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Pack 9 - DNA, genes and chromosomes. DNA and protein synthesis - Coggle…
Pack 9 - DNA, genes and chromosomes. DNA and protein synthesis
Translation
mRNA attaches to a ribosome in the cytoplasm. Amino acids are placed in the correct order using transfer RNA (tRNA)
tRNA
Single stranded but folded back on itself leaving 3 unpaired nitrogen bases the Anticodon. Said to have a structure resembling a clover leaf
Each tRNA molecule carries a specific amino acid and attached by a specific activating enzyme (Aminoacyl - tRNA synthase) using energy from the hydrolysis of ATP
How is tRNA adapted?
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Contains an anticodon that is complementary to the codon on the mRNA - this pairing determines the order of the amino acids
Is more stable than mRNA allowing it to pick up another amino acid once it has carried one off in a polypeptide
Once the amino acids are in the correct sequence, peptide links form between them forming a polypeptide
mRNA attached to the ribosome is read in groups of 3 called codons. The nitrogen bases in the anticodons on the tRNA pair up with the codons on the mRNA
Ribosomes
Each ribosome is made of two units - 1 small, 1 large. they occur in groups called polyribosomes or polysomes and are held together by a thin strand of rRNA
Transcription
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Transcription factors
Protein that binds to specific DNA sequences, controlling the rate of transcription of genetic information from DNA to mRNA
Move from cytoplasm to DNA, bind to a specific gene - promoter region, Allow/ inhibit the binding of RNA polymerase
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Genes
3 nucleotides code for 1 amino acid - triplet code as using 2 =16 different amino acids which isn't enough for the 20 amino acids needed.
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Genetic code is also non-overlapping -each base is only read once and also Universal - same triplet codes for the same amino acids in all living organisms (except a few)
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