Genetics Ch. 14

What is a peptide bond?

A covalent bond formed between the carboxyl group of one amino acid and the amino group of another amino acid to form a peptide chain.

Which of the following features is an example of protein tertiary structure?

A disulfide bond between cysteine R groups

Which chemical group of an amino acid determines the type of the amino acid?

Radical group

Eukaryotic, but not bacterial, mRNAs are post-transcriptionally modified by the addition of a 5' cap and a 3' poly A-tail. These modifications allow eukaryotic mRNAs:

to persist longer in the cell before they are degraded.

What is a protein domain?

A stably folded region of a protein

Which of the following mechanisms is one way that exon shuffling is thought to occur?

An error in recombination such as crossing over at non-homologous sequences

Below is the biochemical pathway for the synthesis of a nutrient in Neurospora. Enzyme A Enzyme B Enzyme C Precursor intermediate 1 intermediate 2 nutrient Assume a Neurospora mutant strain cannot make the nutrient from the biochemical pathway above unless it is grown on minimal media that contains intermediate 1. This strain is likely to have a mutation in the gene encoding which of the following enzymes?

Enzyme A

Alpha helices and beta-pleated sheets are examples of protein secondary structures. How are these structures stabilized?

Hydrogen bonds between the carboxyl groups and amino groups of different amino acids

The major components of the ribosome are:

rRNA and protein.

During translation elongation in bacteria, peptide bond formation is catalyzed by:

ribozyme activity of the 23S rRNA.

What is an advantage of closed loop translation found in eukaryotic cells?

It allows for efficient re-use of ribosomes.

The one gene: one enzyme hypothesis made in the 40's was later modified to one gene: one polypeptide because:

not all proteins are enzymes.

What is aminoacylation or charging of a tRNA?

Covalent linkage of an amino acid to the appropriate tRNA molecule.

What evidence from high resolution crystal structures of the ribosome most strongly supports the idea that ribozymes are important for translation?

The interface between the two ribosomal subunits is comprised mostly of RNA.

Beadle and Tatum generated nutritional mutants of Neurospora to study biochemical pathways in this organism. After exposing Neurospora spores to UV light or X rays, how did the researchers know if a strain did NOT contain a nutritional mutant?

The strain can grow on minimal media.

Which of the following mechanisms do eukaryotic cells use for dealing with some misfolded proteins?

They are degraded by the proteasome.

What is an anticodon?

Three nucleotides of a tRNA molecule that are complementary to a codon sequence on an mRNA

In an experiment, scientists charged all tRNAs with the CAA anticodon for Leu with the amino acid Tyr. In the polypeptides made during this experiment,:

a Tyr would be added to the protein when the ribosome reaches a UUG codon for Leu in an mRNA.

When one of three stop codons reaches the A site of the ribosome, the stop codon is recognized by:

a release factor.

In bacteria, the Shine-Dalgarno sequence facilitates translation initiation by:

base pairing with the 16S rRNA in the small subunit of the ribosome.

The process of breaking down a larger molecule into smaller molecules accompanied by the release of energy is called:

catabolism.

In bacteria, the three rRNA genes are transcribed from DNA as a long initial RNA that is cleaved into three shorter rRNAs. This mechanism of transcription:

ensures that equal amounts of each rRNA are made to be assembled into ribosomes.

Enzymes are proteins that catalyze biological reactions; they function by:

lowering the activation energy of a reaction.

Vernon Ingram was able to determine that the mutant hemoglobin protein was different than the wild type hemoglobin protein by:

using protein fingerprinting to show a fragment of the mutant protein had different chemical properties.