Transcription and Translation Getting Genetic Information out of DNA out of DNA

Transcription and TranslationTranscription and TranslationGetting Genetic InformationGetting Genetic Information

out of DNAout of DNA

I.I. Transcription (DNA Transcription (DNA RNA) RNA)

A.A. BackgroundBackground

1.1. DNA codes for protein productionDNA codes for protein production

a.a. cannot leave nucleuscannot leave nucleus

b.b. must send out a “messenger”must send out a “messenger”

B.B. RNA – the chemical messengerRNA – the chemical messenger

1.1. differences from DNA:differences from DNA:

a.a. single strandedsingle stranded

b.b. ribose sugarribose sugar

c.c. Uracil (U) instead of (T)Uracil (U) instead of (T)



2.2. RNA’s Role...RNA’s Role...

a.a. get DNA code to ribosome get DNA code to ribosome for for protein synthesisprotein synthesis

3.3. Types of RNATypes of RNA

a.a. Messenger RNA (mRNA)Messenger RNA (mRNA)

1.1. RNA copy of DNA codeRNA copy of DNA code

2.2. takes copy to ribosometakes copy to ribosome




b.b. Transfer RNA (tRNA)Transfer RNA (tRNA)

1.1. transfers amino acids transfers amino acids ((protein building protein building

blocksblocks) ) to protein to protein construction construction site site (ribosome)(ribosome)




c.c. Ribosomal RNA (rRNA)Ribosomal RNA (rRNA)

1.1. structural RNA structural RNA component of component of

ribosomesribosomes

2.2. Ribosomes = Ribosomes =

rRNA and ProteinrRNA and Protein



DNA | RNA DNA | RNA

AA –– U U

C C –– GG

T T –– AA

G G –– CC

DNA Template

RNA Copy of DNA Message


C.C. Process of TranscriptionProcess of Transcription

1.1. Enzymes unzip DNA Enzymes unzip DNA (just like in (just like in replication)replication)

2.2. RNA nucleotides bind to the RNA nucleotides bind to the exposed DNA nucleotidesexposed DNA nucleotides

a.a. AGC TAA CCG AGC TAA CCG (DNA) (DNA)

UCG AUU GGC UCG AUU GGC (RNA) (RNA)

3.3. RNA strand breaks free, leaves RNA strand breaks free, leaves nucleus, heads to ribosomenucleus, heads to ribosome

II.II. Translation (RNA Translation (RNA Protein) Protein)

* mRNA is translated into polypeptide (protein)* mRNA is translated into polypeptide (protein)

*amino acids are joined together by peptide *amino acids are joined together by peptide bondsbonds

*polypeptide continues growing until a “stop *polypeptide continues growing until a “stop codon” is reachedcodon” is reached


A.A. Translating the MessageTranslating the Message

1.1. every 3 letters in RNA codes for every 3 letters in RNA codes for ONE amino acidONE amino acid

a.a. 3 letters = “codon”3 letters = “codon”

2.2. every tRNA molecule is carrying every tRNA molecule is carrying ONE amino acidONE amino acid

a.a. 3 exposed bases at the 3 exposed bases at the bottom bottom are called “anticodons”are called “anticodons”


B.B. Steps in TranslationSteps in Translation

1.1. mRNA binds to the ribosomemRNA binds to the ribosome

2.2. tRNA brings amino acid to tRNA brings amino acid to ribosomeribosome

3.3. exposed mRNA codon attracts exposed mRNA codon attracts complementary tRNA anticodoncomplementary tRNA anticodon

4.4. mRNA and tRNA join, ribosome mRNA and tRNA join, ribosome holds both in placeholds both in place


B.B. Steps in TranslationSteps in Translation

5.5. ribosome slides down to next ribosome slides down to next codoncodon

6.6. the next tRNA joins, ribosome the next tRNA joins, ribosome creates a peptide bond creates a peptide bond

between the between the two amino acids of the two amino acids of the 2 adjacent 2 adjacent tRNA molecules.tRNA molecules.

*polypeptide (protein) continues growing until *polypeptide (protein) continues growing until a “stop codon” is reacheda “stop codon” is reached

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Transcription and Translation Getting Genetic Information out of DNA out of DNA