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DNA Structure and Function

  • DNA Definition: A complex molecule (polymer) found in all living organisms.

  • Primary Function: Stores and transmits genetic information, directing cells on when and how to produce proteins.

  • Polymers: Composed of repeating subunits called nucleotides.

Nucleotides

  • Components of Nucleotides:

    • Sugar:

      • Deoxyribose (in DNA, a 5-carbon sugar)

      • Ribose (in RNA, a 5-carbon sugar with more oxygen than deoxyribose)

    • Nitrogen Bases:

      • Purines (double ring):

        • Adenine (A)

        • Guanine (G)

      • Pyrimidines (single ring):

        • Thymine (T, replaced by Uracil (U) in RNA)

        • Cytosine (C)

    • Phosphate Group: PO4

Base-Pairing Rules

  • Complementary Base Pairs:

    • Cytosine (C) pairs with Guanine (G) - forms three hydrogen bonds.

    • Adenine (A) pairs with Thymine (T) - forms two hydrogen bonds.

DNA Replication and Chromosomes

  • Replication: The process of duplicating the DNA molecule before cell division.

  • Chromosomes: Coiled, double rod-shaped structures of condensed DNA. Formed during cell division.

    • Each chromosome consists of one original DNA strand and one newly synthesized DNA strand.

    • Ensures equal genetic distribution to daughter cells.

    • Human Chromosomes: 46 total (23 pairs).

RNA: Types and Functions

  • RNA Function: Moves genetic information from DNA to the site of protein synthesis in the cytoplasm.

  • RNA Sugar: Ribose (different from DNA's deoxyribose).

Types of RNA

  • Messenger RNA (mRNA):

    • A single uncoiled strand that transmits information from DNA to ribosomes for protein synthesis.

  • Transfer RNA (tRNA):

    • A single folded strand that binds to specific amino acids.

  • Ribosomal RNA (rRNA):

    • Major component of ribosomes.

Processes of Protein Synthesis

Transcription

  • Definition: Process of forming an mRNA strand from a DNA strand.

    • The DNA double strands separate, and mRNA is formed by base pairing with exposed DNA sequences.

    • Rate of Transcription: Approximately 40 nucleotides per second.

Translation

  • Definition: Assembling protein molecules using the information coded in mRNA.

Central Points to Note

  • DNA Replication: DNA duplicates itself.

  • Transcription: DNA produces RNA.

  • Translation: RNA produces proteins.