DNA, Flu Viruses, and Genetic Code

• Chapter 10 discusses the structure and function of DNA, including its replication, information flow from DNA to RNA to protein, and the nature of viruses and other noncellular infectious agents.

Why Molecular Biology Matters

• A single DNA "typo" can cause life-threatening diseases.
• All life shares a genetic code.
• DNA can genetically modify organisms like monkeys.
• Enzymes maintain DNA integrity with very high accuracy (greater than 99.999%).
• Mad cow disease is caused by an abnormal protein molecule.

The First 21st-Century Pandemic

• In 2009, a new flu virus, H1N1, spread from Mexico City to California and Texas.
• H1N1 was originally misnamed "swine flu".
• The WHO declared H1N1 the first 21st-century influenza pandemic in June 2009.
• H1N1 was a hybrid flu strain (a combination of viruses from birds, swine, people, and an Asian swine flu virus).
• H1N1 notably affected young and healthy individuals.
• Vaccination efforts contained the virus, and the WHO declared the pandemic over in August 2010.
• The virus killed about 18,000 people, with an estimated 250,000 unreported deaths.
• The influenza virus may be the deadliest pathogen known to science.
• Flu pandemics can cause widespread death.
• The 1918-1919 pandemic killed 40 million people.
• Viruses consist of nucleic acid (RNA in the case of the flu) and protein.
• Combating viruses necessitates understanding life at the molecular level.

DNA: Structure and Replication

• DNA's role in heredity wasn't understood until the late 1930s.
• By the early 1950s, it was accepted that DNA was the hereditary material.
• Molecular biology studies heredity at the molecular level.
• Scientists knew the atoms and bonds in DNA, but not its 3D arrangement.
• DNA's three-dimensional arrangement gives it the capacity to store and copy genetic information.

DNA and RNA Structure

• DNA and RNA are nucleic acids comprised of nucleotide monomers.
• Polynucleotides can be very long with varied sequences.
• Nucleotides are linked by covalent bonds, forming a sugar-phosphate backbone.
• Nitrogenous bases project from the backbone like ribs.
• DNA contains two polynucleotides.
• Nucleotides consist of a nitrogenous base, a sugar (deoxyribose), and a phosphate group.
• Each phosphate has a negative charge.
• The full name for DNA is deoxyribonucleic acid.
• Nitrogenous bases are basic, and differ in DNA nucleotides only by their nitrogenous bases.
• Thymine (T) and cytosine (C) are single-ring structures.
• Adenine (A) and guanine (G) are double-ring structures.
• RNA has uracil (U) instead of thymine.
• RNA contains ribose instead of deoxyribose.
• RNA and DNA polynucleotides share the same chemical structure.

Watson and Crick's Discovery of the Double Helix

• James D. Watson and Francis Crick solved DNA's structure.
• Watson saw Rosalind Franklin's X-ray image of DNA.
• The image indicated DNA's basic shape was a helix with a uniform diameter.
• The helix consisted of two polynucleotide strands, forming a double helix.
• Watson and Crick constructed a model with backbones on the outside and nitrogenous bases swiveled to the molecule interior.
• The four bases pair in a specific way.
• Each base has chemical groups that form hydrogen bonds with a specific partner.
• Adenine (A) pairs with thymine (T).
• Guanine (G) pairs with cytosine (C).
• One DNA strand is a half ladder.
• One may picture the DNA double helix as a full ladder twisted like a spiral.
• There are no restrictions on the nucleotide sequence along a DNA strand.
• Watson and Crick proposed a molecular model for DNA in 1953.
• Few milestones in biology have had as broad of an impact as their double helix model
• Watson, Crick, and Wilkins were awarded the Nobel Prize in 1962 for their work.

DNA Replication

• Every cell contains a complete set of DNA that it must duplicate; which includes providing one copy to new offspring while retaining one copy.
• Each DNA strand serves as a template for reproducing the other strand
• If one polynucleotide sequence is AGTC, then the complementary sequence must be TCAG.
• DNA replication has the two strands of parental DNA separate, and each serves as a template for assembling a complementary strand from free nucleotides
• Each new molecule is identical.
• New molecules become daughter DNA (no gender inferred)
• DNA Replication requires a dozen cooperation of enzymes and other proteins.
• Enzymes called DNA polymerases make covalent bonds between new DNA strand nucleotides.
• DNA polymerase is fast (50 nucleotides per second) and highly accurate
• DNA replication happens a double helix at points called regions of replication.
• DNA replication proceeds in both directions to make replication bubbles.
• Daughter strands elongate both sides of the bubble.
• Replication proceeds simultaneously and shortens time.
• All the bubbles will eventually merge yielding to two double stranded molecules.
• DNA Replication makes all body cells in mutilcellular organisms will carry same organisms.
• DNA Replication means by which genetic information which is passed to offspring.

Information Flow: From DNA to RNA to Protein

• DNA provides a blueprint for an oranganisms as a whole.

How an Organism’s Genotype Determines Its Phenotype

• Organization of an organisms genotype which is heritable information and contained.
• The sequence of nucleotide is in DNA.
• Organisms Physical Traits is called Phenotype.
• Structural proteins make the organisma body.
• Inzymes catalize chemical reactions nessesary for life.
• DNA spesifies the synthesis of proteins.
• DNA is the from of RNA form.
• DNA, Nucueus is sent out as messagers to program protein synthesis.
• Molecules " Chain of Command" is the frome of DNA with with in Nucleus to RNA to protein synthesis in cytoplam.
• Stanges are transcription: Transfer the molecules to formation the trand to amino acid polypeptide(protein strand).
• DNA = dictating to polypeptides.

From Nucleotides to Amino Acids: An Overview

• Genetic information in DNA is transcribed --> RNA and then translated --> polypeptides and folding --> proteins.
• Transcription and Translation are linguistic terms, and it is useful to think of nucleic acids and proteins as having languages.
• Transfer genetic informs to genotype to phenotype.
• Translate Chemical Language of DNA to proteins.
• The Languages of nuecleic acids is made with 4 monomers strung together with codes.
• DNA language is written as a linear sequence
• RNA, the base U is the transcription is RNA molecule

The Genetic Code

• The Genetic code is the code in RNA amino acid sequece.
• 61 triplets codes are with molecules ( as figutre 10/10)
• Triple AUG is the has the amino acid methionine (Met) and start polypeptieds.
• 3 cordons are with not molecules UAA, UAG, and UGA ( ribosomes stop.
• RNA triplet codes for amino always.
• The molecucles is with Linear DNA
• Molecules are for the bacteria to plants. universality sugest that evolution and live today.

Explore DNA's function, the 2009 H1N1 flu virus uniqueness, and DNA structure. Understand nucleic acids, polymers, nucleotides, and DNA strands arrangement. Learn about the universality of the genetic code, the role of enzymes, and DNA replication importance.