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Flashcards in Lesson 7 Translation Deck (49)
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What is an inborn error of metabolism?

A relationship between the function of gene and the production of enzymes.


What did Beadle and Tatum's Experiments with Neurospora lead to?

The One Gene-One Enzyme theory


What is a loss of function allele?

A gene that loses its function causes a defect.


What is the genetic code? How is it read?

A sequence of bases within an mRNA molecule.
Read in groups of three nucleotides.


How many types of bases are there?

4. A, U, G, C


How many different codon arrangements exist?

4 to the third power or 64


What is meant by saying genetic code is degenerate?

There are more codon than amino acids. More than one codon specifies the same amino acid.


What is the wobble base?

The third base in the codon, which is usually the degenerate base.


Experiment 13A: Deciphering the Genetic Code
What was the hypothesis of the experiment?

The sequence of bases in RNA determines the incorporation of specific amino acids into a polypeptide.


Experiment 13A; Deciphering the Genetic Code
How were the data interpreted?

Investigators were able to determine how many Us or G's in the codon for a specific amino acid, but not the order of those bases.


Primary structure of a polypeptide

Amino acid sequence


What is a quaternary structure? What are its subunits?

Structure of a protein made up of more than one polypeptide. Each polypeptide is a subunit of the protein.


What kind of functions do proteins carry out?

A myriad of cellular functions, including the synthesis of all of a cell's molecules and macromolecules.


What does the function of tRNA depend on?

The specificity between the amino acid it carries and its anticodon.


What is the function of tRNA?

To recognize the codon within an mRNA and carry the correct amino acids to the site of polypeptide synthesis.


How do mRNA and tRNA bind?

The anticodon in a tRNA molecules binds to a codon in mRNA because of their complementary sequences.


Of what codons is the genetic code made?

The genetic code has 3 stop codons and 61 different codons that specify the 20 amino acids.


Experiment 13B: Translation, mRNA, tRNA
What is the hypothesis?

Codon recognition is dictated only by the tRNA anticodon; the chemical structure of the amino acid attached does not play a role.


Experiment 13B: Translation, mRNA, tRNA
What does Raney nickel do?

It converts cysteine to alanine. It was the only way to find an alanine in the experiment because the only codon in the template were U any G.


How does Raney nickel convert cysteine to alanine?

It removes the -SH group. It does not remove the 14C label within the cysteine.


Experiment 13B: Translation, mRNA, tRNA
Why was column chromatography used?

To separate the amino acids. Alanine and cysteine come out in different fractions.


Experiment 13B: Translation, mRNA, tRNA
How were the data interpreted?

In the control, the radioactivity was mostly with cysteine. In other set, the radioactivity was mostly with alanine. This means tRNA incorporated alanine into the polypeptides. It was tRNAcys codons that incorporated the amino acid, so it depends on tRNA and mRNA, no on amino acid itself.


What common structural features do tRNAs share?

They have a secondary structure that is described as a cloverleaf pattern. There are three stem/loop structures, a variable region, an acceptor stem, and a 3' single-stranded region.


Where is the anticodon located on tRNA?

In the second stem/loop region.


What are aminoacyl-tRNA synthetase enzymes?

Enzymes that catalyze the attachment of amino acids to tRNA molecules. There are twenty different ones.


What is a charged tRNA?

A charged tRNA has an amino acid attached to its 3' end by an ester bond.


Where does the wobble position occur?

Between the first base (meaning first base in the 5' to 3' direction) in the anticodon ant the third base in the mRNA


What is the wobble hypothesis?

The first two positions pair strictly according to AU/GC rule. Third position can tolerate certain types of mismatches.


What kind of ribosomes do prokaryotes and eukaryotes have?

Prokaryotes: one type of ribosomes found within bacterial cytoplasm.
Eukaryotes: biochemically distinct ribosomes in different cellular locations.


What does each ribosomes contain?

Several rRNA molecules and many proteins.