Genetic Code and 64 Codons

Three nucleotides in mRNA specify one amino acid in the polypeptide product; thus, each codon contains 3 nucleotides

A genetic code is composed of nucleotide triplets. What does this mean?

20

How many different amino acids are incorporated into polypeptides during translation?

64 four bases, three bases in a codon, 4^3 with 61 being amino acid combinations and 3 being chain termination signals

How many possible patterns for codons are there?

-Composed of nucleotide triplets -Non-overlapping -Comma-free (continuous) -Degenerate -Ordered -Organized by start and stop codons -Nearly universal

What are characterisitics of the gentic code?

Each nucleotide in mRNA belongs to just one codon except in rare cases where genes overlap and a nucleotide sequence is read in two different reading frames

What does it mean when a genetic code in nonoverlapping?

-no "punctuation" within coding regions of mRNA molecules -During translation, the codons are read consecutively

What does it mean when a genetic code is continuous (comma free)?

All but two of the amino acids are specified by more than one codon (an amino acid may be coded for by more than one codon)

What does it mean when a genetic code is degenerate?

With minor exceptions, the codons have the same meaning in all living organisms, from viruses to humans

What does it mean when a genetic code is nearly universal?

Multiple codons for a given amino acid and codons for amino acids with similar chemical properties are closely related, usually differing by a single nucleotide

What does it mean when a genetic code is ordered?

Specific codons are used to initiate and to terminate polypeptide chains

What does it mean when a genetic code is organized by start and stop codons?

set of rules used by living cells to translate information encoded within genetic material into proteins

What is the genetic code?