BIO 240 Exam 4

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The distinct characteristics of different cell types in a multicellular organism result mainly from the _____.

transcriptional regulation of geneses


Which of the following statements about differentiated cells is false? a. some of the proteins found in differentiated cells are in all cells of a multicellular organism
b. once a cell has differentiated, it can continue to change its gene expression
c. cells of distinct types express nonoverlapping sets of transcription facts
d. once a cell has differentiated, it will no longer need to change its gene expression



the importance of the DNA sequence in the promoter region if its due to the need to make non-covalent interactions with amino acid side chains of DNA ploymerase.
a. true
b. false



the tryptophan operator ___________

binds to the tryptophan repressor when the repressor is bound to tryptophan


Which of the following statements about transcriptional regulators is false?
a. transcriptional regulators usually interact with the sugar-phosphate backbone on the outside of the double helix to determine where to bind in the DNA helix.
b. transcriptional regulators will form hydrogen bonds, ionic bonds, and hydrophobic interactions with DNA
c. the dan-binding motifs of transcriptional regulators regulators usually bond in the major groove of teh DNA-helix
d. The binding of transcriptional regulators generally doesnt disrupt the H bonds tab hold the double helix together



Which of the following statements about the LAc operon is case?

a The Lac repressor binds with the lactose is present in the cell


Which of the following about the proteasome is false?

Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome


The genes of a bacterial ______ are transcribed into a single mRNA. Many bacterial promoters contain a region known as a _______, t which specific transcription _______ binds. Genes in which transcription is prevented are said to be _________. Genes that are being ________ expressed are being transcribed all the time.

operon, operator, regulator, repressed, constitutively


which of the following statements about the cytoskeleton is false?

Protein monomers that are held together with covalent binds are form cytoskeletal filaments


Which of the following statements below about intermediate filaments is false?

Each filament is about 10 nanometers in diameter


The hydrolysis of GTP to GDP carried out by tubulin molecules ______.

allows the behavior of micro


What sequence most likely occurs at a gene promoter region



Which of the following statements about RNA splicing is false?

For a gene to function properly, every exon must be removed from the primary transcript in the same fashion every mRNA molecule produced from the same gene



25 nm


actin filaments

7 nm


intermediate filaments

10 nm


Which of the following statements about skeletal muscle contraction is false

The changes in voltage across the plasma memebrane taht cockers when a muscle cell receives a signal from the nervous system cause pumpuing of Ca=- into the sacroplsamic recticulum, triggering a muscle contracyion


In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by _______

scanning along themRNA from the 5' end


Actin microfilaments are always exhibit a highly dynamic structure
a. true
b. false



Which of the following statements is true?
a. rib are large rna structures composed solely of rRNA
b. rib are synthesized in cytoplasm
c, rRNA contains the catalytic activity that joins amino acids together
d. a ribosome binds one tRNA at a time



For a cell's genetic material to be used, the info is first copied from the DNA into the nucleotide sequence of RNA in a porcess called _______. Various kinds of RNA are produced, each with different functions. _________ molecules code for proteins, _______ molecules act as adaptors for protein synthesis, and ______ molecules are integral components of the ribosome.

transcription, mRNA, tRna, rRna


Intermediate filaments are found mainly in cells that are subject to mechanical stress. Mutations in genes that disrupt intermediate filaments cause some far human diseases. For example, the skin of people with epidermolysis bullosa simplex is very susceptible to mechanical injury; people wit this disorder have mutations in their ______ genes, the intermediate filament found in epithelial cells. These intermediate filaments are usually connected from cell to cell through junctions called _________s. The main filaments found in nuclei belong to the ______ family. In the nervous system, _____s help strengthen the extremely long extensions often present in nerve cell axons; disruptions in these intermediate filaments can lead to neurodegeneration.

keratin, desomosome, lamin, neurofilmaents


translations ends when the ribosome ________

reaches the stop codon


Which of the following structures shorten during muscle contraction



Microtubules are formed from tubiulin heterodimer, which is composed of the nucletide-binfing ______ protein toward the plus end and the ______ protein toward the minus end, Tubulin dimers are stacked together into protofilaments; ________n parallel prtofilaments from the tubelike structure of a microtubule. ______ rings are important for microtubule nucleations and are found in the centrosome, which is usually found near the nucleus of the cells.

B-tublin, a-tubulin, thirteen, y-tubulin


When protein is being synthesized via translation, what site in the sassembled ribosome would you expect to contain the tRNA attached to the growing polypeptife chain?



WHat portion of the tRna molecule is responsible for determining the mRNA sequence to which it binds?



Keratin, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments?

Phosphorylation causes during every mitotic cycle