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PROTEIN SYNTHESIS. DNA and Genes. DNA contains genes , sequences of nucleotide bases These Genes code for polypeptides (proteins) Proteins are used to build cells and do much of the work inside cells. DNA. Proteins are made of amino acids linked together by peptide bonds

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Presentation Transcript
slide3

DNA contains genes, sequences of nucleotide bases

These Genes code for polypeptides (proteins)

Proteins are used to build cells and do much of the work inside cells

DNA
polypeptides
Polypeptides
  • Amino acid chains are called polypeptides
dna begins the process

DNA is found inside the nucleus

Proteins, however, are made in the cytosol of cells by organelles called ribosomes

Ribosomes may be free in the cytosol or attached to the surface of rough ER

DNA Begins the Process
starting with dna

DNA ‘s code must be copied and taken to the cytosol

  • In the cytosol, this code must be read so amino acids can be assembled to make polypeptides (proteins)
  • This process is called PROTEIN SYNTHESIS
Starting with DNA
roles of rna and dna

DNA is the MASTER PLAN

RNA is the BLUEPRINT of the Master Plan

Roles of RNA and DNA
rna differs from dna

RNA has a sugar ribose

DNA has a sugar deoxyribose

RNA Differs from DNA
other differences

RNA contains the base uracil (U)

DNA has thymine (T)

  • RNA molecule is single-stranded

DNA is double-stranded

Other Differences

DNA

three types of rna

Messenger RNA (mRNA) copies DNA’s code & carries the genetic information to the ribosomes

  • Ribosomal RNA (rRNA), along with protein, makes up the ribosomes
  • Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized

.

Three Types of RNA
messenger rna

Long Straight chain of Nucleotides

Made in the Nucleus

Copies DNA & leaves through nuclear pores

Contains the Nitrogen Bases A, G, C, U ( no T )

Messenger RNA
messenger rna mrna

Carries the information for a specific protein

  • Made up of 500 to 1000 nucleotides long
  • Sequence of 3 bases called codon
  • AUG – methionine or start codon
  • UAA, UAG, or UGA – stop codons
Messenger RNA (mRNA)
ribosomal rna rrna

rRNA is a single strand 100 to 3000 nucleotides long

  • Globular in shape
  • Made inside the nucleus of a cell
  • Associates with proteins to form ribosomes
  • Site of protein Synthesis
Ribosomal RNA (rRNA)
the genetic code

A codon designates an amino acid

An amino acid may have more than one codon

There are 20 amino acids, but 64 possible codons

Some codons tell the ribosome to stop translating

The Genetic Code
the genetic code1
The Genetic Code
  • Use the code by reading from the center to the outside
  • Example: AUG codes for Methionine
name the amino acids

GGG?

UCA?

CAU?

GCA?

AAA?

Name the Amino Acids
transfer rna trna

Clover-leaf shape

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

Opposite end has three nucleotide bases called the anticodon

Transfer RNA (tRNA)
transfer rna

amino acid

attachment site

U

A

C

anticodon

Transfer RNA
codons and anticodons
Codons and Anticodons
  • The 3 bases of an anticodon are complementary to the 3 bases of a codon
  • Example: Codon ACU

Anticodon UGA

UGA

ACU

pathway to making a protein

DNA

mRNA

tRNA (ribosomes)

Protein

Pathway to Making a Protein
protein synthesis1

The production or synthesis of polypeptide chains (proteins)

  • Two phases:Transcription & Translation
  • mRNA must be processed before it leaves the nucleus of eukaryotic cells
Protein Synthesis
dna rna protein

Nuclear

membrane

DNA

Transcription

Pre-mRNA

RNA Processing

mRNA

Ribosome

Translation

Protein

DNA RNAProtein

Eukaryotic Cell

transcription

The process of copying the sequence of one strand of DNA, the template strand

  • mRNA copies the template strand
  • Requires the enzyme RNA Polymerase
Transcription
answer

DNA 5’-GCGTATG-3’

  • RNA 3’-CGCAUAC-5’
Answer:
transcription1

During transcription, RNA polymerase binds to DNA and separates the DNA strands

RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA

Transcription
transcription2

Promoters are regions on DNA that show where RNA Polymerase must bind to begin the Transcription of RNA

  • Called the TATA box
  • Specific base sequences act as signals to stop
  • Called the termination signal
Transcription
mrna processing

