Genetics Chapter: DNA Structure and Replication

Genes and DNA Composition

• Genes are composed of DNA, which carries genetic information.
• DNA is made up of nucleotides, the building blocks of genetic material.

Nucleotide Structure

• Each nucleotide consists of three components: sugar, phosphate group, and a nitrogenous base.

DNA Structure

• Two strands of DNA are held together by hydrogen bonds, forming the double helix structure.
• Nucleotides within a single strand are linked by covalent bonds, creating a stable backbone.

DNA Replication

• DNA replication involves three main steps:
  • Proteins unwind the DNA molecule, causing the strands to separate.
  • DNA polymerase uses the template of the old strands to build new strands.
  • The process results in semi-conservative replication, yielding two DNA double helices, each containing one old and one new strand.

Polymerase Chain Reaction (PCR)

• PCR is a technique used to artificially produce millions of copies of a specific DNA sequence, facilitating genetic analysis.

Mutations

• A mutation refers to any change in the sequence of bases in an organism's DNA.
• Specific types of mutations include:
  • Point mutation: a change in a single base within the sequence.
  • Substitution: a correct base is replaced with an incorrect one, potentially altering gene function.
  • Insertion: one or more bases are added, affecting the reading frame of the genetic code.
  • Deletion: one or more bases are removed, also altering how the sequence is read.