DNA Structure and Functions

Structure of DNA

• Double helix model: two complementary strands twisted together
• Each strand composed of nucleotides, which are the building blocks of DNA
• Nucleotides consist of:
  • Sugar molecule (deoxyribose)
  • Phosphate group
  • Nitrogenous base (A, C, G, or T)

Nitrogenous Bases

• Adenine (A) pairs with Thymine (T)
• Guanine (G) pairs with Cytosine (C)
• Base pairing is complementary and specific

Functions of DNA

• Storage of genetic information
• Inheritance of traits
• Cell division and replication
• Mutation and evolution

DNA Replication

• Semi-conservative model: each new DNA molecule contains 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

DNA Transcription

• Synthesis of RNA from DNA template
• Transcription factors bind to specific DNA sequences to initiate transcription
• RNA polymerase reads the DNA template and adds nucleotides to the growing RNA chain
• Resulting RNA molecule is complementary to the DNA template

DNA Mutation

• Changes in the DNA sequence
• Types of mutations:
  • Point mutations: single nucleotide change
  • Frameshift mutations: insertion or deletion of nucleotides
  • Chromosomal mutations: changes in the number or structure of chromosomes
• Consequences of mutations:
  • Silent mutations: no effect on protein function
  • Missense mutations: altered protein function
  • Nonsense mutations: premature termination of protein synthesis

Structure of DNA

• Double helix model consists of two complementary strands twisted together
• Each strand is composed of nucleotides, the building blocks of DNA
• Nucleotides are made up of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base (A, C, G, or T)

Nitrogenous Bases

• Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C) through complementary and specific base pairing

Functions of DNA

• DNA stores genetic information
• DNA is responsible for the inheritance of traits
• DNA plays a crucial role in cell division and replication
• DNA mutations drive evolution

DNA Replication

• Semi-conservative model ensures each new DNA molecule contains one old strand and one new strand
• Helicase unwinds the double helix during DNA replication
• Primase adds RNA primers to the template strands to initiate replication
• DNA polymerase synthesizes new strands by adding nucleotides
• Ligase seals the gaps between nucleotides to complete DNA replication

DNA Transcription

• Transcription involves the synthesis of RNA from a DNA template
• Transcription factors bind to specific DNA sequences to initiate transcription
• RNA polymerase reads the DNA template and adds nucleotides to the growing RNA chain
• The resulting RNA molecule is complementary to the DNA template

DNA Mutation

• Mutations involve changes in the DNA sequence
• Types of mutations include point mutations, frameshift mutations, and chromosomal mutations
• Consequences of mutations include silent mutations, missense mutations, and nonsense mutations
• Silent mutations have no effect on protein function, while missense mutations alter protein function and nonsense mutations prematurely terminate protein synthesis