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Cellular Control revision…read more

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Structure of DNA
Adenine = Thymine (2 Hydrogen bonds)
Cytosine = Guanine (3 Hydrogen bonds)
Deoxyribose sugar and phosphate
Pyrimadines: Single ring. C and T
Purines: Double ring. A and G…read more

Slide 3

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The genetic code
· A group of 3 bases codes for one amino acid. This is a base triplet
· Only one strand of DNA codes for proteins = reference strand
· Gene ­ a length of DNA that codes of one polypeptide.
Codes for...
A A T Leucine…read more

Slide 4

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Protein Synthesis - Transcription
1. Hydrogen bonds between bases broken by DNA Helicase ­ DNA unzips
2. Free nucleotides diffuse into position with exposed bases on reference
strand, using complemetary base pairing.
3. Condensation reactions catalysed by RNA polymerase creates mRNA.
4. mRNA molecule breaks free from DNA and leaves the nucleus through a
nuclear pore. Arrives in the cytoplasm and moves to a ribosome.…read more

Slide 5

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Protein Synthesis - Translation
· tRNA molecules are used ­ have a series of 3 bases called an anti-codon
· In the cytoplasm, tRNA transferases load AAs onto specific tRNA
molecules, depending on their anti-codon.
1. In the ribosome, there is complementary base pairing between codons and
2. Another tRNA molecule approaches and joins.
3. A condensation reaction forms a peptide bond between the 2 AAs.
4. The mRNA moves, and the first tRNA leaves
5. Another amino acid is brought in.
6. A chain of AA's continues to be built up until a stop codon is reached on
the mRNA.…read more

Slide 6

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Chain of
Petide bond
Amino acids
Codon/ Ribosome
base triplet…read more

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