G

Leucine

Serine

Tyrosine

Stop

Cysteine

Stop

Tryptophan

Leucine

Proline

Histidine

GlutamineArginine

Phenylalanine

GlycineGlutamic acid

Aspartic acid

Alanine

Valine

Arginine

Serine

Lysine

Asparagine

Threonine

MethionineIsolucine

A

G U

A C

G

U

AC

G

U

AC

G

U

AC

G

U

AC

G

U

AC

G

U

AC

G

U

AC

GU AC G

U AC

G

UA

C

G

U

AC

G

U

AC

G

C

C

A

G

C

C

A

G

A

AG

AG

C

CG A

G

C

CA

U

U

U

UU

U

U

U

What is the amino acid sequence for the codons: GCA UAC CCC GUA?alanine tyrosine proline valine

UUUUUCUUAUUG

UCUUCCUCAUCG UAU

UAC

Animated by Jeff Christopherson

Phenylalanine Leucine Serine Tyrosine Stop Cysteine Stop Tryptophan

Leucine Proline Histidine Glutamine Arginine

Isoleucine Methionine Threonine Asparagine Lysine Serine Arginine

Valine Alanine Aspartic Acid Glutamic Acid Glycine

Phenylalanine

UUUUUC

Leucine

UUAUUG

Serine

UCUUCCUCAUCG

Tyrosine

UAUUAC

Stop

UAAUAGUGA

Cysteine

UGUUGC

Stop

UGA

Tryptophan

UGG

Leucine

CUUCUCCUACUG

Proline

CCUCCCCCACCG

Histidine

CAUCAC

Glutamine

CAACAG

Arginine

CGUCGCCGACGG

Isoleucine

AUUAUCAUA

Methionine

AUG

Threonine

ACUACCACAACG

Asparagine

AAUAAC

Lysine

AAAAAG

Serine

AGUAGC

Arginine

AGGAGA

Valine

GUUGUCGUAGUG

Alanine

GCUGCCGCAGCG

Aspartic Acid

GAUGAC

Glutamic Acid

GAAGAG

Glycine

GGUGGCGGAGGG

A

G U

A C

G

U

AC

G

U

AC

G

U

AC

G

U

AC

G

U

AC

G

U

AC

G

U

AC

GU AC G

U AC

G

UA

C

G

U

AC

G

U

AC

G

C

C

A

G

C

C

A

G

AG

AG

AG

C

CG A

G

C

CA

U

U

U

UU

U

U

U

A. The Structure of RNA

B. Types of RNA

C. Transcription

D. RNA Editing

E. The Genetic Code

F. Translation

G. The Roles of RNA and DNA

H. Genes and Proteins

RNA and Protein Synthesis

from to to make up

Concept Map

also called which functions to also called also called which functions towhich functions to

can be

RNA

Messenger RNA Ribosomal RNA Transfer RNA

mRNA Carry instructions rRNACombine

with proteins tRNABring

amino acids toribosome

DNA Ribosome Ribosomes

RNADNA

RNApolymerase

Transcription

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

The Genetic Code

Messenger RNA

Messenger RNA is transcribed in the nucleus.

Transfer RNA

The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.

mRNA Start codon

Ribosome

Methionine

Phenylalanine tRNALysine

Nucleus

Translation

mRNA

The Polypeptide “Assembly Line”The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.

mRNARibosome

Translation direction

Lysine tRNA

tRNA

Ribosome

Growing polypeptide chain

mRNA

Completing the PolypeptideThe process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.

Translation (continued)

Interest Grabber

• Determining the Sequence of a Gene

• DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.

Interest Grabber continued

1. Copy the following information about Protein X: Methionine—Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP.

2. Use Figure 12–17 on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence.

3. Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence.

4. Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y.

5. Did this single deletion cause much change in your protein? Explain your answer.