DNA,RNA&ProteinSynthesis2011

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DNA, RNA &

PROTEIN

SYNTHESIS

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DNA

and

Genes

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DNA or Protein?

1.

1. Walter Sutton discovered Walter Sutton discovered

chromosomes

chromosomes were made of DNA were made of DNA

and Protein

However, scientists were _{However, scientists were}NOT_NOT

sure which one (protein or DNA)

was

was the actual genetic material the actual genetic material

of the cell…

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4

It’s

DNA!

1b.

Frederick Griffith in 1928 showed Frederick Griffith in 1928 showed the

the DNA_DNA was the cell’s genetic was the cell’s genetic material

material

Watson & Crick in _{Watson & Crick in} the 1950’s built the

the 1950’s built the

1

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Structure of DNA

2a.

DNA is made of subunits

called

nucleotides

2b.

DNA nucleotides are

composed of 3 parts:

-

-*

*

Phosphate

*

Deoxyribose

Sugar

*

A Nitrogen-containing

A

Nitrogen-containing

Base (A, T, G, or C)

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Structure of DNA

3.

What is the structural

shape? (B4.2C.1)

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DNA Nucleotide

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Base Pairing Rule

• Watson and Crick showed that DNA is Watson and Crick showed that DNA is a

a double helixdouble helix

4a.

4a. The 4 bases in DNA are: _{The 4 bases in DNA are:} adenine adenine (A), (A), thymine (T),

thymine (T), guanine (G),guanine (G), and and cytosine (C)cytosine (C)

4b. The Base-Pairing Rule:

A

A (adenine) pairs with T (adenine) pairs with T (thymine) (thymine)

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5’ to 3’ Sugars

When the DNA double helix

When the DNA double helix

unwinds

unwinds, it resembles a _{, it resembles a}ladder_ladder

5.

The sides of the ladder are the The sides of the ladder are the

sugar & phosphate backbones

6.

6. The rungs of the ladder are the _{The rungs of the ladder are the} complementary paired bases

complementary paired bases

The two DNA strands are The two DNA strands are anti-parallel

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7. Sketch and label the basic structure of DNA.

( Anti-Parallel

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DNA

Replication

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Steps in DNA Replication

Occurs when chromosomes duplicate

Occurs when chromosomes duplicate

(make copies)

1.

1._{An exact copy of the DNA}_Anexact copy of the DNA is created _{is created}

with the aid of the enzyme

with the aid of the enzyme DNA DNA polymerase

polymerase

2.

2. Steps in the process: (B4.2g.2)_{Steps in the process: (B4.2g.2)}

a.a. Hydrogen Hydrogen bonds between bases are brokenbonds between bases are broken

b.

b. Enzymes “unzip” Enzymes “unzip” the molecule the molecule

c.

c. Each old strand of nucleotides serves as a Each old strand of nucleotides serves as a

template

template (model) (model) for each new strandfor each new strand

d.

d. New nucleotidesNew nucleotides move into complementary move into complementary positions and are joined together by

positions and are joined together by DNA DNA polymerase

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3.

Where does this all

happen? (B4.2g.1)

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4.

4. Two New, Two New,

Identical DNA

Strands

Strands Result Result from

from

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Another View of Replication

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RNA

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RNA Differs from DNA

1.

1. RNARNA has a sugar ribose has a sugar ribose

DNADNA has a sugar deoxyribose – missing_{has a sugar}deoxyribose – missing

oxygen.

2.

2. RNARNA contains the base uracil (U) contains the base uracil (U)

DNADNA has thymine (T) has thymine (T)

3.

3. RNA molecule is single-stranded RNA molecule is single-stranded

DNA is

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Structure of RNA

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.

5.

Three Types of RNA

1.

1. Messenger RNA (mRNA)Messenger RNA (mRNA)

2.

2. Ribosomal RNA (rRNA)Ribosomal RNA (rRNA)

3.

3. Transfer RNA (tRNA)Transfer RNA (tRNA)

*** They each have a slightly

different job…

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.

Three Types of RNA, cont’d…

6.

6. Messenger RNA (mRNA) copies Messenger RNA (mRNA) copies

DNA’s code & carries the genetic

information to the ribosomes

7.

7. Ribosomal RNA (rRNA), along _{Ribosomal RNA (rRNA), along}

with protein,

with protein, makes up the makes up the

ribosomes – site of protein

synthesis

synthesis (makes protein)_{(makes protein)} 8.

8. Transfer RNA (tRNA) transfers Transfer RNA (tRNA) transfers

amino acids to the ribosomes

where proteins are synthesized

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Base-Pairing & mRNA

9. What bases pair together on RNA?

A <–> U & C <–> G.

• mRNA is a Long Straight

chain of Nucleotides

• 6b. mRNA is made in the Nucleus

• 6c. mRNA Copies DNA & leaves through nuclear pores

• mRNA Contains the

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Fun Facts on Ribosomal RNA

(rRNA)

• Globular in shape_{Globular in shape}

• Made inside the nucleus Made inside the nucleus of a cell

of a cell

• Associates with proteins _{Associates with proteins}

to form ribosomes

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Fun Facts on Transfer RNA

(tRNA)

• Clover-leaf shape

• Single stranded molecule with attachment site at one end for an amino acid

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Protein Synthesis (Making a

Protein)

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Genes & Proteins

1.

