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BELLRINGER:. Draw the following box and fill in the squares:. REPLICATION. TRANSCRIPTION. Where in the cell does this take place?. Where in the cell does this take place?. What is created in this process?. What is created in this process?. WHY does this take place?.

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Bellringer

BELLRINGER:

Draw the following box and fill in the squares:

REPLICATION

TRANSCRIPTION

Where in the cell does this take place?

Where in the cell does this take place?

What is created in this process?

What is created in this process?

WHY does this take place?

WHY does this take place?


The three types of rna

THE THREE TYPES OF RNA


Section 11 2 summary pages 288 295

  • There are three types of RNA that help build proteins.

Section 11.2 Summary – pages 288 - 295

# 1 Messenger RNA (mRNA) brings instructions from DNA in the nucleus to the cytoplasm.

Then mRNA binds to ribosomes.


Section 11 2 summary pages 288 2951

Section 11.2 Summary – pages 288 - 295

# 2 Transfer RNA (tRNA) is the supplier.

Transfer RNA delivers amino acids (the building blocks of proteins) to the ribosome to be assembled into a protein.

Amino Acid

How it binds with mRNA


Section 11 2 summary pages 288 2952

# 3 Ribosomes are made of Ribosomal RNA (rRNA).

Section 11.2 Summary – pages 288 - 295

rRNA uses the instructions from mRNA and the supplies from tRNA to assemble the amino acids in the correct order.


Bellringer

  • mRNA brings the instructions.

  • tRNA supplies the amino acid parts.

  • rRNA builds the proteins using the instructions and amino acids.

RIBOSOME


The process of translation

THE PROCESS OF TRANSLATION


Protein synthesis

Protein Synthesis

Transcription

Translation


Section 11 2 summary pages 288 2953

Why does mRNA have to be made?

(Why can’t DNA deliver it’s own instructions)

Section 11.2 Summary – pages 288 - 295

Nucleus


Section 11 2 summary pages 288 2954

The Genetic Code

Section 11.2 Summary – pages 288 - 295

  • Every three letters on a mRNA strand, called a codon, is a code for a specific amino acid (a building block to make protein)


Bellringer

Every three letters on an mRNA strand is a codon.

Each codon codes for a specific amino acid.

CODON CHART

Things to notice:

There are 64 possible codon combinations

There are only 20 different amino acids

Most amino acids correspond to more than one codon


Translation

Translation

changingnucleic acid languagetoamino acid language


Section 11 2 summary pages 288 2955

Step 1:

Section 11.2 Summary – pages 288 - 295

  • As translation begins, the “capped” end of mRNA strand attaches to a ribosome.

mRNA strand

Ribosome


Section 11 2 summary pages 288 2956

tRNA’s role

Section 11.2 Summary – pages 288 - 295

  • tRNAs bring amino acids to the ribosomes.

mRNA

Coming from Nucleus

RIBOSOME


Bellringer

  • Each tRNA only carries one amino acid.

Amino acid


Section 11 2 summary pages 288 2957

  • There are also three nucleotides on the bottom of the tRNA called an anti-codon.

  • Anti-codons complementary base pair with the codons on mRNA.

    (this is to make sure they are bringing the correct amino acid- If the anti-codon doesn’t base pair with the codon, then the wrong amino acid was brought)

Section 11.2 Summary – pages 288 - 295

Anti-codon


Section 11 2 summary pages 288 2958

Step 2: Initiation

  • AUG is usually the first codon on the mRNA strand.

  • This signals the ribosome to START making a protein.

Section 11.2 Summary – pages 288 - 295

Methionine

  • The initiator tRNA with anticodon UAC comes and binds with this codon and drops off it’s amino acid “Methionine”.


Section 11 2 summary pages 288 2959

  • After the first tRNA binds with its codon, the mRNA slides down so that the ribosome can read the next codon.

Section 11.2 Summary – pages 288 - 295


Section 11 2 summary pages 288 29510

  • A new tRNA molecule carrying an amino acid pairs with the second mRNA codon.

Section 11.2 Summary – pages 288 - 295

Alanine


Section 11 2 summary pages 288 29511

  • The amino acids then bond together. What kind of bond is it?

  • Once the first tRNA lets go of it’s amino acid, it is released from the ribosome.

Section 11.2 Summary – pages 288- 295

PEPTIDE BOND

Methionine

Alanine

bond


Section 11 2 summary pages 288 29512

Step 3: Elongation

  • Refers to the time that the amino acid chain (poly-peptide) is being built or “elongated”.

Section 11.2 Summary – pages 288- 295


Section 11 2 summary pages 288 29513

Step 4: Termination

  • A chain of amino acids is formed until the stop codon is reached on the mRNA strand.

Section 11.2 Summary – pages 288 - 295

The end result is a protein

Stop codon


Ribosomes

Ribosomes

  • A site (aminoacyl-tRNA site)

    • holds tRNA carrying next amino acid to be added to chain

  • P site (peptidyl-tRNA site)

    • holds tRNA carrying growing polypeptide chain

  • E site (exit site)

    • empty tRNA leaves

      ribosome from exit site

Met

C

A

U

5'

G

U

A

3'

E

P

A


Bellringer

The Wobble Effect

Look at your codon chart and find an example of different codons that code for the same amino acid.

For codon-anticodon interactions, the third base of the codon isn’t read as “strictly” in the DNA/mRNA sequence during transcription or DNA replication.

CUU; CUC; CUA

This is called the wobble effect.

As long as the first two bases are the same, the last base doesn’t matter all that much. Each of these mRNA codon sequences will bond with a single type of tRNA that carries leucine.


Prokaryote vs eukaryote genes

Prokaryotes

DNA in cytoplasm

circular chromosome

naked DNA

no introns

Eukaryotes

DNA in nucleus

linear chromosomes

DNA wound on histone proteins

introns vs. exons

intron = noncoding (inbetween) sequence

exon = coding (expressed) sequence

Prokaryote vs. Eukaryote genes

eukaryotic

DNA


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