• Genetic Material

• Structure of DNA

• Replication of DNA

• Function of Genes

Molecular Biology of the GeneSpring 2013 - Althoff Reference: Mader & Windelspecht Ch. 12)

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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-killedS strain

into mice…they did NOT die

Griffith’s Transformation Experiment - C

Heated encapsulatedS strain to kill it

Griffith’s Transformation Experiment - D

Live S strain is withdrawn from

dead mice

Injected heat-killed S strainplus live R strain caused

mice to die.

Conclusion: “some” substance necessary to the synthesisof a capsule, and therefore, virulent, must have been passedfrom the dead S strain bacteria to the living R straintransforming 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 viruswas 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 differenttypes of nucleotides

NITROGEN-CONTAINING BASES

PURINESA G

PYRIMIDINESC UT

DOUBLERINGS

SINGLERINGS

Erwin ________ and the ______

• Austrian _________

DNA “minute”

• A Adenine• T Thymine

• C Cytosine• G Guanine

DNA – contains 4 differenttypes 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 orderb) in any order accounts for genetic

variability between speciesc) 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. E1 E2 E3 E4 E5 E6

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

________________________ hypothesisfrom 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 somecommercial and medicinalproducts can be produced. Example: insulin

RIBOSOMES

3 different proteins being

made At same time

Summary of Gene Expression in Eukaryotes

DNA serves as templatemRNA 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

CYTOPLASM

ROUGH ER

CYTOPLASM

See Mader p232, Fig. 12.19

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