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24 Cards in this Set
- Front
- Back
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What is the statement that is known as Central Dogma (Watson and Crick)?
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"Within each cell, genetic information flows from DNA to RNA to protein."
"Once 'information' is passed into protein, it cannot get out again." maintains that genetic information flows in two distinct stages |
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Explain the flow of genetic information from DNA to RNA to protein.
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In transcription, the enzyme RNA polymerase copies DNA to produce an RNA transcript.
In translation, the cellular machinery uses instructions in mRNA to synthesize a polypeptide, following the rules of the genetic code. |
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What is the term that describes the conversion of DNA-encoded information to its RNA-encoded equivalent?
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transcription
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What is the term that describes the decoding of nucleotide information to a sequence of amino acids, which translates mRNA into its polypeptide equivalent?
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translation
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Where does translation take place?
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on ribosomes, which are composed of proteins and ribosomal RNAs (rRNAs)
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What is the genetic code?
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the sequence of nucleotides, coded in triplets, that determines the sequence of amino acids in protein synthesis
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What is represented by each amino acid?
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a codon --> a triplet of nucleotides in a messenger RNA
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How many amino acids are on the accepted list created by Watson and Crick?
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20 amino acids
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How many nucleotides encode for the 20 amino acids?
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4 nucleotides
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How many triplet codons are there total?
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4^3 = 64 triplet codons
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_____ codons represent the 20 amino acids, while ____ codons signify stop.
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61 = amino acids
3 = stop |
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The code is read from left to right, which corresponds to which direction along mRNA?
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5' --> 3'
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Which scientist was the first to compare maps of mutations within a gene to the particular amino acid substitutions that resulted?
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Charles Yanofsky --> looked at order of DNA mutations and order of amino acid sequence changes
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What was Charles Yanofsky's conclusion?
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The order of mutations mapped within the DNA of the gene by recombination was indeed collinear with the positions of the amino acid substitutions of the encoded polypeptide.
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Yanofsky observed that _________________ may affect the same amino acid. What did he conclude from this?
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point mutations (changes in only one nucleotide pair)
A codon must contain more than one nucleotide. |
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Yanofsky observed that each of the point mutations in the tryptophan synthetase gene altered the identity of __________ amino acid. What did he conclude from this?
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only one
Each nucleotide influences the identity of only one amino acid. Codons for amino acids do not overlap. |
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Proflavin does not cause base substitutions. Instead, what does it cause?
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deletions or insertions --> can insert between two adjacent base pairs
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What caused genes with proflavin-induced mutations to revert to wild-type?
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Only further exposure to proflavin caused proflavin-induced mutations to revert to wild type.
Genes with proflavin-induced mutations did not revert back to wild-type upon treatment with other mutagens known to cause nucleotide substitutions. |
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What did the proflavin reversion suggest to Crick and Brenner?
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Each codon is a trio of nucleotides and for each gene there is a single starting point.
The starting point establishes a reading frame --> the sequence of codons starting with AUG and ending with a termination codon |
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If codons are read in order from a fixed starting point, one mutation will counteract another if two are equivalent mutations of opposite signs (-) and (+). What does this mean?
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Each insertion counterbalances each deletion, which restores the reading frame.
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How many changes of the same sign must occur in a gene for the encoded polypeptide to sustain function?
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three or multiples of three (deletions or insertions)
will give wild type supports deduction |
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A single nucleotide inserted into or deleted from a gene alters the __________________ and thereby affects the identity of not only one but all other amino acids beyond the point of alteration.
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reading frame
This is known as a frameshift mutation --> destroys function of gene |
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Most amino acids are encoded by _____________ codon.
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more than one
suggests that the genetic code is degenerate: Two or more nucleotide triplets specify most of the 20 amino acids. |
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What processes restore the reading frame?
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three or multiples of three deletions and insertions
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