How Proteins are Made

How Proteins are How Proteins are MadeMade

How RNA differs from DNAHow RNA differs from DNA

1st- RNA 1st- RNA consists of a consists of a single single strandstrand of of nucleotidesnucleotides instead of the instead of the 2 strands 2 strands found in DNAfound in DNA

RNRNAA

DNDNAA


2nd- RNA 2nd- RNA nucleotides nucleotides contain the five-contain the five-carbon sugar carbon sugar riboseribose rather rather than the sugar than the sugar deoxyribosedeoxyribose found in DNAfound in DNA

One less Oxygen


3rd- RNA has 3rd- RNA has

A, C, G, and A, C, G, and U- U- UracilUracil (U (U bonds with A bonds with A because no T in because no T in RNA)RNA)

Example: DNA ATGCATCG

RNA UACGUAGC

Transcription and Transcription and TranslationTranslation

The instruction for The instruction for making a protein making a protein are are transferredtransferred from a gene to an from a gene to an RNA molecule in a RNA molecule in a process called process called transcriptiontranscription..

Transcription and Transcription and TranslationTranslation

Cells then use Cells then use 22 different types of RNA different types of RNA to read the instructions to read the instructions on the RNA molecule on the RNA molecule and put together the and put together the amino acidsamino acids that that make up the protein in make up the protein in a process called a process called translationtranslation..

Transcription: Making Transcription: Making RNARNA

Step 1Step 1: Transcription : Transcription begins when begins when RNARNA polymerases bind to polymerases bind to the gene’s the gene’s promoterpromoter (a specific sequence of (a specific sequence of DNA that acts as a DNA that acts as a ““startstart” signal for ” signal for transcription.transcription.


Step 2Step 2: RNA : RNA polymerases then polymerases then unwindunwind and and separate the 2 separate the 2 strands of the strands of the double helix, double helix, exposing the DNA exposing the DNA nucleotidesnucleotides on on each strand.each strand.


Step 3: RNA Step 3: RNA polymerase polymerase addsadds and then and then links links complementary complementary RNA nucleotides RNA nucleotides as it “as it “readsreads” the ” the gene.gene.

TranscriptionTranscription

MessengerMessenger RNA RNA ((mRNAmRNA) is a form of ) is a form of RNA that carries the RNA that carries the instructions for instructions for making a making a proteinprotein from a from a genegene and and deliversdelivers it to the it to the site of translation.site of translation.

Transcripton & CodonsTranscripton & Codons The RNA instructions are written as a series of The RNA instructions are written as a series of

three-nucleotide sequences on the mRNA three-nucleotide sequences on the mRNA called codons.called codons.

Example: UAU UGU AGGExample: UAU UGU AGG

Codes for: Tyrosine Cysteine ArginineCodes for: Tyrosine Cysteine Arginine

****See Codon Chart on page 211, figure 4****See Codon Chart on page 211, figure 4

mRNA Codon ChartmRNA Codon Chart

****TAKS QUESTIONS********TAKS QUESTIONS****

A short chain of DNA has the A short chain of DNA has the nucleotide sequence ATA CCG. nucleotide sequence ATA CCG. Its complementary mRNA Its complementary mRNA nucleotide sequence isnucleotide sequence is

A. TAT GCC

D. UAU GGC

C. TUT GCC

B. UAU GCC


What is the maximum number of What is the maximum number of amino acids that could be coded amino acids that could be coded for by a section of mRNA with for by a section of mRNA with the sequence GUCCAGAACUGU?the sequence GUCCAGAACUGU?

A. 3

D. 12

C. 6

B. 4


If a codon reads UGU, what is its If a codon reads UGU, what is its anticodon?anticodon?

A. TCT

D. ACA

C. UGU

B. AGA


What is the name of the amino What is the name of the amino acid coded by AGU? (See figure acid coded by AGU? (See figure 4, page 211)4, page 211)

______________________________________Serine

Translation: Assembling Translation: Assembling ProteinsProteins

TransferTransfer RNA RNA ((tRNAtRNA) molecules ) molecules are are singlesingle strands of RNA strands of RNA that temporarily that temporarily carry a carry a specificspecific amino acid on one amino acid on one end.end.


An An anticodonanticodon is is a three-a three-nucleotide nucleotide sequence on a sequence on a tRNA that is tRNA that is complementacomplementaryry to an to an mRNAmRNA codon.codon.


RibosomalRibosomal RNA ( RNA (rRNArRNA) ) molecules are RNA molecules molecules are RNA molecules that are part of the that are part of the structurestructure of of ribosomesribosomes..

Steps of TranslationSteps of Translation

Step 1Step 1: The ribosomal subunits, the : The ribosomal subunits, the mRNAmRNA, and the , and the tRNAtRNA carrying carrying methioninemethionine bind together. bind together.

Step 2Step 2: The tRNA carrying the : The tRNA carrying the amino acid specified by the codon amino acid specified by the codon in the in the AA site site arrivesarrives..


Step 3Step 3: A : A peptidepeptide bond forms bond forms between between adjacentadjacent amino acids. amino acids.

Step 4Step 4: The tRNA in the : The tRNA in the PP site site detachesdetaches and leaves its amino and leaves its amino acid behind.acid behind.


Step 5Step 5: The tRNA in the : The tRNA in the AA site site moves to the moves to the PP site, the tRNA site, the tRNA carrying the amino acid specified by carrying the amino acid specified by the the codoncodon in the A site arrives. in the A site arrives.

Step 6Step 6: A : A peptidepeptide bond is formed. bond is formed. The tRNA in the The tRNA in the PP site detaches and site detaches and leavesleaves its amino acid behind. its amino acid behind.


Step 7Step 7: The process is repeated : The process is repeated until a until a stopstop codon is reached. codon is reached. The ribosomes complex falls The ribosomes complex falls apartapart. The newly made protein . The newly made protein is is releasedreleased..

Section 2: Gene Regulation Section 2: Gene Regulation and Structureand Structure

In In eukaryoteseukaryotes, many genes , many genes are interrupted by are interrupted by intronsintrons (long segments of nucleotides (long segments of nucleotides that have that have nono coding coding information.information.


ExonsExons are the are the portions of a portions of a gene that are gene that are translatedtranslated (expressed) (expressed) into into proteinsproteins..


The The exonsexons that that remain are remain are ““stitchedstitched” ” back together by back together by the the spliceosomesspliceosomes to form a smaller to form a smaller mRNA molecule mRNA molecule that is then that is then translatedtranslated..

TAKS Test PrepTAKS Test Prep

1. Which cellular function does this model represent?

A. Transcription

D. DNA replication

C. Transformation

B. Translation


2. Which part of the model represents a codon?F. A

J. D

H. C

G. B*** Codons are associated with mRNA


3.What does the part labeled E represent?A. Ribosome

D. Transfer RNA

C. Messenger RNA

B. Growing protein chain

The circles represent amino acids which are what proteins are made up of.

PracticePractice

DNA- A C C T G T A A C G A G C C A G T T DNA- A C C T G T A A C G A G C C A G T T

mRNA- U G GmRNA- U G G

tRNA- A C CtRNA- A C C

Codons- Tryp Codons- Tryp

A C A U U G C U C G G U C A A C A U U G C U C G G U C A A A

U G U A A C G A G C C A G U U G U A A C G A G C C A G U UU

Thre Leu Leu GlycThre Leu Leu Glyc

How Proteins are Made

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