Central Dogma & Protein Structure – Review Questions

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The flow of genetic information: DNA → RNA → Protein.
Francis Crick in 1958.
Transcription.
RNA polymerase.
At the ribosome in the cytoplasm.
Amino acids.
Its 3D structure, which is dictated by its amino acid sequence.
Structural support, catalysis (enzymes), transport, signaling, and defense.
On ribosomes, either free in the cytoplasm or bound to the rough ER.
Translation.
mRNA and other functional RNAs (tRNA, rRNA, regulatory RNAs).
Proteins, via mRNA translation.
A gene.
DNA.
Nucleotides.
A phosphate group, a sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base.
DNA: Adenine (A), Thymine (T), Guanine (G), Cytosine (C). RNA: A, Uracil (U), G, C.
Purines have two rings (A, G), pyrimidines have one ring (C, T, U).
1) DNA has deoxyribose sugar, RNA has ribose sugar.
2) DNA uses T, RNA uses U as a nitrogenous base.
The 5’ carbon of the sugar.
Deoxyribose lacks an oxygen on the 2’ carbon; ribose has a hydroxyl group on the 2’ carbon.
Phosphodiester bonds, linking the 3’ carbon of one sugar to the 5’ phosphate of the next nucleotide.
Uracil (U) lacks a methyl group that thymine (T) has; found in RNA instead of DNA.
5’ end: phosphate group. 3’ end: hydroxyl group of sugar.
Adenine, Uracil, Cytosine, Guanine.
rRNA and proteins.
To carry genetic information (mRNA) and assist in protein synthesis (tRNA, rRNA).
Carries the genetic code from DNA to the ribosome for protein synthesis.
Brings the correct amino acid to the ribosome matching the codon on mRNA.
That A pairs with T and G pairs with C in equal amounts; base-pair rules.
Complementary base pairing and double-helix structure.
X-ray crystallography.
1. DNA is helical
2. DNA is double-stranded
3. Bases are on the inside, backbone outside.
The two DNA strands run in opposite directions: one 5’→3’, the other 3’→5’.
A pairs with T, G pairs with C, forming hydrogen bonds between strands.
To maintain a uniform width of the DNA double helix.
20 amino acids.
The R-group (side chain).
Polarity, charge, and size.
Polar and charged R-groups bend toward water; nonpolar R-groups bend away from water.
Peptide bond.
A chain of amino acids linked by peptide bonds.
The sequence of amino acids.
A single amino acid substitution in hemoglobin changes its primary structure and alters function.
Hydrogen bonds between backbone atoms.
Alpha helices and beta-pleated sheets.
Alpha helices: bonds within same chain; Beta sheets: bonds between neighboring chains.
Hydrogen bonds, ionic bonds, hydrophobic interactions (and disulfide bridges sometimes).
The tertiary structure, or full 3D shape of the protein.