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

Learn about the double helix model of DNA, its components, and the pairing of nitrogenous bases. Understand the functions of DNA, including storage of genetic information and inheritance of traits.