central dogma tutorial

8/12/2019 Central Dogma Tutorial

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Genes structure

Chromosomes become visible during ___________ and meiosis.

Chromosomes come in pairs (_______________); one from ______________ and one from

__________

Chromosomes contain genes; each gene is made of two _______________.

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Structure of nucleic acids

Two types: 1. !" # ______________________ $. %!" # ______________________

!ucleotide is the monomer& polynucleotide is the polymer.

'ach monomer consists of : 1. ____________________________ $. ____________________________

. ____________________________

1. hosphate group*ive negative charge to !". hosphates carry negative charges at cellular p+ and give the

nucleotides their acidic character.

$. entose sugar unit

, C sugar

%!" is ribose!" is deo-yribose ( atom at C$ is removed)

. !itrogenous base$ types: 1. urine ("&*) $ rings$. yrimidine (/& T& C) 1 ring

$

%ibose

%ibose


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Base Nucleoside Nucleotide Abbreviation in

RNA / DNA

adenine adenosine adenylic acid "0 d"0guanine guanosine guanylic acid *0 d*0

cytosine cytidine cytidylic acid C0 dC0thymine tymidine thymidylic acid 222222 dT0

uracil uridine uridylic acid /0 222222

"denosine (nucleoside) "denylic acid (nucleotide)

RNA and DNA


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ifferences between %!" and !"

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DNA replication

!" twist into double heli- (4atson and Cric5 model& 16,)The polynucleotides are anti2parallel to each other.

Complementary base pairingouble heli-.

7emiconservative replication

The Meselson-Stahl experimentwas an e-periment by 0atthew 0eselsonand 8ran5lin 7tahlto prove

that !" replication was semiconservative.7emiconservative replication means that when the doublestranded !" heli- was replicated& each of the two double stranded !" helices consisted of onestrand coming from the original heli- and one newly synthesi9ed.

,
http://wiki/Matthew_Meselsonhttp://wiki/Franklin_Stahlhttp://wiki/DNA_replicationhttp://wiki/Semiconservative_replicationhttp://wiki/DNAhttp://wiki/Matthew_Meselsonhttp://wiki/Franklin_Stahlhttp://wiki/DNA_replicationhttp://wiki/Semiconservative_replicationhttp://wiki/DNA


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%eplication of !" is semiconservative: each daughter heli- contains one strand of the parental heli-.(Conservative replication would be where the entire parental double heli- was used as a template for

the formation of an entirely new daughter double heli-).

7emi2conservative replication:

arental _____________________ separate

'ach ________________________ acts as a template "fter replication& each new !" double heli- has one ________ !" strand and one _________

!" strand.

Gene expression / protein synthesis

The central dogma of biology

1. Transcription $. translation . *ene e-pression

1. Transcription: messenger %!" (m%!") is made on a ________ template in the_______________.

$. Translation: m%!" moves into the ____________________& m%!" combines with ribosomes to

direct protein synthesis.

. *ene e-pression: the information in a cistron (genes on !") is used to ma5e a functionalpolypeptide chain by transcription and translation.

he !enetic code

- /sing triplet codon on m%!".

- Three2base (triplet) code on the m%!" codes for ____________________ of polypeptides.

- 1 amino acid is coded by bases& e.g. /// for phenylalanine.


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- ossible combinations: __________ combinations& more than enough for $ amino acids re


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$. rocessing

- rocessed to ribosomal %!" (r%!") ?@& m%!" ,@& and transfer %!" (t%!") 1,@.

m%!"- 8or eu5aryotic m%!"& it consists of __________ and e-ons.

- Antrons will be removed and ____________ are spliced together.

- 8inal m%!"

- The #$ capis a specially altered nucleotideend to the ,B end ofprecursor messenger %!" as foundin eu5aryotes. The process of ,B capping is vital to creating maturemessenger %!"which is then

able to undergo translation. Capping ensures the messenger %!"Bs stability while it undergoestranslation in the process ofprotein synthesis& and is a highly regulated process which occurs in the

nucleus.

%olyadenylationis the covalent lin5age of a poly(") tail to a messenger %!"(m%!")molecule. At ispart of the route to producing mature messenger %!"for translation& in the larger process ofprotein

synthesisto produceproteins.Aneu5aryotic organisms& most messenger %!" molecules end with a

poly2" stretch at theirB ends.The polyadenosine (poly2") tail protects the m%!" molecule frome-onucleasesand is important for transcription termination& for e-port of the m%!" from the nucleus&

and for translation.

