein Structure Levels:

  • Primary Structure: Linear chain of amino acids (e.g. A1, A2)

  • Secondary Structure: Formation of shapes like alpha-helices or pleated sheets.

  • Tertiary Structure: Overall 3D structure of a single protein (e.g. Hemoglobin).

  • Quaternary Structure: Association of multiple protein subunits.

• Post-Translational Modifications:

  • Phosphorylation: Common modification that regulates protein activity.

  • Glycosylation: Tags proteins to promote folding and stability.

  • Methylation: Affects transcription regulation, RNA processing, and other cellular processes.