Proteins are made of chains

of

of amino acids

amino acids

linked together

by

by peptide bonds

peptide bonds

2.

20

different amino acids

exist



Amino acids chains are called

polypeptides (a.k.a. protein)

3.

Genes are segments of DNA

Genes are

segments of DNA

that code for the amino acid

sequence in a protein…

Example: AAT GCG codes for 2 different amino acids (these are

Example: AAT GCG codes for 2 different amino acids (these are

like nuclear directions on how to make the protein)

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The Roles of RNA and

DNA

4. DNA contains the master code (idea) for making proteins

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DNA Begins the Process…

6.

DNA is found in the nucleus of a cell and begins the process of making a protein

7. Proteins, however, are made in the cytoplasm of cells by

organelles called ribosomes 8. Ribosomes may be

1.free floating in the cytoplasm or

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Starting with DNA

9.

The 1

stst

step in making a

protein is to make a copy of

DNA ‘s code

in the nucleus.

That code is then taken out

to the cytoplasm

10.

What happens in the

cytoplasm?

the code must be read (de-the code must be read

(de-coded) so that amino acids can be assembled to make

coded) so that amino acids can be assembled to make

polypeptides (proteins)

– This process is called PROTEIN This process is called PROTEIN

SYNTHESIS

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11.

The Pathway to Making a

Protein

(PROTEIN SYNTHESIS)(PROTEIN SYNTHESIS)

DNA

mRNA

tRNA (ribosomes)

Protein

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DNA



RNA



Protein

Nuclear membrane

Transcription Transcription

RNA Processing

Translation Translation

DNA

Pre-mRNA

mRNA

Ribosome

Protein

Eukaryotic

Cell

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Protein Synthesis

12.

12. Definition: Definition: The production of

polypeptide chains (a.k.a. proteins) from the code of DNA

13. Two phases of protein synthesis:

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Transcription and

Translation

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The Two Phases of

Protein Synthesis

†

TranscriptionTranscription: makes an RNA : makes an RNA

molecule complementary to a portion molecule complementary to a portion

of DNA of DNA

†(DNA -> mRNA)(DNA -> mRNA)

†

TranslationTranslation: occurs when the : occurs when the sequence of bases of mRNA sequence of bases of mRNA

DIRECTS the sequence of amino DIRECTS the sequence of amino

acids in a polypeptide acids in a polypeptide

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The Genetic Code

1.

1. DNA contains a triplet DNA contains a triplet code. Every three code. Every three bases on DNA stands for

bases on DNA stands for ONE amino acid. ONE amino acid.

Example: ATG = 1 triplet code of DNA

Example: ATG = 1 triplet code of DNA 2.

2. A codon is a three-letter unit on mRNA, A codon is a three-letter unit on mRNA, complementing the DNA

complementing the DNA

Example: If DNA reads ATG, then the

Example: If DNA reads ATG, then the

complementary mRNA would be UAC… UAC is a codon)

complementary mRNA would be UAC… UAC is a codon) 3.

3. Each Each codoncodon stands for stands for an amino acidan amino acid

Example: UAC stands for the amino acid

Tyrosine

Tyrosine 4.

4. MostMost amino acids amino acids have more than one codonhave more than one codon!! 5.

5. There are 20 There are 20 amino acids and 64 amino acids and 64 possible possible different triplets

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Remember the

Complementary Bases

6.

6. On DNA:

A-T and C-G

Example: Given TAG CAT, the DNA complement would be ATC GTA

(used when DNA replicates)

7.

7. On RNA:

A-U and C-G

Example: Given TAG CAT, the mRNA complement would be AUC GUA

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The Genetic Code

8. Use the code by

reading

from the center to the outside

•Example: AUG codes for

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38 Name the Amino Acids

(you may have an iPad App for more practice with this too…)

•

GGG?

•

UCA?

•

CAU?

•

GCA?

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9.

Name the Amino Acids

• GGG - Glycine

• UCA - Serine

• CAU - Histidine

• GCA - Alanine

• AAA – Lysine

AUG is the “start” codon (Methionine is a chemical signal to start)

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Transcription

10.

Definition:

The process of

copying the sequence of one

strand of DNA, the template

strand. It occurs in the

nucleus.

11.

mRNA

copies the template

strand of DNA

12.

Are both strands copied?

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An overview of what happens

during Transcription…

• During transcription:

1.RNA polymerase (enzyme) binds to DNA and separates the DNA strands

2.RNA Polymerase then uses one

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Question:

13.

What would be the

complementary RNA strand

for the following DNA

sequence?

DNA =

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Answer:

13.

•

DNA GCGTATG

•

RNA CGCA

U

AC

*** notice that U replaces T

in RNA

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mRNA Transcription

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Translation

(i.e de-coding the code)

Synthesis of proteins in the

Synthesis of proteins in the

cytoplasm…

15.

