Genetic Material Structure of DNA Replication of DNA Function of Genes Molecular Biology of the Gene Spring Althoff Reference: Mader & Windelspecht Ch. 12) Lec 17

 Is ___________, therefore accounting for species  ___________ so every cell gets a copy during cell division  Stores information needed to ________ the cell  __________ mutations, thus accounting for evolution of new species What does DNA do?

1869- JOHANN MIESCHER: discovered nuclei from pus cells contained the chemical nuclein…a chemical rich in phosphorus but no sulfur (thus distinguishing it from a protein) Subsequent work by other chemists said “nuclein” contain acidic substances called nucleic acid This was followed by fleshing out that there are 2 types of nucleic acids: DNA - deoxyribonucleic acid RNA - ribonucleic acid Early Discoveries related to DNA…

Early 1900s, it was determined that nucleic acids consisted of only _______________ __________________: molecules composed of  ______________________  ______________________  ______________________ Early Discoveries related to DNA …con’t

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This “limited” base set (only 4 nucleotides) lead to a conclusion that the nucleotides could _____ be responsible for the genetic material. They thought it was the ___________ component because they had identified 20 amino acids…thus, allowing for seemingly more variability. This view was held until the late ______. Early Discoveries related to DNA …con’t

In _____, bacteriologist ___________________ while working on a vaccine against Streptococcus pneumoniae determined the “_______________” ______________ where heat inactivated S strain bacteria converted the R strain to the virulent S strain. It wasn't until several years later that Griffith's "transforming principle" was identified as ______. Lead researchers to look closer at the _________ nature of genetic material Early Discoveries related to DNA …con’t

Griffith’s Transformation Experiment - A Bacteria encapsulated S strain was virulent (“smooth looking”) Injected live S strain has capsule and caused mice to die

Injected live R strain has no capsule and mice did NOT die Griffith’s Transformation Experiment - B Non-encapsulated R strain was not virulent (“rough looking”)

Injected heat-killed S strain into mice…they did NOT die Griffith’s Transformation Experiment - C Heated encapsulated S strain to kill it

Griffith’s Transformation Experiment - D Live S strain is withdrawn from dead mice Injected heat-killed S strain plus live R strain caused mice to die. Conclusion: “some” substance necessary to the synthesis of a capsule, and therefore, virulent, must have been passed from the dead S strain bacteria to the living R strain transforming the R strain. (rough  smooth colonies)

In _____, OSWALD AVERY, COLIN MACLEOD, and MACLYN MCCARTY published paper demonstrating that DNA was the ____________ substance. The evidence: 1) DNA from S strain causes R strain bacteria to be transformed 2) Enzymes that degrade proteins cannot prevent transformation 3) Enzymatic digestion of the transforming substance with DNase does prevent transformation 4) Molecular weight of the transforming substance is so great that it must contain about _______ nucleotides! Early Discoveries related to DNA …con’t

In ______, ALFRED HERSHEY and MARTHA CHASE conducted experiments with bacteriophages to finally confirm that the “transforming” substance was _____ and not _________ ______________ = viruses that infect bacteria Experimental procedure determined that the DNA of the virus entered the host (bacteria), not the protein. The bacteria then contained all the genetic information needed to produce new viruses Early Discoveries related to DNA …con’t

What are genes made of ? DNA Virus has 2 parts: Capsid (a protein) and DNA (nucleic acid). Hershey and Chase determined DNA part was what the virus was injecting into the bacteria allowing it to take control… because the _____ rules!!! Protein coat - Capsid E. coli

DNA “minute” A _________ G _________ C _________ T _________ DNA – contains 4 different types of nucleotides NITROGEN-CONTAINING BASES PURINES A G PYRIMIDINES C UT DOUBLE RINGS SINGLE RINGS

Erwin ________ and the ______ Austrian _________

DNA “minute” A Adenine T Thymine C Cytosine G Guanine DNA – contains 4 different types of nucleotides Amounts of these always _______ in a cell. In humans cell, 31% Adenine & 31% Thymine Amounts of these always ________ in a cell. In humans cell, 19% Cytosine & 19% Guanine Chargaff’s Rules: 1)_______________________________________________ 2)_______________________________________________

A = Adenine T =Thymine C = Cytosine G = Guanine

___________________ Model Published in _______ Complimentary pairing results in rungs, always A + T and G +C “_________________” a) base pairs can be in any order b) in any order accounts for genetic variability between species c) provides a “copying” mechanism for genetic material

Hydrogen bonds

Always will be these base pairings. The A-T (T-A) or G-C (C-G) pairing

DNA and the next cell During the ________ ( remember lab? ), DNA is copied during INTERPHASE—this is known as _____________________--the process of copying the DNA molecule Old DNA strands (parent cell’s DNA molecule) serve as template for new DNA One strand ends up in the parent cell, with a new matching strand…and one strand ends up in the daughter cell with a new matching strand.

