Introduction to Introduction to Molecular GeneticsMolecular Genetics

Introduction to Introduction to Molecular GeneticsMolecular Genetics

Rowan UniversitySpring Semester

Mrs. Patricia Sidelsky2008

Rowan UniversitySpring Semester

Mrs. Patricia Sidelsky2008

Regulatory RNAsRegulatory RNAs

http://www.dnalc.org/ddnalc/dna_today/episodes/5/episode5.html

Molecular GeneticsMolecular Genetics

Molecular genetics and molecular biology are almost synonomous terms

A “ hybrid” science The change in the understanding

of life has led to a revolution in the field of Biology

Molecular genetics and molecular biology are almost synonomous terms

A “ hybrid” science The change in the understanding

of life has led to a revolution in the field of Biology

Molecular GeneticsMolecular Genetics

The result of an amalgam of a variety of physical and biological sciences

Genetics, microbiology, biochemistry, physical chemistry, and physics

Driven by the need to understand the underlying principles of life and the reactions of life

The result of an amalgam of a variety of physical and biological sciences

Genetics, microbiology, biochemistry, physical chemistry, and physics

Driven by the need to understand the underlying principles of life and the reactions of life

Max DelbruckIlustrates the blend in scientific

disciplines

Max DelbruckIlustrates the blend in scientific

disciplines German immigrant Originally trained in physical

chemistry and theoretical physics Converted to molecular genetics Collaborated with Salvador Luria

on the characterization and genetics of bacteriophages

German immigrant Originally trained in physical

chemistry and theoretical physics Converted to molecular genetics Collaborated with Salvador Luria

on the characterization and genetics of bacteriophages

Molecular Genetics - Origins

Molecular Genetics - Origins

Thomas Hunt Morgan- Columbia University

The physical nature of the gene A discovery in 1910 changed the course of

genetics Developed experimental model for the

study of modern genetics- the fruit fly – Drosophila melanogaster

The white eyed male mutant appeared in a culture of flies in the fly room and this was the beginning of a search for mutants

Thomas Hunt Morgan- Columbia University

The physical nature of the gene A discovery in 1910 changed the course of

genetics Developed experimental model for the

study of modern genetics- the fruit fly – Drosophila melanogaster

The white eyed male mutant appeared in a culture of flies in the fly room and this was the beginning of a search for mutants

White and Wild typeWhite and Wild type

Easy to cultivate Prolific progeny Small and

inexpensive Large polytene

chromosomes Diploid number 8 Many mutations

Easy to cultivate Prolific progeny Small and

inexpensive Large polytene

chromosomes Diploid number 8 Many mutations

Hermann Joseph MullerHermann Joseph Muller

X rays cause mutations

Produced a variety of flies with phenotypes such asvestigial

X rays cause mutations

Produced a variety of flies with phenotypes such asvestigial

Alfred Sturdevant produced the first genetic map from linkage

experiments

Alfred Sturdevant produced the first genetic map from linkage

experiments Genes were

related to position on the chromosome map

Mutants were related to differences in the appearance of the polytene chromosomes due to staining

Genes were related to position on the chromosome map

Mutants were related to differences in the appearance of the polytene chromosomes due to staining

DNA as Genetic MaterialTransformation

DNA as Genetic MaterialTransformation

Griffith in 1928 observed the change of non-virulent organisms into virulent ones as a result of “transformation” MacLeod and McCarty in 1944

showed that the transforming principle was DNA

Griffith in 1928 observed the change of non-virulent organisms into virulent ones as a result of “transformation” MacLeod and McCarty in 1944

showed that the transforming principle was DNA

Figure 11.1

Transforming principleTransforming principle

Avery, McLeod, and McCartyAvery, McLeod, and McCarty

Proof of the Transforming Principle

Proof of the Transforming Principle

Chemical analysis of sample containing the transforming principle showed that the major component was a deoxyribose -containing nucleic acid

Physical measurements show that the sample contained a highly viscous substance having the properties of DNA