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http://wiki/Nucleotidehttp://wiki/5'_endhttp://wiki/Precursor_messenger_RNAhttp://wiki/Eukaryoteshttp://wiki/Mature_messenger_RNAhttp://wiki/Messenger_RNAhttp://wiki/Translation_(genetics)http://wiki/Protein_synthesishttp://wiki/Cell_nucleushttp://wiki/Messenger_RNAhttp://wiki/Moleculehttp://wiki/Mature_messenger_RNAhttp://wiki/Translation_(genetics)http://wiki/Protein_synthesishttp://wiki/Protein_synthesishttp://wiki/Proteinhttp://wiki/Eukaryoteshttp://wiki/3'_endhttp://wiki/Exonucleasehttp://wiki/Nucleotidehttp://wiki/5'_endhttp://wiki/Precursor_messenger_RNAhttp://wiki/Eukaryoteshttp://wiki/Mature_messenger_RNAhttp://wiki/Messenger_RNAhttp://wiki/Translation_(genetics)http://wiki/Protein_synthesishttp://wiki/Cell_nucleushttp://wiki/Messenger_RNAhttp://wiki/Moleculehttp://wiki/Mature_messenger_RNAhttp://wiki/Translation_(genetics)http://wiki/Protein_synthesishttp://wiki/Protein_synthesishttp://wiki/Proteinhttp://wiki/Eukaryoteshttp://wiki/3'_endhttp://wiki/Exonuclease


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t%!"

- t%!" and r%!" are transcript by special genes (cistrons on !")

- "mino acids are carried by t%!" (anticodon) using information in m%!" (codon)

- $ types of t%!"& e.g. t%!"cys& t%!"his& t%!"ala& etc.

- 7ingle strand& folded& clover leaf arrangement

- ne end attached to amino acid

- "nticodon complementary to codon on m%!"

r%!"

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- r%!" maor component of ribosomes

- most abundent ?@

- synthesised in nucleolus: nucleolar organiser.

- '-ported to cytoplasm oin with proteins to form ribosomes

. Transport

r%!"& m%!" and t%!" are transported through __________________ pore to the cytoplasm.

%rotein synthesis

1. $. .

1. t%!" activation

- "n en9yme _________________________ ma5es sure t%!" is carrying the correct amino acid

by its anticodon before it moves to a ribosome.

- Dinding in ,= to = direction

- "T is re


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- "n en9yme peptidyl transferase forms a peptide bond between methionine and the second a.a.

proline.

- The t%!" that was holding methionine is now released from the ribosome& and is free to carryanother methionine molecule.

- %ibosome moves one more triplet codon in ,= to = direction

- 7econd a.a proline occupies 2site and the third t%!" ( ) is entering the "2site

-The process continues until ribosome reaches a Fstop= codon: /""& /*" or /"*.

- The m%!"& ribosome& and t%!" molecules separate& and the polypeptide chain is released.

- Complementary base pairing between anticodons and codons ensure correct se


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1$


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1


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%8 # release factor

. rocessing

- "ccording to the final destination

- Ancludes folding& and adding chains.

- rotein in cell& e.g. haemoglobin& directly from ribosome to cytoplasm.

- 'n9ymes& are made on %'%& transported to *olgi apparatus& modified and pac5aged. Transported

by *olgi vesicles and secreted by e-ocytosis.- 0embranes proteins are made on %'% and remainfused in the membrane.

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8(h) olysomes: speeding up translation

- 7ingle ribosome: a single polypeptide chain 1, amino acids per second

- "ccelerated by polysomes

- , to , ribosomes on the same m%!"

- "t end of m%!"& ribosomes detached and returns to the beginning on the samem%!"

-Garge number of the samepolypeptide chains produced

The figure below shows an electron micrograph and its interpretation. DNAand strings of individual

ribosomes attached to a single mRNA (polyribosome) are visible. The mRNA and RNAPolmolecules are barely visible& and the protein polypeptidesare too small to be seen.

7elf test:

1. Dased on figure below& name the process"________________________

D________________________C________________________

1,


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7tructure ____________________

' ____________________0olecule

8 _____________________

$. Dased on the figure below&

a. (i) !ame the amino acid (ii) 7tate the base se


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. istinguish between a nucleoside and a nucleotide.3. Dy what type of chemical reaction does a phosphodiester bond formH

,. Af one strand of !" has the three base se

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