LABORATORY REVIEW
MOLECULAR BIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Some amino acids are coded for by more than one codon.
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There are differences between the base sequences of genes in different species.
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In some organisms the genetic code for mitochondria differs from the genetic code for the nucleus.
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Some codons code for the addition of an amino acid and some code for the termination of translation.
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Detailed explanation-1: -Non-universal genetic codes are frequently found in animal mitochondrial decoding systems. In squid mitochondria, four codons deviate from the universal genetic code, namely AUA, UGA, and AGA/AGG (AGR) for Met, Trp, and Ser, respectively.
Detailed explanation-2: -Some mitochondrial DNA molecules harbor the mutation, whereas others do not. Because each cell can have hundreds of mitochondria, and each mitochondrion may have several copies of the genome, virtually any percentage of mitochondrial DNA may be mutant.
Detailed explanation-3: -The genetic code is not quite universal. The rare variations that we know of reveal selective pressures on the code and on the translation machinery. New data suggest the code changes through ambiguous intermediates and that termination is context dependent.