In-Depth Notes on DNA and RNA Structure, Function, and Processes

Key Concepts about DNA and RNA

• DNA and Traits

  • DNA contains instructions that determine traits, such as blood types (e.g., Type A contains specific genes that instruct the cell to produce certain proteins).
  • Proteins play a vital role in various biological functions.

• Genes and Proteins

  • Each gene is a segment of DNA that contains instructions for making a protein.
  • The concept of "one gene, one protein" indicates that most genes code for proteins, with few exceptions where a gene may encode for non-protein molecules.

Genetic Instructions and Blood Types

• Example of Blood Types
  • People with Type A blood carry at least one allele that codes for glycoprotein A on red blood cells.
  • Those with Type B blood have a different gene, coding for glycoprotein B.
  • Hemophilia Case Study
  • Hemophiliacs have faulty instructions preventing the production of a clotting protein, leading to blood clotting issues.

Structure of DNA

• Basic Components of DNA

  • DNA (Deoxyribonucleic Acid) is a nucleic acid made of smaller units called nucleotides.
  • Each nucleotide consists of three components:
  1. Pentose Sugar (5-carbon sugar): Deoxyribose in DNA.
  2. Phosphate Group: Essential for forming the DNA structure.
  3. Nitrogenous Bases: Four types exist - Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

• Structures of Nitrogen Bases

  • Nitrogen bases are categorized into:
  • Purines: (A, G) - Two-ring structures.
  • Pyrimidines: (C, T) - One-ring structures.

Sugar-Phosphate Backbone and Base Pairing

• Sugar-Phosphate Backbone

  • Linkages of the sugar of one nucleotide to the phosphate group of another form a backbone.

• Base Pairing

  • A pairs with T via two hydrogen bonds, while C pairs with G via three hydrogen bonds.
  • This complementary base pairing is crucial during DNA replication and transcription.

Double Helix Structure

• DNA Structure
  • DNA forms a double helix, where two strands twist around each other, held together by hydrogen bonds between complementary nitrogenous bases.
  • The two strands are antiparallel, meaning they run in opposite directions (5' to 3' and 3' to 5').

DNA Replication Process

• Semi-Conservative Replication

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

• Key Enzymes in Replication

  1. DNA Helicase: Unwinds and separates the two strands of DNA.
  2. DNA Polymerase: Adds new nucleotides complementary to the template strand, synthesizing the new strand.
  3. DNA Ligase: Joins Okazaki fragments on the lagging strand to form a continuous strand.

RNA Structure and Types

• Differences Between RNA and DNA

  • RNA contains ribose (as opposed to deoxyribose in DNA).
  • RNA is typically single-stranded.

• Types of RNA

  • mRNA (Messenger RNA): Carries genetic instructions from DNA to ribosomes for protein synthesis.
  • tRNA (Transfer RNA): Transports amino acids to ribosomes.
  • rRNA (Ribosomal RNA): Forms the core structure of ribosomes.

Transcription and Translation

• Transcription Process

  • DNA sequences are transcribed into mRNA, which carries the information from the nucleus to the cytoplasm.
  • Purpose of Transcription
  • Acts as a copy of the DNA sequence for protein synthesis while safeguarding the DNA.

• Translation Process

  • Involves decoding the mRNA at the ribosomes to synthesize proteins using amino acids.
  • Ribosomes read the mRNA and facilitate the assembly of amino acids into polypeptide chains, creating proteins based on the genetic code.