Incubatyion with trypsin or chymotrypsin, enzymes that catalzye protein hydrolysis or with ribonuclease( RNase), an enzyme that catalyzes RNA hydrolysis did not affect the transforming principle

Incubation with DNase, an enzyme that catalyzes DNA hydrolysis inactivates the transforming principle

Chemical analysis of sample containing the transforming principle showed that the major component was a deoxyribose -containing nucleic acid

Physical measurements show that the sample contained a highly viscous substance having the properties of DNA

Incubatyion with trypsin or chymotrypsin, enzymes that catalzye protein hydrolysis or with ribonuclease( RNase), an enzyme that catalyzes RNA hydrolysis did not affect the transforming principle

Incubation with DNase, an enzyme that catalyzes DNA hydrolysis inactivates the transforming principle

TransfectionTransfection

DNA as Genetic Material( of viruses)DNA as Genetic Material( of viruses) Hershey and Chase, 1952

used bacteriophage T2 infection as model DNA labeled with 32P;protein coat labeled

with 35S Only DNA entered cell but both new DNA

and protein coats synthesized and incorporated into new viruses indicating that DNA had the genetic information for synthesis of both of these viral components

Hershey and Chase, 1952 used bacteriophage T2 infection as model DNA labeled with 32P;protein coat labeled

with 35S Only DNA entered cell but both new DNA

and protein coats synthesized and incorporated into new viruses indicating that DNA had the genetic information for synthesis of both of these viral components

T2 phageT2 phage

Chargaff’s RuleChargaff’s Rule

Analyzed DNA from a variety of sources and improved both the separation and quantitation of the DNA bases

[C] = [G] and [A] = [T] Today this is applied to the G=C or

G.C pairs. Scientists describe the G+C content in organisms

Analyzed DNA from a variety of sources and improved both the separation and quantitation of the DNA bases

[C] = [G] and [A] = [T] Today this is applied to the G=C or

G.C pairs. Scientists describe the G+C content in organisms

G+CG+C

Now used as a means of classifying bacteria

G+C content varies in Gram Positive Bacteria

G+C content ranges from .27 in Clostridium to .76 for Sarcina

Most Eukaryotes have a value close to 50%

Now used as a means of classifying bacteria

G+C content varies in Gram Positive Bacteria

G+C content ranges from .27 in Clostridium to .76 for Sarcina

Most Eukaryotes have a value close to 50%

G+C contentG+C content

G+C content = [G] +[C] / all bases in DNA

G+C content = [G] +[C] / all bases in DNA

The Race for the Double Helix

The Race for the Double Helix

Rosalind Franklin and Maurice Wilkins at Kings College

Studied the A and B forms of DNA

Rosalind’s famous x-ray crystallography picture of the B form held the secret, but she didn’t realize its significance

Rosalind Franklin and Maurice Wilkins at Kings College

Studied the A and B forms of DNA

Rosalind’s famous x-ray crystallography picture of the B form held the secret, but she didn’t realize its significance

Rosalind FranklinRosalind Franklin

Technically and scientifically a gifted scientist

Focused on the A form of DNA and missed the double helix

Technically and scientifically a gifted scientist

Focused on the A form of DNA and missed the double helix

The Race for the Double Helix

The Race for the Double Helix

Watson and Crick formed an unlikely partnership

A 22 year old PhD and a thirty + PhD “want to be” embarked on a model making venture at Cambridge

Used the research of other scientists to determine the nature of the double helix

Watson and Crick formed an unlikely partnership

A 22 year old PhD and a thirty + PhD “want to be” embarked on a model making venture at Cambridge

Used the research of other scientists to determine the nature of the double helix

Nucleic Acid CompositionDNA and RNA

Nucleic Acid CompositionDNA and RNA

DNA – Basic Moleculesa. Purines – adenine and guanineb. Pyrmidines – cytosine and thyminec. Sugar – Deoxyribosed. Phosphate phosphate group

http://www.dnai.org/index.htm -  DNA background

DNA – Basic Moleculesa. Purines – adenine and guanineb. Pyrmidines – cytosine and thyminec. Sugar – Deoxyribosed. Phosphate phosphate group

http://www.dnai.org/index.htm -  DNA background

NucleotidesNucleotides

Sugar Phosphate Base

Adenine and guanine are purines

Thymine and Cytosine are pyrimidines

Sugar Phosphate Base

Adenine and guanine are purines

Thymine and Cytosine are pyrimidines

Deoxyribose in DNADeoxyribose in DNA

Double HelixDouble Helix Two polynucleotide strands joined by

phosphodiester bonds( backbone) Complementary base pairing in the center of the

moleculeA= T and C G – base pairing. Two hydrogen

bonds between A and T and three hydrogen bonds between C and G.

