dna and gene expression

8/8/2019 DNA and Gene Expression

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DNA and GeneDNA and Gene

ExpressionExpression


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DNADNA

Deoxyribonucleic AcidDeoxyribonucleic Acid

Double helixDouble helix

Carries genetic informationCarries genetic information Located in the nucleusLocated in the nucleus

The monomer is a nucleotideThe monomer is a nucleotide

A phosphateA phosphate

A ribose sugarA ribose sugar A nitrogenous baseA nitrogenous base


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What are the bases in DNAWhat are the bases in DNA

AA adenineadenine

TT thyminethymine

CC cytosinecytosine GG guanineguanine

Base pair rulesBase pair rules


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Where is DNA located in the Cell?Where is DNA located in the Cell?


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Where are the genes located?Where are the genes located?

Genes are located onGenes are located onthe chromosomes.the chromosomes.

Every species has aEvery species has adifferent number ofdifferent number ofchromosomes.chromosomes.

There are two typesThere are two types

of chromosomes:of chromosomes:autosomes and sexautosomes and sexchromosomeschromosomes


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Genes are located on the chromosomesGenes are located on the chromosomes

which are found in the nucleus of a cell.which are found in the nucleus of a cell.When a cell is undergoing cellWhen a cell is undergoing cell

reproduction, the chromosomes arereproduction, the chromosomes arevisible. Chromosomes appear when thevisible. Chromosomes appear when thechromatin condenses and become visible.chromatin condenses and become visible.

Most of the time (90%) the geneticMost of the time (90%) the geneticmaterial in the form of chromatin.material in the form of chromatin.

A genome is the complete geneticA genome is the complete geneticinformation contained in an individual.information contained in an individual. (gene + chromosome)(gene + chromosome)


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What is gene expression?What is gene expression?

Gene expression is theGene expression is theactivation of a geneactivation of a genethat results in athat results in a

protein.protein.


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Gene expression takes place differentlyGene expression takes place differentlyin prokaryotes and eukaryotes.in prokaryotes and eukaryotes.

What is a prokaryotes? Eukaryotes?What is a prokaryotes? Eukaryotes?

ProkaryotesProkaryotes

No membrane boundNo membrane boundorganelles (nucleus)organelles (nucleus)

More primitiveMore primitiveorganismsorganisms

Only one circularOnly one circular

chromosomechromosome

Bacteria are the onlyBacteria are the onlyorganisms that areorganisms that areprokaryotes.prokaryotes.

EukaryotesEukaryotes

Membrane boundMembrane boundorganelles ( specialize inorganelles ( specialize infunctionfunction nucleus,nucleus,mitochondria, chloroplast)mitochondria, chloroplast)

Chromosomes are in pairsChromosomes are in pairs

and not circularand not circular

All organisms that are notAll organisms that are notbacteria: protist, fungi,bacteria: protist, fungi,plants and animalsplants and animals


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In Eukaryotes, following mitosis or meiosis, DNAIn Eukaryotes, following mitosis or meiosis, DNArecoils but certain regions remain relaxed forrecoils but certain regions remain relaxed for

transcription. The areas of relaxed DNA aretranscription. The areas of relaxed DNA arecalledcalled euchromatineuchromatin..

Transcription is theTranscription is the

Reading of the DNA andReading of the DNA andChanging the code toChanging the code to

mRNA.mRNA.

Translation is changingTranslation is changing

The mRNA into a trait byThe mRNA into a trait by

Using tRNA to interpret theUsing tRNA to interpret the

mRNA.mRNA.


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DNA in eukaryotes has regions of coding andDNA in eukaryotes has regions of coding andnoncoding DNA. The regions of DNA that codenoncoding DNA. The regions of DNA that codefor proteins or traits are calledfor proteins or traits are called EXONSEXONS, while, whilethe regions that do not code for proteins arethe regions that do not code for proteins arecalledcalled INTRONS.INTRONS.

cytoplasmcytoplasm


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In prokayotes, transcription andIn prokayotes, transcription andtranslation occur in the cytoplasm.translation occur in the cytoplasm.

In eukaryotes, transcription occurs insideIn eukaryotes, transcription occurs insidethe nucleus in a two step sequence ofthe nucleus in a two step sequence ofevents.events.

PrePre--mRNA includes both introns and exons formRNA includes both introns and exons forthe gene.the gene.

mRNA is only the coding portion (exons).mRNA is only the coding portion (exons).

Translation occurs in the cytoplasm at theTranslation occurs in the cytoplasm at the

ribosomes.ribosomes. Reminder: The are three (3) types of RNAReminder: The are three (3) types of RNA

Messenager (mRNA)Messenager (mRNA)

Transfer (tRNA)Transfer (tRNA)

Ribsomal (rRNA)Ribsomal (rRNA)


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TranslationTranslation RNARNA

Single strandedSingle stranded Does not contain thymineDoes not contain thymine

but has uracil instead.but has uracil instead.

tRNA carries 3 base pairtRNA carries 3 base paircode for specific aminocode for specific amino

acid.acid. Amino acids composeAmino acids compose

polypeptid chains.polypeptid chains.

