RNA and PROTEIN SYNTHESISChapter 13-1 & 13-2

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DNA’s code is used to make proteins, right?

Does DNA work alone?

• Check out where DNA holds the code?

• Check out where proteins are made?

• So what other molecule is needed?

A. RNA- the Other Nucleic Acid

• Also made of NUCLEOTIDES

• Sugar is RIBOSE insteadof deoxyribose.

• RNA is SINGLE stranded

• Contains URACIL (U) instead of thymine.

http://images2.clinicaltools.com/images/gene/dna_versus_rna_reversed.jpg

B. KINDS OF RIBONUCLEIC ACID (RNA)1. Ribosomal RNA (rRNA)-Combines with proteins to form

ribosomes

2. Transfer RNA (tRNA)-Matches mRNA codon to add correctamino acids during protein synthesis

3. Messenger RNA (mRNA)-Carries code from DNA to ribosomes

rRNA and t-RNA images from © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reservedmRNA image from http://wps.prenhall.com/wps/media/tmp/labeling/1140654_dyn.gif

RNADNA

RNApolymerase

 C. Transcription – the process of making

RNA from DNA

Section 12-

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

1. An enzyme, RNA polymerase,begins transcription by binding to promoters (like the ‘starting line’)

2. The two strands of DNA are separated 3. Complementary RNA nucleotides are added to one strand (called the template) of DNA

4. When RNA polymerase reaches the termination signal, transcription ends.

5. The RNA is released through the nucleus and DNA reforms.

http://images2.clinicaltools.com/images/gene/dna_versus_rna_reversed.jpg

See a video clip aboutTRANSCRIPTION

(mcgraw-hill animation)

RNA’s require EDITING before use

Image by Riedell

D. Protein Synthesis – genetic info from

DNA is used to make proteins in two steps

1. TRANSCRIPTION (DNA→

RNA)takes place in nucleus

2. TRANSLATION (RNA→ proteins)takes place on ribosomes in cytoplasm

http://www.home-improvement-resource.com/images/architect.jpg

E. Why are proteins important?• Proteins determine the structure &

function of the cell.

• Proteins are made up of one or more polypeptides, each of which consists of a specific sequence of amino acids

F. HOW CAN JUST 4 BASES GIVE DIRECTIONS TO MAKE 20 AMINO ACIDS?

• Message is read in groups of 3 = CODON

example: UCGCACGGU UCG-CAC-GGU- Codons represent different AMINO ACIDS

Serine- Histidine- Glycine

 GG. The Genetic Code- used by most organisms to translate mRNA transcripts into proteins

• 64 possible codons

• Some amino acidshave more than one

codon.

• START= AUG

• 3 codons for STOP

• ANTICODON on tRNA

• matches up with CODON on mRNA

Images modified from © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved

• EACH tRNA carries only one kind of AMINO ACID

H. Translation - process where amino acidsare assembled into polypeptides

1. mRNA leaves nucleus & attaches to a ribosome 2. The start codon (AUG) on mRNA allows its complementary anticodon on tRNA to move in3. A ribosome can hold another ‘codon-anticodon’ pairing so the two amino acids are linked by a peptide bond

4. Then ribosome slides down mRNA to ‘read’ next codon and repeats the process5. The polypeptide (a chain of amino acids) is complete when a stop codon is reached

I. Ribosomes• those that are free in cytoplasm

produce proteins that will be used within cell.

J. Endoplasmic reticulum (ER)• proteins that are

exported outside cell are produced by ribosomes attached

to the ER

See a video clip aboutPROTEIN SYNTHESIS

Video 4

TRANSLATION VIDEO (Choose Large video)

• DNA → DNA ____________The Central Dogma Of BiologyDNA RNA Proteins

• DNA → RNA ____________

• RNA→ Protein ___________

REPLICATION

TRANSCRIPTION

TRANSLATION

GENES & PROTEINSProteins are the connection

betweenthe gene code in the DNA and how

thatgene is expressed.

A gene that codes for an enzyme (protein) to make a pigment can control the color of a flower.

A gene that codes for an enzyme (protein) adds carbohydrates to glycoproteins to produce your blood type.

Enzymes catalyze and regulate chemical reactions so proteins build and operate all cell components.

Mendel/flower images from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.htmlBlood cell by Riedell