Question

1. when transcriptional regulator proteins bind to the dna double helix, how are they typically able to recognize the dna sequence information? a. by opening the double helix and reading the internal bases. b. by using the distinctive pattern exposed at the edge of each base pair on the dna surface. c. by binding solely to the minor groove. d. by chemically disrupting the base pair hydrogen bonds. e. by relying only on covalent interactions. 14. a bacterial cell is deficient in the amino acid tryptophan (trp). based on the tryptophan operon, how should the level of expression of enzymes needed to make trp be regulated? a. repressed, as trp is abundant. b. repressed, because the inactive repressor is constitutively expressed. c. expressed, as the bacterium needs the enzymes to synthesize trp. d. expressed, only if tfiid is released from the promoter. e. subject to alternative splicing. 15. what types of bonds hold the linear sequence of amino acids (primary structure) together in a polypeptide chain? a. peptide bonds b. ionic bonds c. hydrogen bonds d. disulfide bridges e. noncovalent bonds 16. what is the result of a nonsense mutation? a. a change in a single amino acid in the whole polypeptide chain. b. the addition of extra amino acids onto the end of the polypeptide chain. c. a completely jumbled sequence of amino acids. d. a premature termination of the polypeptide chain. e. the addition of extra amino acids to the n - terminal end of the growing polypeptide chain. 17. what structural element of a polypeptide is formed between the n - h and c=o of the polypeptide backbone and does not directly involve r - groups? a. primary structure b. secondary structure c. tertiary structure d. quaternary structure e. domain structure 18. what does the observation that a neuron and a liver cell have the same genome but express different rnas and proteins demonstrate? a. that the cells must have undergone genetic mutation since differentiation. b. that all gene expression is regulated solely at the translational level. c. that differences in cellular function are driven by differential gene expression. d. that the genome sequence changes in response to external signals. e. that only 50% of genes are used in any given organism. 19. activator proteins recruiting histone acetyltransferases (hats) ultimately promotes transcription by what mechanism? a. hats add acetyl groups to histone tails, increasing the affinity for the negatively charged dna, closing nucleosomes. b. hats remove acetyl groups, making the tails more positive, increasing dna affinity. c. hats add acetyl groups, making the tails less positive, lowering dna affinity for dna, thus opening nucleosomes and activating transcription. d. hats directly recruit the rna polymerase ii subunit ctd. e. hats prevent the binding of chromatin - remodeling complexes.

Explanation:

1. Transcriptional regulator proteins recognize DNA sequences by using the distinctive pattern exposed at the edge of each base - pair on the DNA surface.
2. When a bacterial cell is deficient in tryptophan, the enzymes needed to make tryptophan should be expressed as the bacterium needs them for synthesis.
3. Peptide bonds hold the linear sequence of amino acids together in a polypeptide chain.
4. A nonsense mutation results in a premature termination of the polypeptide chain.
5. The secondary structure of a polypeptide is formed between the N - H and C=O of the polypeptide backbone and does not directly involve R - groups.
6. The fact that a neuron and a liver cell have the same genome but express different RNAs and proteins demonstrates that differences in cellular function are driven by differential gene expression.
7. HATs add acetyl groups to histone tails, making the tails less positive, lowering DNA affinity for DNA, thus opening nucleosomes and activating transcription.

Answer:

1. b
2. c
3. a
4. d
5. b
6. c
7. c