Think, Pair, Share What do you already know about DNA?

DNA Structure Deoxyribo Nucleic Acid One molecule of DNA, consists of
2 strands of repeating units called nucleotides The 2 strands are twisted into a double helix

DNA: The monomers Deoxyribonucleic acid
Made up of lots of nucleotides joined together. Phosphate A nitrogenous base Ribose sugar (RNA) Deoxyribose sugar (DNA)

DNA: The bases There are 4 different bases Guanine Cytosine Adenine
Thymine Adenine and Guanine are Purine bases. Cytosine, Thymine and Uracil are Pyramidine bases.

DNA: The sugar phosphate backbone
DNA is a polymer of mononucleotides. Mononucleotides join together between the phosphate of one nucleotide and the phosphate group of the adjoining nucleotide. Really strong bond

DNA: A polynucleotide The sugar and phosphate units make up the “backbone” of the nucleic acid. one nucleotide A base is attached to each sugar molecule.

DNA: Base pairing The two strands of the double helix are held together by hydrogen bonds between the bases. Hydrogen bonds are singularly very weak but collectively can be very strong.

DNA: Complementary base pairing
Adenine pairs with Thymine Guanine pairs with Cytosine A and T are complimentary base pairs. C and G are complimentary base pairs.

Double helix structure of DNA

3D model of DNA double helix

What is the function of DNA
Heredity material responsible for passing genetic information from cell to cell. How is it adapted to do its job? Stable 2 strands can separate so it can self-replicate. Large molecule that carries LOTS of information Base pairing prevents corruption from outside chemicals or physical forces.

Protein synthesis: Transcription
Learning Intentions Identify the differences between RNA and DNA Describe the process of Transcription

What is the function of DNA?
The function of DNA is to code for proteins. Not all of the DNA molecule codes for proteins. The functional part of DNA that can is known as a Gene

RNA Genes are instructions to build a protein.
Unfortunately the DNA that contains the genes can’t leave the nucleus. So a copy of the gene must be made. This copy is known as Messenger RNA or mRNA. RNA is another type of nucleic acid

RNA Ribo nucleic acid Structurally different in 3 ways from DNA.
What are the differences?

Transcription Transcription is the name of the process in which a copy of DNA is made. The copy is known as messenger RNA This process occurs in the nucleus of the cell

A T T T T A T C G C C C T G C T A G C T G G G C A T
A section of the DNA in the nucleus is first unwound…. using DNA Helicase A T T T T A T C G C C C T G C T A G C T G G G C A T T A A A A T A G C G G G A C G A T C G A C C C G T A

The weak hydrogen bonds between the bases are broken….. A T T T T A T C G C C C T G C T A G C T G G G C A T T A A A A T A G C G G G A C G A T C G A C C C G T A

This causes part of the two strands of DNA to separate. A T T T T A T C G C C C T G C T A G C T G G G C A T T A A A A T A G C G G G A C G A T C G A C C C G T A

A T T T T A T C G C C C T G C T A G C T G G G C A T U
Free RNA nucleotides in the nucleoplasm find their complementary base pair on the DNA……. A T T T T A T C G C C C T G C T A G C T G G G C A T U T A A A A T A G C G G G A C G A T C G A C C C G T A

A T T T T A T C G C C C T G C T A G C T G G G C A T U A
Free RNA nucleotides in the nucleoplasm find their complementary base pair on the DNA……. A T T T T A T C G C C C T G C T A G C T G G G C A T U A T A A A A T A G C G G G A C G A T C G A C C C G T A

A T T T T A T C G C C C T G C T A G C T G G G C A T U A A
Free RNA nucleotides in the nucleoplasm find their complementary base pair on the DNA……. A T T T T A T C G C C C T G C T A G C T G G G C A T U A A T A A A A T A G C G G G A C G A T C G A C C C G T A

A T T T T A T C G C C C T G C T A G C T G G G C A T U A A A A
A hydrogen bond forms between the RNA nuclotide base and the complementary base on the DNA. A T T T T A T C G C C C T G C T A G C T G G G C A T U A A A A T A A A A T A G C G G G A C G A T C G A C C C G T A

A T T T T A T C G C C C T G C T A G C T G G G C A T U A A A A U
A hydrogen bond forms between the RNA nuclotide base and the complementary base on the DNA. A T T T T A T C G C C C T G C T A G C T G G G C A T U A A A A U T A A A A T A G C G G G A C G A T C G A C C C G T A

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

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

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

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

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

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

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

A T T T T A T C G C C C T G C T A G C T G G G C A T U A A A A U A G C
T A A A A T A G C G G G A C G A T C G A C C C G T A The enzyme RNA polymerase then catalyses the formation of the strong chemical bonds (phosphodiester) between the ribose sugar and phosphate groups of adjoining RNA nucleotides.

T A A A A T A G C G G G A C G A T C G A C C C G T A The enzyme RNA polymerase then catalyses the formation of the strong chemical bond between the ribose sugar and phosphate groups of adjoining RNA nucleotides.

T A A A A T A G C G G G A C G A T C G A C C C G T A The messenger RNA molecule is formed

U A A A A U A G C G G G A C G A U C G A C C C G U A T A A A A T A G C G G G A C G A T C G A C C C G T A Hydrogen bonds between the bases on mRNA and the bases on DNA break….

