Nucleic acids 2006-2007
Nucleic Acids Information storage
Nucleic Acids: Function: u genetic material stores information w genes w blueprint for building proteins n DNA DNA RNA proteins transfers information w blueprint for new cells w blueprint for next generation proteins
A C T G T G A C A C A T G
Nucleic Acids: Examples: u RNA (ribonucleic acid) single helix u DNA (deoxyribonucleic acid) double helix Structure: u monomers = nucleotides DNA RNA
Nucleotides: 3 parts u nitrogen base (C-N ring) u pentose sugar (5C) ribose in RNA deoxyribose in DNA u phosphate (PO 4 ) group Nitrogen base I m the A,T,C,G or U part! Are nucleic acids charged molecules?
Types of nucleotides: 2 types of nucleotides u different nitrogen bases Purine = AG Pure silver! u purines double ring N base adenine (A) guanine (G) u pyrimidines single ring N base cytosine (C) thymine (T) uracil (U)
Nucleic polymer: Backbone u sugar to PO 4 bond u phosphodiester bond new base added to sugar of previous base polymer grows in one direction u N bases hang off the sugar-phosphate backbone Dangling bases? Why dangling?
Pairing of nucleotides: Nucleotides bond between DNA strands u H bonds u purine :: pyrimidine u A :: T 2 H bonds u G :: C 3 H bonds Matching bases? Why is this important?
DNA molecule: Double helix u H bonds between bases join the 2 strands A :: T C :: G H bonds? Why is this important?
Copying DNA: Replication u 2 strands of DNA helix are complementary have one, can build other have one, can rebuild the whole Hey! If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain? Matching halves? Why is this a good system?
When does a cell copy DNA? When in the life of a cell does DNA have to be copied? u cell reproduction mitosis u gamete production meiosis
DNA replication: It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material. James Watson Francis Crick 1953
1953 1962 Watson and Crick and others
Maurice Wilkins and the first clear X-ray images of DNA 1953 1962
Rosalind Franklin (1920-1958) Photo 51
Interesting note Ratio of A-T::G-C affects stability of DNA molecule u 2 H bonds vs. 3 H bonds u biotech procedures more G-C = need higher T to separate strands u high T organisms many G-C u parasites many A-T (don t know why)
Another interesting note ATP Adenosine triphosphate u modified nucleotide adenine (AMP) + P i + P i + +
HELIXHELIX
DNA and Proteins as Tape Measures of Evolution: Sequences of genes and their protein products document the hereditary background of an organism Linear sequences of DNA molecules are passed from parents to offspring We can extend the concept of molecular genealogy to relationships between species Molecular biology has added a new measure to the toolkit of evolutionary biology
Analyzing polypeptide sequence:
Analyzing polypeptide sequence: way cool! Two species that appear to be closely related based on fossil and molecular evidence should also be more similar in DNA and protein sequences than are more distantly related species. Scientists can compare the sequence of 146 amino acids in the polypeptide chain of human hemoglobin to the sequences in five other vertebrates. Humans and gorillas differ in just 1 amino acid, while humans and frogs differ in 67 amino acids. Human Rhesus Gibbon monkey
Macromolecule Review. Hey now!
Carbohydrates: Structure / monomer u monosaccharide Function u energy u raw materials u energy storage u structural compounds glycosidic bond Examples u glucose, starch, cellulose, glycogen
Lipids: Structure / building block u glycerol, fatty acid, cholesterol, H-C chains Function u energy storage u membranes u hormones Examples u fat, phospholipids, steroids ester bonds (in a fat)
Proteins: Structure / monomer u amino acids u levels of structure Function u enzymes u transport u signals Examples u defense u structure u receptors u digestive enzymes, membrane channels, insulin hormone, actin peptide bond
Nucleic acids: Structure / monomer u nucleotide Function u information storage & transfer Examples u DNA, RNA phosphodiester bond
Let s build some DNA, baby!
Building the polymer:
RNA & DNA: RNA u single nucleotide chain DNA u double nucleotide chain N bases bond in pairs across chains u spiraled in a double helix double helix 1st proposed as structure of DNA in 1953 by James Watson & Francis Crick (just celebrated 50th anniversary in 2003!)
Information polymer: Function well suited info. storage molecule damage to one strand can be repaired by addition of bases that match the complementary strand u series of bases encodes information like the letters of a book u stored information is passed from parent to offspring need to copy accurately u stored information = genes genetic information Passing on information? Why is this important?