RNA is single stranded substitutes the sugar ribose for deoxyribose and the

Rna is single stranded substitutes the sugar ribose

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RNA is single-stranded; substitutes the sugar ribose for deoxyribose and the base uracil for thymine Messenger RNA or mRNA, conveys the DNA recipe for protein synthesis to the cell cytoplasm . mRNA binds to ribosome , each three-base codon of the mRNA links to a specific form of transfer RNA (tRNA) containing the complementary three-base sequence. This tRNA, in turn, transfers a single amino acid to a growing protein chain. Each codon directs the addition of one amino acid to the protein. Note: the same amino acid can be added by different codons; in this illustration, the mRNA sequences GCA and GCC are both specifying the addition of the amino acid alanine (Ala).
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Important Both DNA and RNA have a direction: one end is the 3’ the other is the 5’ end. Thus, _codons_ are read in one direction only. Also, note there is redundancy in the genetic code: the different sequences can specify for the same amino acid. Example: UUA and UUG = Leucine
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When things go wrong… Mutations : changes in the DNA sequence, that may be passed along to future generations. Point mutations : a single base substitution THE CAT SAW THE R AT THE CAT SAW THE H AT Deletion : a small DNA segment is lost THE C AT SAW THE RAT THE AT SAW THE RAT Insertion : a segment of DNA is added THE CAT SAW THE RAT THE C H AT SAW THE RAT
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Mutations Frame- _shift_ mutation : modification of the reading frame after a deletion or insertion, resulting in all codons downstream being different. For example: THE RAT SAW THE CAT AND RAN If you take out the “R” in “RAT” and shift the frames, you get: THE ATS AWT HEC ATA NDR AN The resulting sentence (or mRNA message) is meaningless! THE OLD MAN AND THE SEA THE LDM ANA NDT HES EA
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Somatic Mutations Somatic mutations: occur in _body_ cells, or cells that do not lead to gametes. Somatic mutations that occur in leaves, roots or stems are usually not passed on to future generations… UNLESS the plant reproduced _asexually_ .
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