Molecular Genetics and DNA/RNA

Molecular Genetics

• Study of heredity and variation through molecular structure, function, and processes of nucleic acids.

DNA Replication

• Mechanism: The process of copying a double-stranded DNA molecule into two identical DNA molecules.
• Key Components:
  • Sugar-phosphate backbones: Form the structural framework of DNA and RNA.
  • Base Pairing:
  • DNA: Adenine (A) pairs with Thymine (T); Cytosine (C) pairs with Guanine (G).
  • RNA: Adenine (A) pairs with Uracil (U); Cytosine (C) pairs with Guanine (G).

Structural Differences Between DNA and RNA

• DNA:

  • Double-stranded
  • Contains Thymine (T)
  • Deoxyribose sugar

• RNA:

  • Single-stranded
  • Contains Uracil (U)
  • Ribose sugar

DNA Structure

• Anti-parallel Configuration:
  • DNA strands run in opposite directions:
  • 5' to 3'
  • 3' to 5'
  • Visual analogy: like one-way streets in opposite directions.
• Nucleotide Composition:
  • Each nucleotide consists of:
  • A phosphate group
  • A five-carbon sugar (deoxyribose in DNA)
  • A nitrogenous base (A, T, C, or G for DNA)

Nucleotide Addition during Replication

• Nucleotides can only be added to the 3' end of a growing chain.
• Directionality Importance:
  • DNA synthesis occurs from the 5' end to the 3' end.
• Leading and Lagging Strands:
  • Leading strand: synthesized continuously.
  • Lagging strand: synthesized in Okazaki fragments.

Transcription Process

• Overview:
  • The process of creating an mRNA copy of a gene from DNA.
• Steps:
  • DNA unwinds and separates.
  • RNA polymerase synthesizes RNA from the template strand of DNA, resulting in a complementary RNA sequence.
  • mRNA is processed and transported from the nucleus to the cytoplasm for translation.

Genetic Central Dogma

• Flow of genetic information:
  • DNA → RNA → Protein
  • The sequence of bases in DNA (A's, C's, G's & T's) determines the sequence of ACGU's in RNA, which then determines the amino acid sequence in proteins.

Practical Applications

• Finding Human Genes:
  • Utilize resources like OMIM.org to study gene functions and their associated phenotypes.
• Terms:
  • Genotype: The specific genetic makeup inherited from parents.
  • Phenotype: The observable traits resulting from the genotype (e.g., skin color, eye color).