Nucleic Acids (DNA & RNA)

• Composed of C O H N & P to form the nucleotides.

• Nucleotides include: - a 5 carbon sugar - a phosphate group - a nitrogen base ( 5 types)

1. Thymine ( T ) 4. Guanine ( G )2. Adenine ( A ) 5. Uracil ( U )3. Cytosine ( C )

Nucleic Acid con’t

• These nucleotides (monomers) are arranged to form the (polymers) nucleic acids DNA & RNA.

DNA (deoxyribonucleic acid)

• Long double-stranded polymer that is twisted forming a double helix.

• The backbone of the ladder-like molecules are formed by alternating sugar (deoxyribose) & phosphate units.

DNA con,t

• The rungs are formed by the binding together of complementary bases (A- T & G - C) by hydrogen bonds

• DNA is located in the nucleus of a cell.

• Is the genetic material, directs protein synthesis, & replicates itself before cell division

• Chromosomes are structures in the nucleus of a cell that contain genetic (DNA) information that is passed on from one generation to another

DNA the discovery of

• *1865- Gregor Mendel, working alone in Austria, discovers that some characteristics are inherited in ‘units’.

• 1870- Friedrich Miescher isolates chemicals from the cell nucleus, including ‘nucleic acids’.

• 1879-Walter Flemming describes behavior of chromosomes during cell division, implicating these nuclear structures in inheritance.

• 1900- Hugo DeVries and others rediscover Mendel’s work and establish first laws of inheritance.

• *1909- Wilhelm Johannsen coins the term ‘gene’.

The History of DNA continues!!!

• 1910- Thomas Hunt Morgan is the first to show that genes are arranged in a linear fashion along chromosomes.

• 1928- Frederick Griffith uses a chemical extract to convert harmless pneumonia bacteria into pathogenic forms nature of this ‘inheritance factor’, however, is unknown.

• *1929- Phoebus Levene discovers that a sugar, deoxyribose, is present in nucleic acids. Later identifies that DNA is made up of nucleotides, a chemical unit comprising a deoxyribose sugar, a phosphate group and one of four small organic molecules known as nitrogen bases.

Rome wasn’t built in one day

• 1941- George Beadle and Edward Tatum show that genes direct the production of proteins.

• *1943-William Astbury makes the first X-ray diffraction images of DNA.

• 1944- Oswald Avery and colleagues show that DNA can ‘transform’ cells cementing the link between DNA and genes. His team determines that genes are composed of DNA.

• *1950-Edwin Chargaff discovers that there are patterns in the amounts of the four bases in DNA: the amounts of G and C, and of A and T, are always the same.

Still Building Rome !!!!!

• 1951- Linus Pauling and Robert Corey determine that the structure of a class of proteins is a helix.

• 1960 – Sydney Brenner and other scientists show the existence of messenger RNA.

• 1977 – Walter Gilbert, Allan Maxam, and Fredrick Sanger develop methods to read the DNA Sequence.

• 2000 – Human Genome Project an attempt to sequence all human DNA is essentially complete.

The Discovery of DNA continues.

• *1952- Rosalind Franklin and her colleague, Maurice Wilkins takes her first X-ray diffraction pictures, and she writes a paper proposing that DNA is so thick that it is probably doubled.

• *1953- James Watson and Francis Crick publish first paper proposing a double helix structure for DNA. James Watson and Francis Crick

Rosalind Franklin's X-ray diffraction photograph of DNA, 1953

DNA Review• Nucleotides include:

• - a 5 carbon sugar

• - a phosphate group

• - a nitrogen base ( 4 types)

• 1. Thymine ( T ) 3.Guanine (G)

• 2. Adenine ( A ) 4. Cytosine ( C )

• These nucleotides (monomers) are arranged to form the (polymers) nucleic acids DNA & RNA.

• The bases are grouped as purines and pyrimidines

• Purines= Adenine & Guanine

• Pyrimidines= Thymine, Cytosine & Uracil (found only in RNA)

Prokaryote DNA versus Eukaryote DNA

PROKARYOTE DNA:• Prokaryotes do not have a nucleus so there

DNA is found in the cytoplasm.• Most Prokaryotes have a single circular DNA

molecule that contains nearly all the cell’s genetic information.

• Prokaryotes have about 1000 times less DNA than an Eukaryote. (although an E coli bacterium’s DNA contains approximately 4,639,221 base pairs)

Prokaryote DNA versus Eukaryote DNA continued…

EUKARYOTE DNA:• Eukaryotes DNA is a bit more complicated, 1000 X

more than Prokaryotes and is found in the nuclei of the cell in the form of a number of chromosomes.

• The nucleus of a human cell contains more than 1 meter of DNA (coiled into 46 tiny chromosomes!)

• Eukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called Chromatin.

More on Eukaryotic DNA…

• Chromatin consists of DNA that is tightly coiled around proteins called Histones.

• Together the DNA and histone molecules form a beadlike structure called a Nucleosomes.

• Nucleosomes seem to be able to fold enormous lengths of DNA into the tiny space available in the cell nucleus.

