DNA Function, H1N1 Virus, DNA Replication Accuracy

• Molecular biology studies heredity at the molecular level
• Understanding the structure and function of DNA is critical in molecular biology

DNA Structure and Replication

• By the late 1930s, biologists were convinced inheritance had a molecular basis
• Attention shifted to chromosomes known to carry genes
• Scientists discovered chromosomes consist of DNA and protein by the 1940s
• By the early 1950s, DNA identified as hereditary molecule, leading to molecular biology
• Molecular biology is the study of heredity at the molecular level
• The understanding of DNA's three-dimensional arrangement that gives it the ability to store genetic information, copy it, and pass it from generation to generation, was one of the most celebrated quests in science

DNA and RNA Structure

• Both are nucleic acids
• Consist of polymers of nucleotide monomers
• Polynucleotides can be very long and may have variety of sequences
• Nucleotides are joined by covalent bonds between the sugar of one and the phosphate of the next
• Backbone: Repeating pattern of sugar-phosphate-sugar-phosphate
• Nitrogenous bases project from the backbone
• A polynucleotide is like a long ladder split in half
• Sugars and phosphates are sides, sugars acting as half-rungs
• Nucleotides consist of a nitrogenous base, a sugar, and a phosphate group
• The phosphate group (phosphorus atom at center) is the source of acid in nucleic acid
• Phosphates have a negative charge on one of their oxygen atoms
• Sugar has five carbon atoms and includes an oxygen atom
• Sugar is deoxyribose, missing an oxygen atom compared to ribose
• DNA's full name is deoxyribonucleic acid
• Nucleic refers to DNA's location in the nuclei of eukaryotic cells
• The nitrogenous base has a ring of nitrogen and carbon atoms with chemical groups attached
• Nitrogenous bases are basic (high pH)
• Four nucleotides in DNA differ only in nitrogenous bases
• Thymine (T) and cytosine (C) are single-ring structure
• Adenine (A) and guanine (G) are larger, double-ring structures
• RNA has uracil (U) instead of thymine
• RNA contains a slightly different sugar than DNA, ribose instead of deoxyribose
• RNA and DNA polynucleotides have same chemical structure

Watson and Crick's Discovery of the Double Helix

• American James D. Watson and Francis Crick solved the puzzle of DNA structure
• Watson saw Rosalind Franklin's X-ray image of DNA, which identified that the basic shape of DNA is a helix with a uniform diameter
• Franklin's data key to the puzzle
• Thickness of the helix suggested two polynucleotide strands, a double helix
• Watson and Crick built wire models to conform to data
• Placed backbones on outside, nitrogenous bases swiveled to molecule's interior
• The four kinds of bases must pair in a specific way
• Each base has chemical groups that best form hydrogen bonds with only one partner
• Adenine pairs with thymine, guanine with cytosine with hydrogen bonds
• One strand must always be paired with a single-ringed base on the opposite strand
• the biologist's shorthand: A pairs with T, and G pairs with C
• A is complementary to T, and G is to C
• A polynucleotide half-ladder picture can be used to see the DNA double helix proposed by Watson and Crick, a full ladder twisted into a spiral
• Although base-pairing rules dictate side-by-side combinations, they place no restrictions on the sequence along DNA strand
• The sequence of bases can vary in countless wa
• In 1953, Watson and Crick proposed DNA model

DNA Replication

• A cell reproduces, duplicates the DNA in a single copy
• Each cell has means for copying DNA instructions
• Watson and Crick's model of DNA suggests each DNA strand is a template to guide reproduction of other strand
• Sequence of bases in one strand helps determine the other strand
• Base-pairing rules dictates that A pairs with T to form the sequence AGTC, then the complementary polynucleotide would have the sequence TCAG
• Model accounts for direct copying of a piece of DNA
• Strands of parental DNA separate, become templates for the assembly of a complementary strand from free nucleotides in the process of DNA replication
• Nucleotides line up one at a time along a template strand to base-pairing rules
• Enzymes link the nucleotides to form new DNA strands
• Completed new molecules identical to parental molecules
• Daughter DNA molecules are molecules produced from parental DNA molecules
• DNA replication requires enzymes and other proteins
• The enzymes that make covalent bonds between nucleotides of a new DNA strand are called DNA polymerases
• As a nucleotide base-pairs with complement, DNA polymerase adds it to the end of the daughter strand
• Process is fast and accurate; a rate of 50 nucleotides per second is typical, and is accurate to about 99.999%
• DNA, damaged by toxic chemicals or high-energy radiation, may be repaired by DNA polymerase and other associate proteins
• DNA replication begins at origins of replication on the double helix
• Replication proceeds in both directions, creating replication bubbles
• DNA molecule of a eukaryotic chromosome has many origins to start replication simultaneously
• Bubbles merge, yielding two completed double-stranded daughter DNA molecules
• DNA replication ensures all body cells in a multicellular organism carry the same genetic information
• DNA replication passes genetic info to offspring