DNA Replication -3 steps  ______________—the double helix structure is unwound AND unzipped, forming 2 strands  ___________________________ —new complementary nucelotides, always present in the nucleus, are “positioned” correctly to match the “old” strand present  ______________ —the “old” and “new” complementary nucelotides join to form new strands. Thus, each daughter DNA molecule contains an “old” strand on one side and a “new” strand on the other

DNA Replication…some extra points Step  carried out by an enzyme complex known as _________________ THE DAUGHTER DNA DOUBLE HELIX HAS THE SAME _________________ __________ AS THE PARENT DNA DOUBLE HELIX HAD ORIGINALLY.

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The Function of Genes Early 1900s, _____________________ suggested relationship between inheritance and metabolic diseases. Garrod among first to hypothesize a link between ________ and _________ In _______, George Beadle and Edward Tatum worked with red bread mold fungus ( Neurospora crassa ): work lead them to conclude that each gene specifies the synthesis of one enzyme. That is known as the… _________________________ hypothesis. E 1 E 2 E 3 E 4 E 5 E 6 A  B  C  D  E  F  G

Genes _________ a Polypeptide One-gene-on-one enzyme hypothesis suggested that genetic mutation causes a change in structure of a protein In 1940s, LINUS PAULING and HARVEY ITANO studied the hemoglobin molecule in red blood cells to determine if there was a structural difference in normal vs. diseased RBCs. VERNON INGRAM did more follow-up work They determined that a gene is a segment of DNA that _____________________________ _________ in a polypeptide of a protein.

Refinement of a hypothesis…. one-gene-one enzyme hypothesis from Beadle & Tatum’s work ________________________ hypothesis from Pauling, Itano, Ingram’s research

From DNA to RNA to Protein Geneticists have confirmed many times over that proteins are the link between genotype and phenotype A gene is a segment of DNA that specifies the ______________________ of a protein Among all living things, from _____________ to _____________________…from ___________ ________________ …the same basic processes of specifying polypeptides and expressing genes are found. The gene doesn’t directly control protein synthesis. Instead, it passes on the genetic information onto _____ molecules, which are more directly involved in protein synthesis.

RNA Structure and Function Consist of __________ containing the sugar ribose Is ____________________ A Adenine U Uracil C Cytosine G Guanine

RNA: Major Function RNA is a “helper” to DNA RNA “executes” ____________________ according to the genetic information (“____________”) that DNA provides

RNA: 3 Types  ______________________ (mRNA) is produced in the nucleus during transcription, goes from DNA to ribosomes in the cytoplasm  _____________________ (tRNA) is produced in the nucleus, and “transfers” amino acids to the ribosomes, resulting in a protein  _____________________ (in eukaryotic cells) produced in the nucleolus portion of the nucleus, joins with proteins made in the cytoplasm to form subunits of ribosomes—one large and one small, where they join with other subunits in the cytoplasm where protein synthesis takes place

RNA: Additional points Only a portion of the DNA is “dupped” to produce the single RNA strand. The DNA  RNA strand process is known as ____________________. The RNA  product (i.e, protein synthesis) is known as ___________________. This RNA strand contains the ‘details’ for whatever is suppose to be done—exactly!!!!

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Messenger RNA codons Each amino acid has a GENETIC CODE. There are 20 amino acids. Each “code word” for amino acid is comprised of 3 bases… These are known as CODONS This code is apparently UNIVERSAL to all living things …with few exceptions. Example of value…transfer genes from one organism to another. This is how some commercial and medicinal products can be produced. Example: insulin

RIBOSOMES 3 different proteins being made At same time

Summary of Gene Expression in Eukaryotes  DNA serves as template  mRNA is processed  mRNA moves into cytoplasm, becomes associated with a ribosomes  tRNA with “help” carry amino acids to mRNA NUCLEUS CYTOPLASM NUCLEUS CYTOPLASM

Summary of Gene Expression in Eukaryotes… continued  Anticondon-condon complementary base pairing on ribosome  Polypeptide synthesis, 1 amino acid at a time, takes place  Ribosome can attach to Rough ER  At termination, the ribosome detaches from ER, ribosomal subunits and mRNA disassociate CYTOPLASM ROUGH ER CYTOPLASM

See Mader p232, Fig Transcriptio n Translation