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BIO 325_Genetics > Chapter 13_Translation Of mRNA > Flashcards

Chapter 13_Translation Of mRNA Flashcards

1
Q

One Gene One Enzyme Hypothesis

A

A single gene controls the synthesis of a single enzyme.

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2
Q

Polypeptide

A

A linear sequence of amino acids.

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3
Q

Protein

A

Composed of polypeptides.

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4
Q

Translation

A

Involves the translation of a nucleotide sequence (mRNA) into an amino acid sequence (polypeptide).

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5
Q

Sense Codon

A

The sequence of three bases in most codons specifies a particular amino acid.

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6
Q

Start and Stop Codons

A
  • Start: AUG (Methionine)

- Stop: UAA, UAG, and UGA

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7
Q

Anticodons

A

3 nucleotide sequence that is complementary to codons in mRNA.

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8
Q

The genetic code is degenerate, which means…

A

…more than one codon can specify the same amino acid.

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9
Q

Reading Frame

A

A sequence of codons determined by reading bases in groups of three, beginning with the start codon.

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10
Q

Peptide Bond

A

Formed between the carboxyl group in the last amino acid of the polypeptide chain and the amino group in the amino acid being added.

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11
Q

N-Terminus

A

(Amino Terminal End) The first amino acid is located here. The 5’ end.

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12
Q

C-Terminus

A

(Carboxyl Terminal End) The last amino acid is located here. The 3’ end.

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13
Q

Side Chain

A

(R group) Each amino acid contains a unique side chain.

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14
Q

Nonpolar, Aliphatic Amino Acids

A

Glycine, Alanine, Valine, Leucine, Isoleucine, Proline, Cysteine, Methionine

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15
Q

Aromatic Amino Acids

A

Phenylalanine, Tyrosine, Tryptophan

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16
Q

Polar Neutral Amino Acids

A

Serine, Threonine, Asparagine, Glutamine

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17
Q

Polar Acidic Amino Acids

A

Aspartic Acid, Glutamic Acid

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18
Q

Polar Basic Amino Acids

A

Histidine, Lysine, Arginine

19
Q

Nonstandard Amino Acids

A
  • Selenocysteine
  • Pyrrolysine
  • Occasionally incorporated into polypeptides by the use of stop codons.
20
Q

When does the folding process begin?

A

While the polypeptide is still being translated.

21
Q

The progression from the primary structure of a polypeptide the the 3D structure of a protein is dictated by…

A

…the amino acid sequence within the polypeptide. In particular, the chemical properties of the amino acid side chains play a central role in determining the folding pattern of a protein.

22
Q

Chaperones

A

Proteins that bind to polypeptides and facilitate their proper folding.

23
Q

Secondary Structure

A
  • The first stage of folding involves the formation of a regular, repeating shape (the secondary structure)
  • Comes in the form alpha helix and the beta sheet.
  • A single polypeptide may have some regions that fold into an alpha helix and other regions that fold into a beta sheet.
24
Q

Tertiary Structure

A

Short regions of secondary structure within a polypeptide are folded relative to each other. This is a thermodynamically favorable process.

25
Q

Quaternary Structure

A

Proteins composed of two or more polypeptides that associate with each other to make a functional protein.

26
Q

Adaptor Hypthesis

A

The position of an amino acid within a polypeptide chain is determined by the binding between the mRNA and an adaptor molecule carrying a specific amino acid.

27
Q

Aminoacyl-tRNA Synthetases

A

Catalyze the attachment of amino acids to tRNA molecules. Cells produce 20 different of these, 1 for each of the 20 distinct amino acids.

28
Q

Charged tRNA

A

(Aminoacyl-tRNA) The amino acid is attached to the 3’ end of the tRNA by a covalent bond.

29
Q

Catalytic function of aminoacyl-tRNA synthetase

A
  • An amino acid and ATP bind to the enzyme. AMP is covalently bound to the amino acid, and pyrophosphate is released.
  • The correct tRNA binds to the enzyme. The amino acid becomes covalently attached to the 3’ end of the tRNA. AMP is released
  • The “charged” tRNA is released.
30
Q

Isoacceptor tRNA

A

When two or more tRNAs that differ at the wobble base are able to recognize the same codon.

31
Q

Ribosome

A

The macromolecular arena where translation takes place.

32
Q

Bacterial and Eukaryotic Ribosomes are assembled from…

A

…rRNA and proteins

33
Q

Small and Large Subunits

A
  • Bacteria: 30s (Small) + 50s (Large) = 70s

- Eukaryoitc: 40s (Small) + 60s (Large) = 80s

34
Q

Nucleolus

A

Where the assembly of the rRNAs and ribosomal proteins to make the 40s and 60s subunits.

35
Q

Ribosomes contain discrete sites where tRNAs bind and the polypeptide is synthesized.

A
  • The two sites for tRNA binding to the robosome are peptidyl and aminoacyl site.
  • A third site is called the exit site.
36
Q

Stages of Translation

A
  • Initiation: The ribosomal subunits, mRNA, and the first tRNA assemble to form a complex.
  • Elongation: The ribosome slides along the mRNA in the 5’ to 3’ direction, moving over the codons.
  • Termination: A stop codon is reached. Disassembly occurs, and the newly made polypeptide is released.
37
Q

Initiator tRNA

A

Recognizes the start codon in the mRNA.

38
Q

Describe initiation

A
  • IF1 and IF3 bind to the 30S subunit.
  • IF2, which uses GTP, promotes the binding of the initiator tRNA to the start codon in the P site.
  • IF1 and IF3 are released.
  • IF2 hydrolyzes its GTP and is released.
  • The 50S subunit associates.
39
Q

Shine-Dalgarno Sequence

A

A nine nucleotide sequence within BACTERIAL mRNA. Facilitates the binding of mRNA to the ribosome.

40
Q

Describe Elongation

A
  • A charged tRNA binds to the A site. EF-Tu facilitates tRNA binding and hydrolyzes GTP.
  • Peptidyltransferase, which is a component of the 50S subunit, catalyzes peptide bond formation between the polypeptide chain and the amino acid in the A site. The polypeptide is transferred to the A site.
  • The ribosome translocates 1 codon to the right. This translocation is promoted by EF-G, which hydrolyzes GTP.
  • An uncharged tRNA is released from the E site.
  • This process is repeated, again and again, until a stop codon is reached.
41
Q

Decoding function

A

16S rRNA can detect when an incorrect tRNA is bound at the A site and will prevent elongation until the mispaired tRNA is released from the A site. It is important in maintaining high fidelity of mRNA translation.

42
Q

Peptidyl transfer

A

The polypeptide is removed from teh tRNA in the P site and transferred to the amino acid at the A site.

43
Q

Release Factors

A

Molecular mimics that resemble the structure of tRNAs.

44
Q

Describe Termination

A
  • tRNA in P site carries completed polypeptide.
  • A release factor (RF) binds to the A site.
  • The polypeptide is cleaved from the tRNA in the P site. The tRNA is then released.
  • The ribosomal subunits mRNA, and release factor dissociate.

BIO 325_Genetics (17 decks)

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