4 Translation1

7/29/2019 4 Translation1

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Translation

the process by which a messenger RNA

molecule specifies the linear sequence of

synthesis


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Ribosome iscomposed of

rRNA and proteins

Translation utilizes codons

Non copy DNA: 5ATG GTA TGC AAT TAA

Transcription

mRNA: 5AUG GUA UGC AAU UAA

codon


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A sequence of three adjacent nucleotidesconstituting the genetic code that determines

the insertion of a specific amino acid in apolypeptide chain (mRNA) during protein

synthesis or the signal to stop proteinsynthesis

Four base pair

y64 codons

y21 amino acids

y1 start (methionine)

y3 stop codons


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Translaton

Non copy DNA: 5ATG GTA TGC AAT TAA

Transcription

mRNA: 5AUG GUA UGC AAU UAA

Translation

Protein MetValCysAsnstop

A protein is composed of one or more

chains of linked amino acids called

polypeptides. Twenty different amino

acids are commonly found in proteins.


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Four main components of

translation1. mRNA: Determinesthe

aminoacidsequenceandbringsribosomalsubunitstogether.

2. Ribosomes: thecellularor anellewhere roteinsynthesistakesplace.

y

Madeup

of

two

subunits:

y OnelargeandonesmalltheywraparoundthemRNA.

Four components of translation

3. tRNA: BindstothemRNAribosomeandmediatesthetranslationofmRNAcodons toaminoacids.

y SmallestRNAmolecule.

4. AminoacyltRNA

synthetases:

enzymesthatcatalyzethe

bondingoftRNA toanaminoacid.


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Three steps in Translation.

2. Elongation

.

Initiationy .

y tRNA carrying methionine attach to

template

y Second ribosomal subunit attach


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ymRNA bind to

small subunit(40s)

y large subunit

(60s)

Elongation

chain.

y Corresponding aa are dependent on

m emp a e


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Anticodon


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Termination, ,

y No corresponding aa

y Ribosome release from the mRNA

y Polypeptide chain or protein is

released to do its function


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Do you know?

y If give a copy strand of DNA, could you give

the mRNA transcript, anticodon, and finally the

protein

TAC CAT ACG TTT AAA GCA ACG ACC GCA ACC CAC ATT copy DNA

AUGGUAUGC AAA UUUCGU UGC UGG CGU UGGGUGUAA mRNA

UAC CAUACGUUU AAA GCA ACG ACC GCA ACCCAC AUU anticodon

- - - - - - - - - -


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Wouldthesinglechangeinfluence

Sickled Cell anemia (Hgb S)

y Sin le nucleotide chan e

of Thymine to Adenine

result in a valine aa

instead of glutamine

y Result in distorted red

blood cells

y Block blood flow

y Damage organs

y Cause anemia fewer

red blood cells


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Sickled cell anemiaTGA GGA CTC CTC

ACU CCU GAG GAG Normal

thr pro glu glu

TGA GGA CAC CTC

ACU CCU GUG GAG Mutant

Cause missence, single point mutationEffect is a biochemical muation

Mutation is defined as an alteration in DNA

sequence

Substitution

Insertion

Deletion


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Substitution mutationy Defined as changing one base pair to another

y Occurs due to misreading of DNA polymerase

y Classification based on type of molecular change

y Missence mutation mutated codon codes for

y Nonsence mutation mutated codon codes for a

stop codon and the gene is not completely produced

y Silent mutation - mutated codon codes for same aa

Insertion or Deletion mutationy Defined as removal or addition of one or more base

pairs

y Loop of nucleotides in template or copy strand

y DNA polymerase miss these then there is a deletionin new strand

y DNA polymerase adds nucleotides resulting in aninsertion in new strand

y Frameshift mutation insertion or deletion of one ormore base pairs in a gene, shifting the codon readingframe in all codons that follow the mutation site.


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Classification of mutations basedon phenotypic effects

y Loss-of-function mutation eliminate the function of a geneproduct

y Point mutation or loss or insertion of one or more base pairs

y Gain-of-function mutation mutation of gene results in a newunc on

y Point mutation or loss or insertion of one or more base pairs

y Neutral mutation mutation occurring in non-coding region ofgenome

Types of mutations

y Visible mutation affects morphological trait or qualitativetrait

y Nutritional mutation no longer synthesize a particular aaor vitamin

y Fungi and Bacteria

oc em ca mu a on a ec e we - e ng an surv vaof an individual

y Sickle-cell anemia and hemophilia

y Lethal mutation interrupt a process essential for life

y Huntingtons disease


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Moving genes result in mutation

yTransposons jumping genes that move

within and between chromosomes

yAll organisms have transposable elements

y Jumping gene can insert within the coding

region of a gene thus altering its function


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Down Syndrome on somatic chromosomes

urners syn rome on sex c romosomes

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