MolecularBiology

FrancescaStomeo

IMBB2017RAB,Kigali- RwandaMay02– 13,2017

Molecularbiologyisthestudyofbiologyatamolecularlevel,especiallyDNAandRNA- replication,transcription,translation,andcellfunction.

Molecularbiologyoverlapswithotherareasofbiologyandchemistry,particularlygenetics(effectofgeneticdifferencesonorganisms)andbiochemistry (chemicalsubstancesandvitalprocessesoccurringinlivingorganisms).

Molecularbiologyistheconvergenceofvarious,previouslydistinctbiologicalandphysicaldisciplines:biochemistry,genetics,cellbiology,microbiology,virologyandphysics.

MolecularbiologyisthebranchofbiologythatdealswiththemanipulationofDNAorRNAsothatitcanbesequenced,detected,modified,orexpressed.

Thetechniquesofmolecularbiologyareappliedtomanyfields

– Genomics– Cellbiology– Microbiology– Biotechnology– Diagnostics– Therapeutics– Forensics– Agriculture

Somecoretoolsofmolecularbiology

DNApurification

Polymerasechainreaction

Gelelectrophoresis

Restrictionanalysis

DNAsequencing

Bioinformatics

DNAstructureandreplication

• Deoxyribonucleicacid

• Macromolecule(averagehumanchromosomehas5cmofDNA)

• Containsgeneticinstructionsfor developmentandfunctioningofallknownlivingorganisms

• Long-termstorageofinformation

• ContainstheinstructionsneededtoconstructRNAmoleculesandproteins

• DNAsegmentsthatcarrythisgeneticinformationarecalledgenes

DNA

Figu

re 4

-3 M

olec

ular

Bio

logy

of t

he C

ell(

© G

arla

nd S

cien

ce 2

008)

• DNA is normally double stranded

• Two strands held together by H bonds between bases

• A single strand of DNA has an orientation (5’ → 3’)

• In double stranded DNA, the two strands have opposite orientation

• There are four bases A (adenine), C (cytosine), G (guanine), T (thymine)

• Specific base pairing- Base A always pairs with T- Base C always pairs with G

• The sequence of one strand defines the sequence of the second strand. The two strands are said to be ‘complimentary’

• Information is stored in the sequence of bases

• Double stranded DNA resembles a ladder- Rails = sugar/phosphate - Rungs = base pairs (bp)

• DNA building blocks = 4 nucleotides (phosphate/sugar/base)

• DNAisanucleicacid,madeoflongchainsofnucleotides

DNAisapolymerofnucleotides

Nucleotide

Phosphate group

Nitrogenous baseSugar

Polynucleotide Sugar-phosphate backboneDNA nucleotide

Phosphategroup

Nitrogenous base(A, G, C, or T)

Thymine (T)

Sugar(deoxyribose)

Campbelletal.(2003)BIOLOGYconceptsandconnections.

5’END

3’END

3’and5’endsofDNAmovie

http://www.youtube.com/watch?v=p835L4HWH68

• Eachstrandofthedoublehelixisorientedintheoppositedirection

5¢end 3¢end

3¢end 5¢end

P

P

P

PP

P

P

P

Campbelletal.(2003)BIOLOGYconceptsandconnections.

• DNAhasfourkindsofbases,A,T,C,andG

Pyrimidines

Thymine (T) Cytosine (C)

Purines

Adenine (A) Guanine (G)

Campbelletal.(2003)BIOLOGYconceptsandconnections.

• InDNAreplication,thestrandsseparate– Anenzyme(polymerase)useeachstrandasatemplatetoassemblethenewstrands

DNA REPLICATION

DNAreplicationdependsonspecificbasepairing

Parental moleculeof DNA

Both parental strands serveas templates

Two identical daughtermolecules of DNA

Nucleotides

A

Campbelletal.(2003)BIOLOGYconceptsandconnections.

http://www.tokresource.org/tok_classes/biobiobio/biomenu/dna_replication/index.htm

Startcodon

RNA

Transcribed strand

StopcodonTranslation

Transcription

DNA

Polypeptide

TheDNAistranscribedintoRNA,whichistranslatedintothepolypeptide

• RNAisalsoanucleicacid

– RNA has a slightly different sugar

– RNA has U instead of T

Phosphategroup

Nitrogenous base(A, G, C, or U)

Uracil (U)

Sugar(ribose)

Thankyou

FrancescaStomeof.stomeo@cgiar.org

IMBB2017RAB,Kigali- RwandaMay02– 13,2017