15. Translation involves the _{Translation involves the}

following 4 things:

1.

1. mRNA (codons)_{mRNA (codons)}

2.

2. tRNA (anticodons)tRNA (anticodons)

3.

3. RibosomesRibosomes

4.

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Translation

16.

Definition:

the process of

decoding the mRNA into an

amino acid chain (a.k.a

protein). It occurs in the

cytoplasm of the cell.

17.

Ribosomes read mRNA

three bases, or 1 codon, at a

time

and construct the

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Transcription

Transcription

Translation

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On and Off…

18.

18. Methionine is called the start codon Methionine is called the start codon & is & is represented by

represented by AUGAUG

* this code tells the ribosome to begin protein * this code tells the ribosome to begin protein

assembly assembly

19.

19. UAA, UAG, or UGA UAA, UAG, or UGA – stop codons – stop codons

* these codes tell the ribosome to stop protein

assembly

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Messenger RNA

(mRNA)

methionine glycine serine isoleucine glycine alanine stop codon

protein

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

mRNA

start codon

Primary structure of a protein

aa1 aa2 aa3 aa4 aa5 aa6

peptide bonds

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Transfer RNA (tRNA)

Made up of 75 to 80 nucleotidesMade up of 75 to 80 nucleotides long long

• 20.20. tRNA picks up the appropriate amino acid, tRNA picks up the appropriate amino acid,

which attaches to one end of the tRNA molecule

for transport, found floating in the cytoplasm

• 21.21. Opposite the attachment site on tRNA are 3 Opposite the attachment site on tRNA are 3 nucleotide bases called the

nucleotide bases called the anticodonanticodon..

• 22.22. A codon on mRNA is complementary to an A codon on mRNA is complementary to an

anticodon

anticodon on tRNA (this is how they know to on tRNA (this is how they know to match up

match up 

– tRNA recognizes the appropriate codons on the mRNA and bonds to them with tRNA recognizes the appropriate codons on the mRNA and bonds to them with

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Codons and Anticodons

• The 3 bases of an

anticodon are

complementary to the 3 bases of a codon

23. Example:

Codon ACU

The complementary

Anticodon is UGA

UGA

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24.

Make a sketch of this

molecule (tRNA)

amino acid

amino acid

attachment site

U A C

Anticodon

methionine

Amino Acid

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Translation

•

Three steps:

25.

1.

1. initiationinitiation: start codon (AUG): start codon (AUG) 2.

2. elongation_elongation: amino acids linked_{: amino acids linked}

3.

3. termination_termination: stop _{: stop}codon codon (UAG, (UAG, UAA, or UGA).

UAA, or UGA).

Let’s Make a Protein !

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Step 1- Initiation

26.

mRNA transcript mRNA transcript

start codon AUG

start codon AUG

attaches to the small

ribosomal subunit

27.

What happens

next?

The mRNA & The mRNA & Small subunit attach

Small subunit attach

to the large ribosomal

subunit

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28.

Ribosomes

P

Site

A

Site

Large subunit

Small subunit

mRNA

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Step 2 - Elongation

29. The Ribosome moves along the mRNA strand one codon at a time

30. Two tRNA, with their amino acids, fit & move into site A and P of the ribosome

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Initiation – Step 1

mRNA

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

2-tRNA

G

aa2

A U

A

1-tRNA

U A C aa1

anticodon

hydrogen

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60 mRNA

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

1-tRNA 2-tRNA

U A C G

aa1 _aa2

A U

A

anticodon

hydrogen

bonds _codon

32. peptide bond

3-tRNA

G A A aa3

32.

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61 mRNA

1-tRNA

2-tRNA

U A C

G aa1 aa2 A U A peptide bond 3-tRNA

G A A aa3

Ribosomes move over one codon at a time

33. tRNA leaves

attachment site

to get another

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62 mRNA

2-tRNA

G aa1

aa2

A U

A peptide bonds

3-tRNA

G A A aa3

4-tRNA

G C U aa4

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63 mRNA

2-tRNA

G

aa1

aa2

A U

A peptide bonds

3-tRNA

G A A aa3

4-tRNA

G C U aa4

A C U

(leaves)

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mRNA G C U A C U U C G

aa1

aa2

A peptide bonds

3-tRNA

G A A aa3

4-tRNA

G C U aa4

A C U

U G A

5-tRNA

aa5

34. When a tRNA leaves the ribosome, the

ribosome moves down the mRNA strand allowing

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65 mRNA

mRNA G C U A C U U C G

aa1

aa2

A peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U aa4

A C U

U G A

5-tRNA

aa5

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66 mRNA

mRNA

A C A U G U

aa1 aa2 U primary primary structure structure

of a protein

aa3

200-tRNA

aa4

U A G aa5 C U aa200 aa199 terminator terminator

or stopor stop

codoncodon 36.

36. Termination_Termination -

-Last stage of

Last stage of

translation

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37.

End Product –The Protein!

• The end products of protein

synthesis is a primary structure of a protein

• A sequence of amino acid bonded together by peptide bonds

aa1

aa2 aa3 aa4

aa5