After the DNA is transcribed into RNA, editing must be done to the nucleotide chain to make the RNA functional

  • Introns, non-functional segments of DNA are snipped out of the chain
mRNA Processing
mrna editing

Exons, segments of DNA that code for proteins, are then rejoined by the enzyme ligase

  • A guanine triphosphate cap is added to the 5” end of the newly copied mRNA
  • A poly A tail is added to the 3’ end of the RNA
  • The newly processed mRNA can then leave the nucleus
mRNA Editing
slide38

Result of Transcription

New Transcript

Tail

CAP

mrna transcript
mRNA Transcript
  • mRNA leaves the nucleus through its pores and goes to the ribosomes
translation

Translation is the process of decoding the mRNA into a polypeptide chain

Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins

Translation
slide41

Transcription

Translation

ribosomes

Made of a large and small subunit

Composed of rRNA (40%) and proteins (60%)

Have two sites for tRNA attachment --- P and A

Ribosomes
step 1 initiation

mRNA transcript start codon AUG attaches to the small ribosomal subunit

Small subunit attaches to large ribosomal subunit

Step 1- Initiation

mRNA transcript

ribosomes1

mRNA

A

U

G

C

U

A

C

U

U

C

G

Ribosomes

Large

subunit

P

Site

A

Site

Small subunit

step 2 elongation
Step 2 - Elongation
  • As ribosome moves, two tRNA with their amino acids move into site A and P of the ribosome
  • Peptide bonds join the amino acids
initiation

aa2

aa1

2-tRNA

1-tRNA

G

A

U

U

A

C

Initiation

anticodon

A

U

G

C

U

A

C

U

U

C

G

A

hydrogen

bonds

codon

mRNA

slide47

aa3

3-tRNA

G

A

A

Elongation

peptide bond

aa1

aa2

1-tRNA

2-tRNA

anticodon

U

A

C

G

A

U

A

U

G

C

U

A

C

U

U

C

G

A

hydrogen

bonds

codon

mRNA

slide48

aa3

3-tRNA

G

A

A

aa1

peptide bond

aa2

1-tRNA

U

A

C

(leaves)

2-tRNA

G

A

U

A

U

G

C

U

A

C

U

U

C

G

A

mRNA

Ribosomes move over one codon

slide49

aa4

4-tRNA

G

C

U

peptide bonds

aa1

aa2

aa3

2-tRNA

3-tRNA

G

A

U

G

A

A

A

U

G

C

U

A

C

U

U

C

G

A

A

C

U

mRNA

slide50

aa4

4-tRNA

G

C

U

peptide bonds

aa1

aa2

aa3

2-tRNA

G

A

U

(leaves)

3-tRNA

G

A

A

A

U

G

C

U

A

C

U

U

C

G

A

A

C

U

mRNA

Ribosomes move over one codon

slide51

aa5

5-tRNA

U

G

A

peptide bonds

aa1

aa2

aa4

aa3

3-tRNA

4-tRNA

G

A

A

G

C

U

G

C

U

A

C

U

U

C

G

A

A

C

U

mRNA

slide52

aa5

5-tRNA

U

G

A

peptide bonds

aa1

aa2

aa3

aa4

3-tRNA

G

A

A

4-tRNA

G

C

U

G

C

U

A

C

U

U

C

G

A

A

C

U

mRNA

Ribosomes move over one codon

slide53

aa5

aa4

Termination

aa199

aa200

aa3

primary

structure

of a protein

aa2

aa1

terminator

or stop

codon

200-tRNA

A

C

U

C

A

U

G

U

U

U

A

G

mRNA

end product the protein

aa5

aa4

aa3

aa2

aa199

aa1

aa200

The end products of protein synthesis is a primary structure of a protein

A sequence of amino acid bonded together by peptide bonds

End Product –The Protein!
messenger rna mrna1

start

codon

A

U

G

G

G

C

U

C

C

A

U

C

G

G

C

G

C

A

U

A

A

mRNA

codon 1

codon 2

codon 3

codon 4

codon 5

codon 6

codon 7

stop

codon

protein

methionine

glycine

serine

isoleucine

glycine

alanine

Primary structure of a protein

aa2

aa3

aa4

aa5

aa6

aa1

peptide bonds

Messenger RNA (mRNA)