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Biology - Coggle Diagram
Biology
Protein synthesis
Only 3 codons are stop codons, end of a polypeptide chain. One codon is the start codon. ATG. Genetic code is universal, same in all organisms.
translation- newly synthesised mRNA travels into cytoplasm. With tRNA and ribosomes, sequences in mRNA are used to build the polypeptide.
Transcription- transferring relevant segments of the genetic code from DNA to mRNA. This takes place in the nucleus. Purpose is to create mRNA. Ribosome is for proton synthesising but is in the cytoplasm, so smaller set of DNA to carry the sequence.
Gene codes for a protein, needs to make the amino acids, each codon codes for a different amino acid. A codon is 3 bases. Each codon encodes a specific amino acid. Codons cannot overlap. Codons are degenerate, some amino acids to make proteins can be specified by more than one codon.
Transcription: DNA separated into two strands by RNA polymerase.begins at promoter region, signals to RNA polymerase that it starts there. Opposite strand to antisense strand should be copied. mRNA built upon antisense strand. RNA polymerase builds RNA. Works in a 5'-3'. Ends at terminator region, signalling the end of the gene. Release mRNA and rewind the DNA. Completed mRNA undergoes editing to become mature, which leaves the nucleus to the cytoplasm.
Translation: Mature mRNA used as a template to create polypeptide chain. Protein synthesis occurs in ribosome. Occurs at the start codon, tRNA will recognise the start codon, another tRNA joins to the next codon of the mRNA. Ribosome catalyses the peptide bond formation. tRNA released to repeat the process. Ends at stop codon. No tRNA molecules to recognise this, so synthesising the chain is terminated.
DNA
DNA is a polynucleotide. Nucleotide bonded together in a chain. DNA made up of two chains, running in opposing directions- antiparralel. Each strand is made up of alternating deoxyribose sugars, and phosphate groups. Sugar phosphate backbone. (covalent phosphodiester bonds) 5-3.3-5. Carbon links. Antiparralel so run opposite ways.
Double helix structure: 3D shape consisting of the two polynucleotide chains, is in a double helix for strength, but can unwind for DNA replication as the hydrogen bonds are weak.
Hydrogen bonds: The polynucleotide strands are held together by hydrogen bonds, individually weak. Pairs the same bases A,T C,G. Complementary base pairs
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Mutations occur when the sequence of a base in a gene becomes altered. Caused by mutatic agents like chemicals. This results in the wrong polypeptide chain being made. 3 types: Deletions- multiple bases deleted from the gene. Substitutions- one or more in original gene get swapped. Insertion- one or more bases get added to original gene.
Genes
Specific sequence of DNA bases which code for particular proteins or functional RNA. Genes made for coding DNA sequences.
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Each gene has a unique base sequence of DNA. Either of the four base pairs, nucleotides. The order is specific to the gene.