U A A A A U A G C G G G A C G A U C G A C C C G U A T A A A A T A G C G G G A C G A T C G A C C C G T A …….The mRNA is ready to make it’s journey out of the nucleus and into the cytoplasm.

T A A A A T A G C G G G A C G A T C G A C C C G T A The hydrogen bonds between the complementary bases on DNA re-form and the DNA is wound back into a helix again.

Tasks 1. Complete the diagram to show the complementary base pairing on mRNA 2. Add the following labels to your transcription diagram: Messenger RNA Nuclear pore Messenger RNA leaving the nucleus DNA strand 3. Cut and Stick the transcription description

Protein Synthesis: Translation
Learning Intentions Describe how mRNA gets translated into a protein.

Translation Translation is the process in which the mRNA is ‘read’ and translated into a protein. Translation occurs on the ribosomes The process involves another type of RNA molecule known as Transfer RNA or tRNA

U U U C G A U G C A U C G C A A C U C G C
The mRNA leaves the nucleus through a nuclear pore and enters the cytoplasm U U U C G A U G C A U C G C A A C U C G C Shows the exit of the mRNA from the nucleus

Shows how a ribosome binds to the mRNA

A ribosome becomes attached to the mRNA

A ribosome becomes attached to the mRNA Introduces the concept of the triplet code

p a codon U U U C G A U G C A U C G C A A C U C G C
the genetic code on the mRNA is read in groups of 3 letters called codons

p a codon codon codon codon codon codon codon
U U U C G A U G C A U C G C A A C U C G C the genetic code on the mRNA is read in groups of 3 letters called codons Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A aa1 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A aa1 tRNA molecules have specific anticodons for each of the 20 amino acids Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A aa1 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A aa1 the complementary anticodon is attracted to the first codon on the mRNA and forms a weak hydrogen bond. Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A G C U
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 the second codon on mRNA also attracts its complementary anticodon on tRNA Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 Shows the structure of tRNA including the anticodon a peptide bond is formed between the adjacent amino acids

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 The first tRNA molecule become detached from it’s amino acid Shows the structure of tRNA including the anticodon A C G aa3

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 The ribosome moves along the mRNA molecule A C G aa3 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 The ribosome moves along the mRNA molecule A C G aa3 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A G C U A C G
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 The third tRNA moves in place the anticodon linking with it’s complementary codon. Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 A peptide bond forms between the two amino acids Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 Shows the structure of tRNA including the anticodon

p codon codon codon codon codon codon codon
U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 Shows the structure of tRNA including the anticodon

a codon codon codon codon codon codon codon
U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A G C U A C G U A G
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 C G U aa5 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 C G U aa5 Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 C G U aa5 Shows the structure of tRNA including the anticodon

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 C G U aa5 U G A aa6 Shows the structure of tRNA including the anticodon

p codon codon codon codon codon codon codon
U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 C G U aa5 U G A aa6 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A G C U U A G A C G
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 U A G aa4 A C G aa3 C G U aa5 U G A aa6 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C A A A G C U A C G C G U
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 C G U aa5 U A G aa4 U G A aa6 Shows the structure of tRNA including the anticodon

a codon codon codon codon codon codon codon
U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 C G U aa5 A C G aa3 U A G aa4 U G A aa6 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C C G U A A A G C U A C G
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C C G U aa5 A A A aa1 G C U aa2 A C G aa3 U A G aa4 U G A aa6 Shows the structure of tRNA including the anticodon

U U U C G A U G C A U C G C A A C U C G C C G U A A A G C U A C G
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C C G U aa5 A A A aa1 G C U aa2 A C G aa3 U A G aa4 U G A aa6 Shows the structure of tRNA including the anticodon A stop codon is reached

codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A aa1 G C U aa2 A C G aa3 U A G aa4 C G U aa5 U G A aa6 Shows the structure of tRNA including the anticodon A stop codon is reached

A polypeptide chain has been formed and is released into the cytoplasm
codon codon codon codon codon codon codon U U U C G A U G C A U C G C A A C U C G C A A A G C U A C G U A G C G U U G A A polypeptide chain has been formed and is released into the cytoplasm Shows the structure of tRNA including the anticodon aa1 aa2 aa3 aa4 aa5 aa6

Shows how several ribosomes may read a piece of mRNA at once aa1 aa2 aa3 aa4 aa5 aa6

several ribosomes may pass along the mRNA behind the first - each producing an identical polypeptide Shows how several ribosomes may read a piece of mRNA at once aa1 aa2 aa3 aa4 aa5 aa6

A A A + aa1 Shows how tRNA is reactivated

A A A ATP AMP + aa1 Shows how tRNA is reactivated

A A A aa1 A A A ATP AMP + aa1 Shows how tRNA is reactivated

A A A aa1 A A A ATP AMP + aa1 Shows how tRNA is reactivated the tRNA molecules are activated after use by recombining with their specific amino acid

Processing and Packaging
Learning Intentions Explain how the polypeptide chain produced in translation becomes a protein and how the protein is processed.

Let’s have a re-cap!

The Genetic code The sequence of bases on DNA is a ‘codeword’
The four bases are ‘read’ in triplets. The combination of four letters in groups of 3 gives 64 base triplets. These 64 triplets code for the 20 amino acids. There is therefore more that one triplet that will code for each amino acid = degenerate Combinations of these 20 amino acids give rise to the huge variety of proteins found. The code never overlaps.

Think, Pair, Share What do you already know about DNA?

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Think, Pair, Share What do you already know about DNA?

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