Genetics Chapter: DNA Structure and Replication

Genetics

DNA Structure

• Double helix model: two complementary strands twisted together
• Each strand composed of nucleotides (A, C, G, and T)
• Sugar-phosphate backbone provides structural support
• Nitrogenous bases (A, C, G, and T) project inward from backbone

DNA Replication

• Semi-conservative model: each new DNA molecule contains one old strand and one new strand
• Process occurs during S phase of cell cycle
• Initiated by helicase enzyme unwinding DNA double helix
• Leading strand synthesized continuously in 5' to 3' direction
• Lagging strand synthesized in short, discontinuous segments (Okazaki fragments) in 5' to 3' direction

Gene Expression

• Central dogma: DNA → RNA → Protein
• Transcription: DNA sequence copied into RNA molecule
• Translation: RNA sequence translated into amino acid sequence
• Gene regulation: mechanisms to control gene expression, including transcription factors and epigenetic modifications

Mendelian Genetics

• Laws of inheritance: segregation, independent assortment, and dominance
• Genotype: genetic makeup of an individual (e.g., BB or Bb)
• Phenotype: physical expression of genotype (e.g., blue eyes or brown eyes)
• Punnett squares: diagrams to predict genotypic and phenotypic probabilities of offspring

Molecular Genetics

• Mutation: change in DNA sequence
• Types of mutations: point, frameshift, and chromosomal
• Genetic code: sequence of nucleotides that determines amino acid sequence
• Recombinant DNA technology: manipulation of DNA sequences in vitro

Genetic Variation

• Sources of variation: mutation, genetic recombination, and gene flow
• Types of genetic variation: allelic, genotypic, and phenotypic
• Hardy-Weinberg equilibrium: mathematical model to describe genetic variation in populations

Epigenetics

• Epigenetic modifications: chemical changes to DNA or histone proteins that affect gene expression
• Types of epigenetic modifications: DNA methylation, histone modification, and chromatin remodeling
• Epigenetic inheritance: transmission of epigenetic modifications from parent to offspring

DNA Structure

• Double helix model consists of two complementary strands twisted together
• Each strand is composed of nucleotides (A, C, G, and T)
• Sugar-phosphate backbone provides structural support for DNA
• Nitrogenous bases (A, C, G, and T) project inward from the backbone

DNA Replication

• Semi-conservative model: each new DNA molecule contains one old strand and one new strand
• DNA replication occurs during S phase of the cell cycle
• Helicase enzyme unwinds the DNA double helix to initiate replication
• Leading strand is synthesized continuously in 5' to 3' direction
• Lagging strand is synthesized in short, discontinuous segments (Okazaki fragments) in 5' to 3' direction

Gene Expression

• Central dogma: DNA sequence is copied into RNA molecule, then into amino acid sequence
• Transcription: DNA sequence is copied into RNA molecule
• Translation: RNA sequence is translated into amino acid sequence
• Gene regulation: mechanisms to control gene expression, including transcription factors and epigenetic modifications

Mendelian Genetics

• Laws of inheritance: segregation, independent assortment, and dominance
• Genotype: genetic makeup of an individual (e.g., BB or Bb)
• Phenotype: physical expression of genotype (e.g., blue eyes or brown eyes)
• Punnett squares: diagrams to predict genotypic and phenotypic probabilities of offspring

Molecular Genetics

• Mutation: change in DNA sequence
• Types of mutations: point, frameshift, and chromosomal
• Genetic code: sequence of nucleotides that determines amino acid sequence
• Recombinant DNA technology: manipulation of DNA sequences in vitro

Genetic Variation

• Sources of variation: mutation, genetic recombination, and gene flow
• Types of genetic variation: allelic, genotypic, and phenotypic
• Hardy-Weinberg equilibrium: mathematical model to describe genetic variation in populations

Epigenetics

• Epigenetic modifications: chemical changes to DNA or histone proteins that affect gene expression
• Types of epigenetic modifications: DNA methylation, histone modification, and chromatin remodeling
• Epigenetic inheritance: transmission of epigenetic modifications from parent to offspring