OBJECTIVE LIFE SCIENCE
MOLECULAR BIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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All living organisms have the same DNA
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All human cells have the same 46 chromosomes
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All species use the same DNA codon amino acid pairings
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Living organisms share a common ancestor
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Detailed explanation-1: -A codon is a DNA or RNA sequence of three nucleotides (a trinucleotide) that forms a unit of genomic information encoding a particular amino acid or signaling the termination of protein synthesis (stop signals). There are 64 different codons: 61 specify amino acids and 3 are used as stop signals.
Detailed explanation-2: -The genetic code is universal because all species use the same four bases A, T, C and G, and each base sequence codes for the same amino acid in all species. despite the 64 possible codons (sequence of three bases), there are only 20 possible amino acids.
Detailed explanation-3: -With three bases, there are 43 = 64 codons, which is more than enough to encode the 20 amino acids. Therefore, the genetic code is degenerate, which means more than one triplet can encode the same amino acid.