A purine is bonded to a complementary pyrimidine Bases are attached to the 1’ C in the sugar by a

glycosidic linkage At opposite ends of the strand – one strand has the

3’hydroxyl, the other the 5’ hydroxyl of the sugar molecule

Two polynucleotide strands joined by phosphodiester bonds( backbone)

Complementary base pairing in the center of the molecule

A= T and C G – base pairing. Two hydrogen bonds between A and T and three hydrogen bonds between C and G.

A purine is bonded to a complementary pyrimidine Bases are attached to the 1’ C in the sugar by a

glycosidic linkage At opposite ends of the strand – one strand has the

3’hydroxyl, the other the 5’ hydroxyl of the sugar molecule

DNA StructureDNA Structurehttp://www.johnkyrk.com/DNAanatomy.html - DNA structure

Double helix( continued)Double helix( continued)

The double helix is right handed – the chains turn counter-clockwise.

As the strand turn around each other they form a major and minor groove.

The is a distance of .34nm between each base

The distance between two major grooves is 3.4nm or 10 bases

The diameter of the strand is 2nm

The double helix is right handed – the chains turn counter-clockwise.

As the strand turn around each other they form a major and minor groove.

The is a distance of .34nm between each base

The distance between two major grooves is 3.4nm or 10 bases

The diameter of the strand is 2nm

Complementary Base Pairing

Complementary Base Pairing

Adenine pairs with Thymine

Cytosine pairs with Guanine

Adenine pairs with Thymine

Cytosine pairs with Guanine

The end view of DNAThe end view of DNA

This view shows the double helix and the outer backbone with the bases in the center.

An AT base pair is highlighted in white

This view shows the double helix and the outer backbone with the bases in the center.

An AT base pair is highlighted in white

Double helix and anti-parallel

Double helix and anti-parallel

DNA is a directional molecule The complementary strands run in

opposite directions One strand runs 3’-5’ The other strand runs 5’ to 3’( the end of the 5’ has the

phosphates attached, while the 3’ end has a hydroxyl exposed)

DNA is a directional molecule The complementary strands run in

opposite directions One strand runs 3’-5’ The other strand runs 5’ to 3’( the end of the 5’ has the

phosphates attached, while the 3’ end has a hydroxyl exposed)

Prokaryote DNAProkaryote DNA

Tightly coiled Coiling maintained by molecules similar to

the coiling in eukaryotes Circular ds molecule Borrelia burgdoferi ( Lyme Disease )has a

linear chromosome Other bacteria have multiple chromosomes Agrobacterium tumefaciens ( Produces

Crown Gall disease in plants) has both circular and linear

Tightly coiled Coiling maintained by molecules similar to

the coiling in eukaryotes Circular ds molecule Borrelia burgdoferi ( Lyme Disease )has a

linear chromosome Other bacteria have multiple chromosomes Agrobacterium tumefaciens ( Produces

Crown Gall disease in plants) has both circular and linear

Prokaryote chromosomes

Prokaryote chromosomes

Circular DNACircular DNA

MitochondriaMitochondria

Mitochondrial DNA( mt DNA)

16,500 base pairs 37 genes 24 encode RNA Defects lead to

diseases that are related to energy

Mitochondrial DNA( mt DNA)

