DNA, RNA & Protein Synthesis

I. What are Proteins?

A. Proteins are organic molecules made of various arrangements of 20 amino acids

B. Examples-1. Enzymes.2. Transport proteins and receptor

molecules in cell membranes-ex. hemoglobin

…

3. Hormones- ex. Insulin, adrenaline, testosterone

4. Structural proteins- ex. Keratin and collagen in skin, actin and myosin of muscle.

I. What are Proteins? (con’t)

…

5. Antibodies

6. Storage molecules- ex. Albumin in egg white, casein in milk, and plant proteins in seeds.

I. What are Proteins? (con’t)

• Amino Acids are put together at the ribosome to Amino Acids are put together at the ribosome to form proteins…form proteins…

• The order in which the amino acids are to be The order in which the amino acids are to be arranged depends on the instructions from your arranged depends on the instructions from your genes …genes …

which can be found in the “control center”…which can be found in the “control center”…

the nucleus…the nucleus…

……which contains DNA…which contains DNA…

……where your genes are foundwhere your genes are found

II. How are proteins made? II. How are proteins made?

III. What is a Gene?

A gene is a length of DNA that codes for a protein (or one subunit in a protein.)

IV. What is DNA?

Deoxyribonucleic Acid

A. DNA Structure

1. The structure of DNA was first described by Watson & Crick in 1953.

• Double helix- twisted ladder       

A. DNA Structure

      

2.The DNA molecule is made up of Nucleotides.

B. A Nucleotide – the building blocks of DNA1. Sugar

2. Phosphate group (phosphoric acid)3. A Nitrogen base

So for DNA…the sugar = deoxyribosephosphate groupnitrogen base (4 different kinds)

AdenineThymineCytosineGuanine

C. Shape of DNA-twisted ladder

1. Sides of the ladder= sugar + phosphate

2. Rungs (steps) = nitrogen bases

PP

PP

S

S

S

S

S

S

NB

NB

NB

C. Shape of DNA-twisted ladder(con’t)

3. sugar + phosphate are held together by strong covalent bonds

4. nitrogen bases are held together by weak hydrogen bonds

PP

PP

S

S

S

S

S

S

NB

NB

NB

D. The Nitrogenous Bases1. 4 nitrogenous bases of DNA

a. Adenineb. Thyminec. Cytosined. Guanine

2. Base-Pairing Rule:Adenine pairs with Thymine (A-T, T-A)Guanine pairs with Cytosine (C-G, G-C)

E. DNA’s Problem

1. DNA cannot leave the nucleus.2. So, How does it get the instructions to

the ribosome?....… RNA

V. What is RNA?

Ribonucleic Acid

A. RNA Structure

1. RNA is made up of nucleotides.

a. Sugar = Ribose

b. Phosphate Group

c. 4 Different Nitrogen Bases

1. Adenine

2. Uracil

3. Cytosine

4. Guanine

A. RNA Structure

2. Base-Pairing Rule-

Adenine pairs with Uracil

Cytosine pairs with Guanine

3. RNA is single-stranded.

4. RNA can leave the nucleus.

B. Types of RNA

1. mRNA- messenger RNA takes DNA’s instruction from the nucleus to the ribosome.

2. tRNA- transfer RNA brings an amino acid from the cytoplasm to the ribosome.

3. rRNA- ribosomal RNA

C. Going from DNA to mRNA to tRNA

(one side)DNA strand…

…pairs withmRNA strand…

…pairs with

tRNA strand

A U A

T A U

C G C

G C G

VI. How does DNA give the message to RNA? Transcription

A. Transcription is the process of DNA making RNA.

1. The DNA strands separate at the H-bonds holding the nitrogen bases together. *An enzyme causes the unwinding.

B. Steps of Transcription:DNA strand

The Nucleus

deoxyribose

phosphate

adenine

thymine

cytosineguanine

ribose

uracil

2. mRNA (messenger RNA) pairs up with DNA

B. Steps of Transcription:DNA strand

The Nucleus

deoxyribose

phosphate

adenine

thymine

cytosineguanine

ribose

uracil

3. The mRNA nucleotides covalently bond.

B. Steps of Transcription:DNA strand

The Nucleus

deoxyribose

phosphate

adenine

thymine

cytosineguanine

ribose

uracil

4. The DNA strands will bond back together.

5. The mRNA chain can now leave the nucleus & goes to Ribosome.

B. Steps of Transcription:DNA strand

The Nucleus

deoxyribose

phosphate

adenine

thymine

cytosineguanine

ribose

uracil

6. Where is mRNA going? ………………………………to a ribosome

B. Steps of Transcription:DNA strand

The Nucleus

deoxyribose

phosphate

adenine

thymine

cytosineguanine

ribose

uracil

VII. What Happens at the Ribosome? Translation

A. Translation is protein synthesis and occurs on a ribosome.

B. The ribosome is a protein-RNA structure with two binding sites for a mRNA molecule. It will read 2 codons at a time.

* A codon is 3 nucleotides of mRNA.

nucleus

ribosome

codon

mR

NA

mRNAcodoncodoncodon

AA AU

U

U U UC C C

G G

cytoplasm

C. Steps of Translation

1. First mRNA binds to the ribosome at the “START” codon (AUG) of mRNA.

2. A tRNA (transfer RNA) molecule with an anticodon at one end and an amino acid at the other binds to the first codon of mRNA.

* an anticodon is 3 nucleotides of tRNA

*Thank you to Lew-Ports Biology Place !

nucleus

ribosome

codon

mR

NA

mRNA

tRNA

anticodon

codoncodoncodon

A

A

A

A

AU U U U

U

C C C

C

G

G

G

cytoplasm

START

3. The second tRNA binds to the second codon of mRNA.

4. The first two amino acids bond.

C. Steps of Translation

nucleus

ribosome

codon

mR

NA

mRNA

tRNA tRNA

anticodon

codoncodoncodon

A

A

A AU U U U

G

C C C

G

G G

cytoplasm

proline START

nucleus

ribosome

codon

mR

NA

mRNA

tRNA

anticodon

codoncodoncodon

AA

A

AU

U

U U UC

C

C CG G

cytoplasm

prolinevaline START

5. This process continues until a “STOP” codon is read by the ribosome;

6. An amino acid chain is the result…

C. Steps of Translation

nucleus

ribosome

codon

mR

NA

mRNA

tRNA

anticodonanticodon

codoncodoncodon

AA

A A

A

U

U U U UC C C

G

G

G

cytoplasm

prolinevalineleucine START

cytoplasm

D. Result of Translation

1. Proteins are the result of translation

2. 3D shape from ER.

3. It can then be used in the cell or released from the cell into the organism.

• DNA Workshop Activity