Unit 10.5 – Nucleic Acids 🧬

1. The Big Picture

Traits travel from parents to children through chromosomes in the nucleus, and those chromosomes contain two star molecules: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Because both are long chains of nucleotides, scientists also call them polynucleotides.:contentReference[oaicite:0]{index=0}

2. Building Blocks

  • Ingredients after complete hydrolysis: a pentose sugar, phosphoric acid, and nitrogen-containing bases.:contentReference[oaicite:1]{index=1}
  • Sugar choice: β-D-2-deoxyribose in DNA and β-D-ribose in RNA.:contentReference[oaicite:2]{index=2}
  • Base roster: DNA uses adenine (A), guanine (G), cytosine (C), and thymine (T); RNA swaps thymine for uracil (U).:contentReference[oaicite:3]{index=3}
  • Nucleoside: base attached to the 1′ carbon of the sugar.:contentReference[oaicite:4]{index=4}
  • Nucleotide: nucleoside plus a phosphate at the 5′ carbon.:contentReference[oaicite:5]{index=5}

3. Linking the Units

Nucleotides join head-to-tail through a 3′→5′ phosphodiester linkage, building an endless sugar-phosphate backbone. A quick sketch in KaTeX shows the bridge:

\( 5′ \text{P}–O–3′ \) :contentReference[oaicite:6]{index=6}

4. Levels of Structure

  • Primary structure: the exact nucleotide sequence along a single chain.:contentReference[oaicite:7]{index=7}
  • Secondary structure of DNA: the famous double helix—two complementary strands twist together like a gentle ladder; A pairs with T and G pairs with C through hydrogen bonds.🪜:contentReference[oaicite:8]{index=8}
  • Secondary structure of RNA: usually single-stranded, but it can fold back on itself. There are three main flavors: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).:contentReference[oaicite:9]{index=9}

5. What They Do 🚀

  • DNA—memory chip of life: stores genetic information, duplicates itself during cell division, and passes perfect instructions to daughter cells.:contentReference[oaicite:10]{index=10}
  • RNA—hands-on worker: reads DNA’s instructions and helps assemble proteins.:contentReference[oaicite:11]{index=11}
  • DNA fingerprinting: the unique base sequence in each person’s DNA is now key in forensics, paternity tests, disaster victim ID, and evolutionary studies.🔍:contentReference[oaicite:12]{index=12}

6. High-Yield NEET Nuggets 🔑

  1. Base swap: DNA has T, RNA has U.
  2. Bond type: 3′-5′ phosphodiester linkage glues the backbone.
  3. Complementary pairing: A↔T (or U in RNA) and G↔C ensure accurate replication.
  4. Three Rs of RNA: mRNA carries the message, rRNA forms ribosomes, tRNA ferries amino acids.
  5. DNA fingerprinting: unique sequences for rock-solid identification.

✨ Keep these pointers handy, and nucleic acids will feel much less daunting! ✨