Information Flow in Living Organisms

• DNA provides instructions to a cell and to an organism as a whole
• An organism's genotype (genetic makeup) contained in the sequence of nucleotide bases in DNA
• Phenotype is the organism's physical traits from actions of variety of proteins like structural proteins and enzymes
• DNA specifies synthesis of proteins
• DNA dispatches instructions in the form of RNA
• Molecular "chain of command" is from DNA in the nucleus to RNA to protein synthesis in cytoplasm
• Stages are transcription, the transfer of genetic information from DNA to RNA molecule, and translation, the transfer of information from RNA into polypeptide
• DNA gene produces a polypeptide

From Nucleotides to Amino Acids

• Genetic information from DNA is transcribed into RNA and then translated polypeptide
• Nucleic acids and proteins are the languages to understand how genetic information passes from genotype to phenotype
• DNA and RNA are polymers
• Polymers are sequences of nucleotide monomers strung together in a language,much like words for letters
• DNA includes four types of nucleotides, which differ in nitrogenous bases (A, T, C, and G), and the same for RNA although it has a base U not T
• The language of DNA is written as a linear sequence of nucleotide bases
• Every gene is a sequence of bases, and has sequences marking the beginning and end
• Gene a few thousand nucleotides long
• Segment of DNA is transcribed, resulting in an RNA molecule
• Nucleic acid language of DNA has been rewritten as the sequence of bases of RNA
• The nucleotide bases of RNA molecule are complementary those of DNA strand and because RNA synthesized using the DNA as a template
• Translation: Convert nucleic acid language to the polypeptide one
• Polypeptides and nucleic acids are polymers, but the monomers in polypeptides are the 20 amino acids shared by all organisms
• The sequence of nucleotides of the RNA molecule dictates the sequence of amino acids of the polypeptide
• RNA is messenger and the genetic originates in DNA
• Rules for translating RNA message into polypeptide: Correspondence Nucleotides
• RNA molecule and amino acids of a polypeptide
• Only four kinds of nucleotides exist in DNA (A, G, C, T) and RNA (A, G, C, U), meaning that in translation the four somehow must specify 20 amino acids
• If each nucleotide base coded for one amino acid, only coded 4 of the 20 amino acids
• Triplets of bases are more likely to coded the amino acids, which can specify all amino acids
• Can be 64 possible code ways of type, so the triplets make up the smallest words of uniform length that can specify all the amino acids
• Experiments verify the flow of information from gene to protein based on a triplet code
• Instructions for amino acid sequence of a polypeptide chain are written in DNA and RNA through a series of three-base and words called codons
• DNA codons transcribed into complementary RNA codons
• RNA codons translated into amino acids forming polypeptide
• One DNA codon is the same as RNA codon to the amino acid

The Genetic Code

• Converts a nucleotide sequence in RNA to an amino acid sequence through the set of rules known as the genetic code
• Codes for amino acids with has a dual function, 61 out of the 64 triplets that code for amino acids also provide a signal or function to the start of polypeptide chain using the triplet AUG with the amino acid methionine (Met)
• Three codons known as codons with (UAA, UGA, and UAG) that do not designate any amino acids are stop codons that instruct ribosomes to end polypeptides
• Given a sequence of RNA, the triplet specifics a given amino acid like examples include codons UUU and UUC
• The codons are triplets found in RNA and a straightforward and complementing version of codons from DNA but make up codons in linear order along DNA and RNA, separated gaps
• Genetic code nearly shared in organisms from the simpler bacteria to more complex animals and plants suggesting the genetic rose earlier and passes down to the all the organism to live
• DNA is universal to life, its possbile to use the versatility and program any specices to create and process proteins of another creating the code
• Reminds people how the kinship to life is created in DNA

