DNA Function, Genes, and Cell Division

DNA Functions and Information Storage

• DNA stores information to build everything in our bodies.

  • DNA's primary function is to store genetic information which determines the characteristics of an organism.

• Genes, located within DNA, encode instructions for building macromolecules.

  • Genes provide the blueprint for creating proteins and other essential molecules.

• Essential for cell division to duplicate DNA.

  • Accurate DNA duplication ensures that each new cell receives the correct genetic information.

• Important for repair and maintenance in adults.

  • DNA contains the instructions for repairing damaged tissues, maintaining overall health.

• Cells consistently make new copies, necessitating copying genetic information to build cell components.

  • This copying process, known as replication, allows cells to create duplicate copies of DNA for new cells.

Nucleic Acids: DNA and RNA

• Nucleic acids are a type of macromolecule.

  • Nucleic acids, including DNA and RNA are large biomolecules essential for all known forms of life.

• Focus primarily on DNA; also discuss RNA.

  • While DNA holds the genetic code, RNA plays a crucial role as the messenger molecule.

• Central dogma of biology: DNA → RNA → protein.

  • Information flows from DNA to RNA to protein, a fundamental principle in molecular biology.

• A gene is a DNA segment with instructions for making a biological product (primarily proteins).

  • Genes dictate the traits, functions, and characteristics of an organism.

DNA: The Storage Molecule

• Full name: deoxyribonucleic acid.

  • DNA is a molecule composed of two chains that coil around each other to form a double helix carrying genetic instructions for all known living organisms and many viruses.

• DNA stores massive amounts of information.

  • The information stored in DNA directs cell activities, growth, and development.

• Sequencing a genome requires computers that can process terabytes of data.

  • Analyzing DNA sequences helps scientists understand genetic variations and diseases.

• Lining up DNA molecules from all body cells would stretch to the sun and back 300 times (Sun is 93,000,000 miles away).

  • The sheer length of DNA highlights its capacity to store vast amounts of information.

Polymers and Nucleotides

• Polymers are macromolecules made of many units.

  • Polymers are long chains of repeating units that form larger molecules.

• Monomers in DNA are nucleotides.

  • Nucleotides are the building blocks (monomers) that make up the polymer DNA.

• DNA is a polymer made up of nucleotides.

  • The specific sequence of these nucleotides determines the genetic code.

Nucleotide Structure

• Each nucleotide has three components:

  • Nucleotides are composed of three distinct parts.

  • Phosphate group (phosphorus and oxygen atoms) - similar to ATP.

  • The phosphate group provides structural support and is involved in energy transfer.

  • Five-carbon sugar (deoxyribose).

  • Deoxyribose is a pentose sugar that forms part of the DNA backbone.

  • Nitrogenous base (adenine, thymine, cytosine, or guanine).

  • These bases form the "rungs" of the DNA ladder and carry the genetic code.

Nitrogenous Bases

• Four nitrogenous bases: adenine (A), thymine (T), cytosine (C), guanine (G).

  • These four bases make up the genetic alphabet in DNA.

• Genetic information is written in a four-letter code.

  • The sequence of these bases determines the traits and functions of an organism.

• The sequence of these bases constitutes the genetic code, dictating protein synthesis.

  • The precise order of nitrogenous bases determines the amino acid sequence.

Complementary Base Pairing

• Adenine (A) always pairs with thymine (T).

  • This A-T pairing is essential for maintaining DNA structure.

• Guanine (G) always pairs with cytosine (C).

  • The G-C pairing ensures accurate DNA replication.

• Thymine and adenine form two hydrogen bonds.

  • The two hydrogen bonds between A and T stabilize the DNA structure.

• Cytosine and guanine form three hydrogen bonds.

  • The three hydrogen bonds between C and G provide extra stability which is crucial for proper DNA functioning.

DNA: The Double Helix

• DNA is a double helix, with two strands twisting around each other.

  • The double helix structure resembles a twisted ladder, providing stability and protection.

• Strands are complementary due to base pairing rules.

  • Complementary strands ensure that genetic information is accurately copied during cell division.

• Knowing one strand's sequence allows determination of the other strand.

  • Understanding the sequence of one strand is critical for decoding genetic information.

• Important for DNA replication and RNA transcription.

  • The double helix structure facilitates accurate replication, transcription, and RNA synthesis.

• DNA must be copied/replicated, synthesized prior to cell division to ensure genetic inheritability in daughter cells.

  • Accurate replication ensures that daughter cells receive the correct genetic information.

DNA Replication and Repair

• The complementary base pairing scheme is crucial for DNA replication.

  • This scheme allows for the creation of identical DNA copies during cell division.

• Needed for making new cells, repairing damage to tissues.

  • DNA replication and repair mechanisms are essential for maintaining the health of the organism.

Molecular Structure of DNA

• Sugar-phosphate backbone (ribose sugar and phosphate groups).

  • The backbone provides structural support and maintains the DNA's integrity.

• Each nucleotide contains a phosphate group, sugar, and nitrogenous base.

  • These components are arranged systematically to form a functional DNA molecule.

• Thymine always pairs with adenine; cytosine always pairs with guanine.

  • This base pairing ensures accurate DNA replication and genetic inheritance.

Semiconservative DNA Replication

• Each new DNA strand is created using one old strand as a template.

  • This process ensures that each daughter cell inherits genetic information accurately.

• Original DNA molecule separates into two strands.

  • Separation of the strands is facilitated by enzymes like helicase.

• Cell division requires DNA replication, is different from gene expression.

Process of Semiconservative Replication

• Each old strand of DNA serves as a template for a new strand.

  • The old strand guides the synthesis of a new, complementary strand.

• Two new DNA molecules are produced, each with half old and half new DNA.

Enzymes Involved in DNA Replication

• Helicase unzips the DNA by breaking hydrogen bonds.

  • This unwinding is essential for accessing the genetic information.

• DNA polymerase synthesizes new DNA strands using free nucleotides.

  • DNA polymerase ensures the accurate addition of nucleotides to the new strand.

• DNA Fragments must be fused together

  • Fragments are created on the lagging strand as a result of the way DNA Polymerase works

• DNA ligase fuses newly synthesized fragments into one intact molecule.

  • DNA ligase ensures the integrity of the new DNA molecules by correctly fusing the fragments.

Comparing DNA and RNA

• RNA (ribonucleic acid) is the intermediate between DNA and protein.

  • RNA acts as a messenger carrying genetic information from DNA to ribosomes.

• DNA provides long-term storage while proteins are functional manifestations.

  • DNA stores the genetic code, while proteins carry out various cellular functions.

• DNA is double-stranded, and RNA is single-stranded.

  • This structural difference affects their stability and function.

• DNA is more stable; RNA is less stable.

  • The