DNA Replication

• The use of existing DNA as a template for the synthesis of new DNA strands

• DNA replicates by "unzipping" along the two strands, breaking the hydrogen bonds which link the pairs of nucleotides. Each half then serves as a template for nucleotides available in the cell which are joined together by DNA polymerase.

More on DNA Replication…

• The double helix structure of DNA explains how DNA could be copied or duplicated.

• Each strand (side) has all the information needed to reconstruct the other half by the mechanism of base pairing.

• In Prokaryotes replication begins at a single point in the chromosome.

• In Eukaryotes replication occurs at hundreds of places.• Replication proceeds in both directions until each

chromosome is completely copied.• The sites where separation and replication occur are

called replication forks.

DNA Polymerase

• Is the principal enzyme involved in DNA replication.

• It joins individual nucleotides to produce a DNA molecule, which is, of course, a polymer.

• It also “proofreads” each new DNA strand, helping to maximize the odds that each molecule is a perfect copy of the original DNA.

RNA (ribonucleic acid)

Is different than DNA because:• Single strand of nucleotides.• Uracil replaces thymine• its sugar is ribose instead of

deoxyribose.• Involved in protein synthesis• found in nucleus, cytoplasm & at

the ribosomes of a cell.• Has 3 types: messenger RNA,

Transfer RNA, Ribosomal RNA

3 Types of RNA

1. Messenger RNA – (mRNA) carries copies of the instructions for assembling amino acids into proteins to the ribosome. Serve as messengers from the DNA to the rest of the cell.

2. Transfer RNA – (tRNA) transfers each amino acid from the cytoplasm to the ribosome as it is specified by the coded messages in mRNA.

3. Ribosomal RNA – (rRNA) make up ribosomes in conjunction with several dozen proteins.

Protein Synthesis

• The process by which the genetic code puts together proteins in the cell.

• Both DNA and RNA is used to carry-out this process.

• There are two parts of protein synthesis -transcription

-translation

Transcription (DNA Transcription)• Process by which one part of the

nucleotide sequence of DNA is copied into a complementary sequence of RNA.

• Takes place in the nucleus of a cell.

• During Transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA.

Transcription (DNA Transcription)

• RNA polymerase doesn’t bind to DNA just anywhere to start copying DNA.

• The enzyme will bind only to regions of DNA known as Promoters, which have specific base sequences. So in effect they are signals in the DNA to tell the enzyme where to bind, there are also signals in the RNA to stop transcription.

• DNA sequence is copied into a functional RNA (mRNA) "messenger RNA"

Transcription (DNA Transcription)

• Once the RNA is copied from the DNA it has to be finished.

• DNA had 2 different types of sequences of nucleotides: Introns and Exons

• Introns are not involved in coding for proteins.• Exons are the codes for building proteins.• So to finish the RNA into the message for building

proteins the Introns are cut out and the Exons are spliced together to form mRNA.

• The coding mRNA sequence can be described as a unit of three nucleotides called a codon.

Translation (protein synthesis)

• The mRNA leaves the nucleus and travels to the cytoplasm, where it encounters cellular bodies called ribosomes.

• The ribosome binds to the mRNA at the start codon (AUG) that is recognized only by the initiator tRNA the anticodon.

• The ribosome proceeds to the elongation phase of protein synthesis which takes place in the cytoplasm of the cell.

Translation continues.

• The ribosome moves from codon to codon along the mRNA. Amino acids are added one by one, translated into polypeptide chain forming a protein.

• At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide chain from the ribosome.

1.Draw and label protein synthesis include both procedures of transcription and translation together as one complete process2.Must be done on one page3.Required parts and structures include: -nucleus

-ribosome's -cytoplasm

-DNA ( deoxyribose, phosphate, adenine, thymine, cytosine, and guanine) -RNA: both mRNA and tRNA ribose, phosphate, adenine, uracil, cytosine, guanine, codon, and anticodon -amino acids: (example = val, phe or ala) pg 303 - polypeptide chain

PROTEIN SYNTHESIS DRAWING ASSIGNMENT -- USE PAGES 301, 305 AND

306 TO HELP YOU

Protein Review

• Proteins are made from amino acids

• There are 20 different types of amino acids that are used to make proteins. ( much like the letters of the alphabet are used to form words)

• Chains of amino acids linked by peptide bonds called polypeptides

Genetic Coding

• Since RNA is constructed from four types of nucleotides, there are 64 possible triplet sequences or codons (4x4x4). Three of these possible codons specify the termination of the polypeptide chain. They are called "stop codons". That leaves 61 codons to specify only 20 different amino acids. Therefore, most of the amino acids are represented by more than one codon.

Reading the Genetic Code

• To read the codon ACG- Read A from the left-hand side of the table Read C across the top of the table Read G as the fourth line in that block, on the right-hand side of the table

• The codon ACG codes for the amino acid thr (threonine)

Chemical Reactions in Organic Compounds (Dehydration Synthesis & Hydrolysis)

• Dehydration synthesis is the process of removing a hydrogen atom and a hyrdoxyl group (-OH) from two combining monosaccharides to form a larger disaccharide.

Hydrolysis

• Hydrolysis is the reverse process, in which water is "split" in the process of breaking polysaccharides down into smaller saccharides.