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Protein Synthesis Consists of 2 main steps Step 1: Transcription Step 2: Translation

Central Dogma Proteins DNA RNA Transcription Translation Step 1 Step 2 Occurs at the Ribosome Occurs in the Nucleus

Transcription Step 1 DNA RNA Occurs in the Nucleus

RNA is different from DNA in 3 ways What is RNA? RNA is different from DNA in 3 ways

The sugar is Ribose instead of deoxyribose

RNA is Single stranded instead of double stranded

G C C G T A A U Thymine is replaced by Uracil Let’s make an RNA strand How to code DNA into mRNA In RNA There is no Thymine Adanine bonds to Uracil A – U G C C G Uracil Adenine T A Let’s make an RNA strand DNA A T G C mRNA A U U A C G U G

Types of RNA Messenger RNA (mRNA) Ribosomal RNA (rRNA) There are 3 types of RNA: Messenger RNA (mRNA) Carry copies of instructions for the assembly of amino acids into proteins Serve as “messengers” from DNA to the rest of the cell Ribosomal RNA (rRNA) Helps build ribosomes Transfer RNA (tRNA) Transfers the amino acid to the ribosome C10L10C12

Step 2 of protein synthesis TRANSLATION

During translation, the nitrogen bases of mRNA tell the cell which amino acids (building blocks of proteins) are needed to build a protein (polypeptide).

mRNA bases are read in groups of 3 called codons mRNA bases are read in groups of 3 called codons. Each codon codes for an amino acid. Example: RNA Strand: U C G C A C G G U Reads as: UCG – CAC – GGU (3 codons) Represents the amino acids: Serine – Histidine – Glycine

example: UCU, UCC, UCA, and UCG all code for the amino acid amINO aCIDS There are only 20 different amino acids, but 64 different codon possibilities, so several codons might represent 1 amino acid. example: UCU, UCC, UCA, and UCG all code for the amino acid SERINE There is also one codon AUG that is called the START codon because it starts protein synthesis. There are 3 stop codons that stop protein synthesis.

Lets practice mRNA AUG UGA CCU Amino Acid   mRNA GCG GAU UGC Amino Acid  

AUG START Methionine U C A G Second Base of Codon First Base of Codon Third Base of Codon UUU Phenylalanine phe UCU Serine ser UAU Tyrosine tyr UGU Cysteine cys UUC UCC UAC UGC UUA Leucine leu UCA UAA STOP UGA UUG UCG UAG UGG Tryptophan trp CUU CCU Proline pro CAU Histadine his CGU Arginine arg CUC CCC CAC CGC CUA CCA CAA Glutamine gln CGA CUG CCG CAG CGG AUU Isoleucine ile ACU Threonine thr AAU Asparagine asn AGU AUC ACC AAC AGC AUA ACA AAA Lysine lys AGA AUG Methionine Met (start) ACG AAG AGG GUU Valine val GCU Alanine ala GAU Aspartic Acid asp GGU Glycine gly GUC GCC GAC GGC GUA GCA GAA Glutamic Acid glu GGA GUG GCG GAG GGG AUG START Methionine C10L10C12

Lets practice mRNA AUG UGA CCU Amino Acid mRNA GCG GAU UGC Amino Acid   Met (Start) Stop Pro mRNA GCG GAU UGC Amino Acid   Asp Cys Ala C10L10C12

Translation During translation the mRNA strand synthesized during transcription will be used to make a protein.

How is a protein (polypeptide) made? The mRNA leaves the nucleus and attaches to a ribosome C10L10C12

How is a protein (polypeptide) made? Translation begins at the START codon (AUG) on the mRNA. The codons in mRNA match anticodons in tRNA. TRNA transfers amino acids to the ribosome when they are called for by the codons in mRNA. C10L10C12

How is a protein (polypeptide) made? The ribosome moves down the mRNA strand, codon by codon, and each tRNA brings an amino acid that is added to the growing protein (polypeptide). C10L10C12

C10L10C12