16,500 base pairs 37 genes 24 encode RNA Defects lead to

diseases that are related to energy

Chloroplast DNAChloroplast DNA

Chloroplast DNA( cp DNA) is larger than mitochondrial DNA

195,000 bp Genes for photosynthesis Cp ribosomal RNAs

Chloroplast DNA( cp DNA) is larger than mitochondrial DNA

195,000 bp Genes for photosynthesis Cp ribosomal RNAs

Heavy and Light NMeselson and Stahl experiment

Heavy and Light NMeselson and Stahl experiment

In the first generation of E. coli, all the DNA was heavy

After one generation, the DNA was half heavy and half light

In the first generation of E. coli, all the DNA was heavy

After one generation, the DNA was half heavy and half light

DNA Replication –Semi Conservative

DNA Replication –Semi Conservative

DNA ReplicationDNA Replication

DNA opens at an Ori ( origin of replication)

Combination of many enzymes coordinate the replicative process

Template strand used to make the copy

DNA polymerases read the template and match the complementary base

DNA opens at an Ori ( origin of replication)

Combination of many enzymes coordinate the replicative process

Template strand used to make the copy

DNA polymerases read the template and match the complementary base

Degradation of DNADegradation of DNA

Endonucleases cleave DNA and RNA, by cutting between individual bonds

Some endonucleases cleave one strand some cleave both strands at a specific point or sequence( restriction nucleasess)

Endonucleases cleave DNA and RNA, by cutting between individual bonds

Some endonucleases cleave one strand some cleave both strands at a specific point or sequence( restriction nucleasess)

The Flow of Genetic Information

The Flow of Genetic Information

from one generation to the next DNA stores genetic information Information is duplicated by

replication and is passed on to next generation

from one generation to the next DNA stores genetic information Information is duplicated by

replication and is passed on to next generation

The Flow of Genetic Information within a single

cell

The Flow of Genetic Information within a single

cell

Process called gene expression DNA divided into genes

transcription yields a ribonucleic acid (RNA) copy of specific genes

translation uses information in messenger RNA (mRNA) to synthesize a polypeptide Also involves activities of transfer RNA (tRNA)

and ribosomal RNA (rRNA)

Process called gene expression DNA divided into genes

transcription yields a ribonucleic acid (RNA) copy of specific genes

translation uses information in messenger RNA (mRNA) to synthesize a polypeptide Also involves activities of transfer RNA (tRNA)

and ribosomal RNA (rRNA)

Flow of Genetic Information in Cells

Flow of Genetic Information in Cells

Nucleic Acid StructureRibonucleic Acid (RNA)Nucleic Acid StructureRibonucleic Acid (RNA)

Polymer of nucleotidesContains the bases

adenine, guanine, cytosine and uracil

Sugar is riboseMost RNA molecules are

single stranded

Polymer of nucleotidesContains the bases

adenine, guanine, cytosine and uracil

Sugar is riboseMost RNA molecules are

single stranded

RNARNA

Types of RNAa. Messengerb. Transferc. Ribosomald. micro RNAs ( regulatory RNAs)

Types of RNAa. Messengerb. Transferc. Ribosomald. micro RNAs ( regulatory RNAs)

Messenger RNAMessenger RNA

16s rRNA16s rRNA

Ribosomal RNARibosomal RNA

tRNAtRNA

RNA virusesRNA viruses

Reoviruses Retroviruses Enteroviruses

Reoviruses Retroviruses Enteroviruses

Genomics of RNA virusesGenomics of RNA viruses

Genomes - + RNA - RNA segmented RNA Ds RNA

Genomes - + RNA - RNA segmented RNA Ds RNA

Polio virusPolio virus

Polio Virus- + ss RNA virus Polio Virus- + ss RNA virus

ViroidsViroids Infectious agents that causes

disease in higher plants Small circular loops of RNA The viroid RNA is infectious and

its is not surrounded by a capsid Viroids RNA replicates

autonomously

Infectious agents that causes disease in higher plants

Small circular loops of RNA The viroid RNA is infectious and

its is not surrounded by a capsid Viroids RNA replicates

autonomously

ViroidsViroids

PSTV Potato SpindleTuber Viroid

PSTV Potato SpindleTuber Viroid

Proteins are polymersProteins are polymers

Proteins are polymers of amino acids. They are molecules with diverse structures and functions.

