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PROTEIN PROTEIN SYNTHESISSYNTHESISCHAPTER 10 section 4 CHAPTER 10 section 4

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Starting with DNAStarting with DNA• DNA ‘s codeDNA ‘s code must be must be copiedcopied

and taken to the cytoplasmand taken to the cytoplasm• In the cytoplasm, this In the cytoplasm, this code code

must be readmust be read so so amino acidsamino acids can be assembled to make can be assembled to make polypeptides (proteins)polypeptides (proteins)

• This process is called This process is called PROTEIN SYNTHESISPROTEIN SYNTHESIS

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RNA Differs from DNARNA Differs from DNA

• RNA has a sugar RNA has a sugar riboseribose

DNA has a sugar DNA has a sugar deoxyribosedeoxyribose

• RNA contains the base RNA contains the base uracil (Uuracil (U))DNA has DNA has thymine (T)thymine (T)

• RNA molecule is RNA molecule is single-strandedsingle-strandedDNA is DNA is double-strandeddouble-stranded

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. Three Types of Three Types of RNARNA

• Messenger RNA (mRNA)Messenger RNA (mRNA) copies DNA’s code & carries copies DNA’s code & carries the genetic information to the the genetic information to the ribosomesribosomes

• Ribosomal RNA (rRNA)Ribosomal RNA (rRNA), along , along with protein, makes up the with protein, makes up the ribosomesribosomes

• Transfer RNA (tRNA)Transfer RNA (tRNA) transfers transfers amino acids to the ribosomes amino acids to the ribosomes where proteins are where proteins are synthesizedsynthesized

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Protein SynthesisProtein Synthesis The production or

synthesis of proteins happens in two phases: Transcription & Translation

DNADNA RNARNA ProteinProtein

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• During transcription, RNA polymerase enzyme binds to a promoter on DNA and separates the DNA strands

• A promoter is a specific nucleotide sequence of DNA where the RNA polymerase binds and starts transcription.

• RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA

• Once the Polymerase reaches a terminal signal (the stop sign), the RNA polymerase releases the RNA and DNA

TranscriptionTranscription

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The Genetic Code• Three adjacent nucleotides

(letters) in mRNA codes for a specific amino acid (word)

• A codon designates an amino acid

• An amino acid may have more than one codon

• There are 20 amino acids, but 64 possible codons

• Some codons tell the ribosome to stop translating

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The Genetic Code

•Use the code by reading from the center to the outside•Example: AUG codes for Methionine

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TranslationTranslation• Translation is the process of decoding

the mRNA into a polypeptide chain• Ribosomes read mRNA 1 codon at a

time and construct the proteins• tRNA carrying the amino acid

specified by the codon binds and a peptide bond is formed between the two amino acids.

• This process continues until a stop codon is reached.

• The ribosome then falls apart.

http://learn.genetics.utah.edu/content/molecules/transcribe/

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Codons and Anticodons

• The 3 bases of an anticodon are complementary to the 3 bases of a codon

• Example: Codon ACU

Anticodon UGA

UGA

ACU

copyright cmassengale 12

http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__how_translation_works.html

PROTEIN SYNTHESIS ANIMATION

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

http://www.youtube.com/watch?v=itsb2SqR-R0

http://www.zerobio.com/drag_oa/protein/overview.htm