One or more polypeptideOne or more polypeptidechains compose achains compose aproteinprotein

proteins provide theproteins provide theblueprints for ourblueprints for ourcharacteristics andcharacteristics and

functions.

functions.


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In Prokaryotes there are three (3)In Prokaryotes there are three (3)

regulatory elements that control generegulatory elements that control geneexpression.expression.

1.1. Structural genesStructural genes genes that code for agenes that code for aspecific polypeptide (protein).specific polypeptide (protein).

2.2. PromoterPromoter DNA segment that recognizesDNA segment that recognizesRNA polymerase.RNA polymerase.

3.3. OperatorOperator element that serves as a bindingelement that serves as a bindingsite for an inhibitor protein that blockssite for an inhibitor protein that blockstranscription.transcription.


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Enhancer ControlEnhancer Control

Eukaryote genes on aEukaryote genes on aDNA strand also haveDNA strand also havenoncoding controlnoncoding controlsequences thatsequences that

facilitate transcription.facilitate transcription. These are calledThese are called

enhancers.enhancers.

Transcription factorsTranscription factors

are additional proteinsare additional proteinsthat bind to RNAthat bind to RNApolymerase andpolymerase andenhancers to help withenhancers to help withtranscription.transcription.


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Cell DifferentiationCell Differentiation

Cell differentiationCell differentiation is the developmentis the developmentof cells into cells with specializedof cells into cells with specializedfunctions.functions.

Examples: muscle cells, liver cell, red bloodExamples: muscle cells, liver cell, red bloodcellscells

As organisms grow and develop, organsAs organisms grow and develop, organs

and tissues develop to produce aand tissues develop to produce acharacteristic form. The process is callcharacteristic form. The process is callmorphogenesis.morphogenesis.


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Homeotic GenesHomeotic Genes H

omeotic genes are regulatoryH

omeotic genes are regulatorygenes that determine wheregenes that determine wherecertain anatomical structures,certain anatomical structures,such as appendages, willsuch as appendages, will

develop in an organism duringdevelop in an organism duringmorphogenesis.morphogenesis.

These seem to be the masterThese seem to be the mastergenes of developmentgenes of development

Normal Mutant with legsgrowing out of head


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HomeoboxHomeobox

InIn DrosophilaDrosophila (fruit flies)(fruit flies)the specific DNA sequencethe specific DNA sequencewithin a homeotic genewithin a homeotic genethat regulates patterns ofthat regulates patterns of

development is thedevelopment is thehomeoboxhomeobox..

The same or very similarThe same or very similarhomeobox sequences havehomeobox sequences have

been found in many otherbeen found in many othereukaryotic organismseukaryotic organisms


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CancerCancer

Leading cause of death in the UnitedLeading cause of death in the UnitedStatesStates

A genetic disease caused by a mutation inA genetic disease caused by a mutation inthe genes that control cell divisionthe genes that control cell division


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TumorTumor abnormal proliferation of cellsabnormal proliferation of cellsthat results from uncontrolled, abnormalthat results from uncontrolled, abnormalcell divisioncell division

BenignBenign a tumor that remains within a massa tumor that remains within a mass

Malignant tumorMalignant tumor-- uncontrolled dividing cellsuncontrolled dividing cellsthat invade and destroy healthy tissuethat invade and destroy healthy tissueelsewhere in the bodyelsewhere in the body

MetastasisMetastasis spread of cancer cells beyondspread of cancer cells beyondtheir original sitetheir original site


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Kinds of CancerKinds of Cancer

CarcinomasCarcinomas grow in skin and tissues thatgrow in skin and tissues thatline the organs of the bodyline the organs of the body

Example: lung and breastExample: lung and breast SarcomasSarcomas grow in bone and musclegrow in bone and muscle

tissuetissue

LymphomasLymphomas solid tumors that grow insolid tumors that grow intissues that form blood cellstissues that form blood cells

Example: leukemiaExample: leukemia


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What Causes Cancer?What Causes Cancer? Mutations that alter the genes codingMutations that alter the genes coding

for growth factors.for growth factors.May occur spontaneouslyMay occur spontaneously

Result from exposure to anResult from exposure to an carcinogencarcinogen

( any substance that increases the risk of( any substance that increases the risk ofcancer.)cancer.)

Usually there is more than oneUsually there is more than onemutation.mutation.

There are two types of genes thatThere are two types of genes thatcontrol cell divisioncontrol cell divisionProtoProto--oncogensoncogens

Tumor suppressing genes (p53 gene)Tumor suppressing genes (p53 gene)

dna and gene expression

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