Polymers are made up of units called monomers

The monomers in proteins are the 20 amino acids

Proteins are polymers of amino acids. They are molecules with diverse structures and functions.

Polymers are made up of units called monomers

The monomers in proteins are the 20 amino acids

Protein FactsProtein Facts

Proteins: Polymers of Amino Acids Proteins are polymers of amino acids.

They are molecules with diverse structures and functions.

Each different type of protein has a characteristic amino acid composition and order.

Proteins range in size from a few amino acids to thousands of them.

Folding is crucial to the function of a protein and is influenced largely by the sequence of amino acids.

Proteins: Polymers of Amino Acids Proteins are polymers of amino acids.

They are molecules with diverse structures and functions.

Each different type of protein has a characteristic amino acid composition and order.

Proteins range in size from a few amino acids to thousands of them.

Folding is crucial to the function of a protein and is influenced largely by the sequence of amino acids.

Proteins: Polymers of Amino Acids

Proteins: Polymers of Amino Acids

Each different type of protein has a characteristic amino acid composition and order.

Proteins range in size from a few amino acids to thousands of them.

Folding is crucial to the function of a protein and is influenced largely by the sequence of amino acids.

Each different type of protein has a characteristic amino acid composition and order.

Proteins range in size from a few amino acids to thousands of them.

Folding is crucial to the function of a protein and is influenced largely by the sequence of amino acids.

Proteins are complex molecules

Proteins are complex molecules

They have levels of structure Structure based upon the

sequence of the amino acids

They have levels of structure Structure based upon the

sequence of the amino acids

Polar side chainsPolar side chains

Non Polar Hydrophobic side chains

Non Polar Hydrophobic side chains

Electrical charged hydrophilic

Electrical charged hydrophilic

Function of Proteins - continued

Function of Proteins - continued

Enzymes – Biological catalysts Transport of small molecules – Albumin

and haptoglobin Transport of oxygen – hemoglobin and

myoglobin Membrane proteins – to assist in support Channels in membranes – to allow the

passage of molecules or ions Electron carriers in electron transport in

the production of ATP

Enzymes – Biological catalysts Transport of small molecules – Albumin

and haptoglobin Transport of oxygen – hemoglobin and

myoglobin Membrane proteins – to assist in support Channels in membranes – to allow the

passage of molecules or ions Electron carriers in electron transport in

the production of ATP

Functions( continued)iFunctions( continued)i

Clotting proteins Immune proteins to fight infectious

agents Histones – DNA binding proteins Toxins to repel or kill other organisms Bacteriocins – molecules produced by

bacteria against bacteria

Clotting proteins Immune proteins to fight infectious

agents Histones – DNA binding proteins Toxins to repel or kill other organisms Bacteriocins – molecules produced by

bacteria against bacteria

Functions of proteinsFunctions of proteins

Hormones – Growth hormone Receptors – to Receive information so that

cell can communicate with other cells Neurotransmitters – messenger molecules

– to send information between neurons Cytoskeleton – actin, myosin, and

collagen – the structure of connective tissue and muscles

Antibodies – Immunoglobulins to fight disease

Hormones – Growth hormone Receptors – to Receive information so that

cell can communicate with other cells Neurotransmitters – messenger molecules

– to send information between neurons Cytoskeleton – actin, myosin, and

collagen – the structure of connective tissue and muscles

Antibodies – Immunoglobulins to fight disease

Four levels of Protein Structure

Four levels of Protein Structure

There are four levels of protein structure: primary, secondary, tertiary, and quaternary.

The precise sequence of amino acids is called its primary structure.

The peptide backbone consists of repeating units of atoms: N—C—C—N—C—C.

Enormous numbers of different proteins are possible.

There are four levels of protein structure: primary, secondary, tertiary, and quaternary.

The precise sequence of amino acids is called its primary structure.

The peptide backbone consists of repeating units of atoms: N—C—C—N—C—C.

Enormous numbers of different proteins are possible.

The causes of Tertiary structure

The causes of Tertiary structure