Transcription: From DNA to RNA

• Transcription is a transfer tool where RNA gains important and correct information from DNA
• DNA has similar qualities of a cookbook of transcription but the process is transcribed as a recipe
• 10. 12 is a close-up view of the process with replication, the separated DNA becomes a template for the RNA molecules
• Nucleotide base-pairing rules for RNA contains RNA that are linked by the transcription system DNA polymerase and RNA polymerase
• 10.12 overview of the the transcription of the entire DNA where special sequences tell DNA polymerase to stop or start the transcription
• Initiation is located in the promoter that is in the DNA at the end of the gene and the promoter will the determine if start
• Elongation is phase where Rna grows longer while RNA synthesis continues to peel away from DNA, becoming the region is already transcribed
• Termination is when RNA polymerase and the base reaches terminator that can the signal to know when the gene has to stop
• Other types of RNA, in addition, are produce, they help building polpeptides

The Processing of Eukaryotic

• The prokaryotes are cells and lack nuclei while RNA that is transcribed from a gene can immediatly messenger known as RNA that is translated to proteins
• Can occur in eukaryotic cells where processing of the transcripts occurs, but also transcript in modified the nucleis where transcription can proceed.
• Other transcript modification occurs from the addition addition, which it is the attack of the cellular enzymes help ribosomes help know the RNA IS MRNA
• Rna processing occurs in the eurkaroytes from stretches the interrupt where the nucleotide can not the actual cause of a disease
• As a result, coding internal regions can be in known internal while both exons and introns can be in trancrpitted from the MRNA which splicing to signficant role to perform signfifatnly to produce more of a protein

Translation : The Players

• Disccussed during the translation to know the proteins will transfer from the translation
• Rna helps translation begin correctly and helps the messeger in the Rna
• Trnaslation has an other part in celluar to know the amino aids will join during the translation, and carry out the translation in the polyeptide

Translation: The Process

• Process consists of initatition and elongation of the TRNAS during the proccess and the first phase brings the MRAN is atatacted trna atched trna unit
• Initatiation occurs to known exaclty where transation and codes are amino acids in the MRNA
• ertain trna also known atatached to rna moel and is the process is going to begind in a functional ribosome and initator fits the into the site where the protein is at
• Elongation with first ainos added into the proteins with the mrna , can cause the amino acids and the mrans to work together as to site the proteins in the body, but the MRNa are only move
• termination occurs where is does code for amino acids while is to a stop and can cause the protein to break.

From DNA to RNA to Protein

• Transciption occurs in the nucleus, and the RNA is processed before it enters the cytoplasm
• a single ribosome can make an average-sized polypeptide in less than a minute
• It is the overall processes of significance is to control the DNA and RNA of cells
• In turn, the information within the mRNA specifies the sequence of amino acids in a polypeptide
• The proteins cause determine the appearance and capabilities of the cell and organism

Mutations are Hereditable Differences

• Since discovering how genes can translate info code for proteins to describe heritable differnces can be coded
• Sickle cells known as anemia in the heoglobin and differe form the proteins on a coding from polpeptide
• If changes occur within a cells can be called known the Mutaion which causes single paring , improves the functions can change and can have negative out comes
• Occur when known as subsitution or insertion or deletion during the Rna process, if rnan goes with and effects
• Code is random when there and some does change or effect and other that can still transaltes and mean still the same

Mutagens cause Mutation

• Ways that cause errors during recombiant and and spontatenious mutations.
• Physcial muatatiors effect the rna and dna
• chemicals can do the same and some are can cause the agens some lifestyles effect the body to preucation

Plant Viruses and Viruses

• Plant viruses do effect growth and diminsh crop yield as most are RNA
• Affect related plant life

Animal Viruses that Effect the Body

• Most common as decease is caused and affects many can cause damage to tissue and nerves to function that well to produce and fight off to viruses
• Hiv aids known as retroviruses
• Hiv is retrovirus because can damage rna or dan reverse the effects so to slow or stop the infections

Viroids and Prions

• Viruses that infect plants cells can stunt plant growth and diminish corp yields as most are known
• Plant cells can regulate the cause diseases through interference cells

Emerging Viruses

• Emergin gviruses may affect humans and have the mutation of viruses
• Can be cause by the mutations for the cause has new strains for people
• Originated in animals and species which some spread diseases to un treated and not heard known cells

Explore the primary function of DNA in living organisms. Learn about the hybrid nature of the 2009 H1N1 flu virus strain and its origins. Understand why accurate DNA replication and maintenance are critical for life.