Molecular Biology: DNA Structure and Replication

DNA Structure and Replication

• DNA (Deoxyribonucleic acid) is a double-stranded helix composed of nucleotides
• Each nucleotide consists of:
  • Sugar molecule (deoxyribose)
  • Phosphate group
  • Nitrogenous base (A, C, G, or T)
• Hydrogen bonds between nitrogenous bases hold the two strands together
• Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C)

Central Dogma

• DNA is transcribed into RNA (ribonucleic acid)
• RNA is translated into proteins
• Proteins perform various cellular functions
• Genetic information flows from DNA to RNA to proteins

DNA Replication

• Semi-conservative replication: each new DNA molecule consists of one old strand and one new strand
• Steps:
  1. Helicase unwinds the double helix
  2. Primase adds RNA primers to the template strands
  3. DNA polymerase synthesizes new strands
  4. Ligase seals the gaps between nucleotides

Gene Expression

• Gene expression is the process by which genetic information is converted into a functional product
• Steps:
  1. Transcription: DNA is transcribed into RNA
  2. Translation: RNA is translated into a protein
  3. Post-translational modification: protein is modified to become functional

Mutations

• A change in the DNA sequence
• Types:
  • Point mutations: substitution of one nucleotide for another
  • Frameshift mutations: insertion or deletion of nucleotides
  • Chromosomal mutations: changes in the number or structure of chromosomes

Inheritance Patterns

• Mendel's laws:
  • The law of segregation: each pair of alleles separates during gamete formation
  • The law of independent assortment: alleles for different genes are sorted independently
  • The law of dominance: one allele can be dominant over another
• Autosomal dominant/recessive inheritance
• X-linked inheritance
• Polygenic inheritance

DNA Structure

• DNA is a double-stranded helix composed of nucleotides, each consisting of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base (A, C, G, or T)
• Hydrogen bonds between nitrogenous bases hold the two strands together
• Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C)

Central Dogma

• DNA is transcribed into RNA (ribonucleic acid)
• RNA is translated into proteins
• Proteins perform various cellular functions
• Genetic information flows from DNA to RNA to proteins

DNA Replication

• Semi-conservative replication: each new DNA molecule consists of one old strand and one new strand
• Helicase unwinds the double helix
• Primase adds RNA primers to the template strands
• DNA polymerase synthesizes new strands
• Ligase seals the gaps between nucleotides

Gene Expression

• Gene expression is the process by which genetic information is converted into a functional product
• Transcription: DNA is transcribed into RNA
• Translation: RNA is translated into a protein
• Post-translational modification: protein is modified to become functional

Mutations

• A change in the DNA sequence
• Point mutations: substitution of one nucleotide for another
• Frameshift mutations: insertion or deletion of nucleotides
• Chromosomal mutations: changes in the number or structure of chromosomes

Inheritance Patterns

• Mendel's laws:
  • The law of segregation: each pair of alleles separates during gamete formation
  • The law of independent assortment: alleles for different genes are sorted independently
  • The law of dominance: one allele can be dominant over another
• Autosomal dominant/recessive inheritance
• X-linked inheritance
• Polygenic inheritance

This quiz covers the structure and replication of DNA, including its double-stranded helix composition and the process of transcription and translation.