BY123 Exam 4

• By bombarding fungus Neurospaora Crassa with X-Rays, Beadle and Tatum were able to study nutritional mutants and characterize enzymes in a biochemical pathway
• In eukaryotic cells, a signal peptide by a signal-recognition particle targets a growing peptide to the ER
• Bacteria can transcribe and translate human genes to produce functional human proteins because the genetic code is nearly universal
• Polysomes are groups of ribosomes
• SnRNPS are part of a spliceosome
• How are polypeptides modified post-translation?

  Cleave of a polypeptide in 2 or more chains
• MicroRNAs binding to complementary sequences on an mRNA results in either?

  Blocking translation or degrading the targeted mRNA
• Small noncoding RNAs(ncRNAs) called piwi-interacting RNAs, or piRNAs do what?


  induce the formation of heterochromatin and block the expression of movable DNA elements called transposons
• In a eukaryote, activating transcription factors may stimulate gene expression by binding to a DNA site called the?

  enhancer
• What is the guardian angel of the genome?

  p53 gene
• MyoD promotes muscle cell development by turning on the expression of ,multiple muscle-related genes
• genes for noncoding RNA makeup the majority of meaningful genetic information in the human genome
• in an inducible operon, the inducer is often the substrate in the pathway being regulated; the inducer binds to the repressor, thus rendering it inactive
• in addition to a promoter, eukaryotic genes have control elements called proximal control elements and distal enhancers
• in drosophila development, the anterior-posterior axis of embryo is determined by egg-polarity genes
• restriction enzymes?

  cut viral DNA once it has entered host cell
• RNA viruses mutate more quickly because RNA molecules do not go through proofreading
• viroids are circular DNA molecules that function like a virus in plants
• Class IV viruses are characterized by single-stranded RNA that serves as mRNA
• picornovirus is a virus without an envelope
• The avian flu has a higher mortality rate than swine flu
• virulent phages replicate through the lytic cycle only, and temperate phages replicate using both the lytic and lysogenic cycles
• lysogenic?

  phage that inserts itself into DNA of host cell
• prophage is viral DNA incorporated into a bacterial chromosome
• parovirus is not a class I virus
• vestigial structures are homologies that appear to have marginal importance to an organism
• what insight did Darwin gain from reading Thomas Malthus's essay on Human Suffering?

  organisms have the capacity to overproduce
• Even though rodents known as sugar gliders and flying squirrels are members of distinct groups of organisms and live on different continents, they possess similar characteristics. What is this an example of?

  convergent evolution
• on an evolutionary tree, homologous characteristics form a nest pattern
• how did Hutton and Lyell's ideas influence Charles Darwin thinking?

  Darwin reasoned that the earth must be very old and that slow, subtle processes could produce substantial biological changes
• endemic refers to organisms found only in a specific place in the world
• The modern idea of extinction as a common occurrence in Earth's history was first proposed in the early 19th century in the writing of..?

  cuvier
• Which of the following is a likely explanation of why natural selection favored the evolution of signals for sexual reproduction?

  even in the simplest organisms, sexual reproduction required several coordinated responses by cells
• in yeast signal transduction, the yeast cells secrete molecules that result in response by other yeast cells
• of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to?

  the active site of an allosteric enzyme that binds to a specific substrate?
• testosterone functions inside a cell by acting as a signal receptor that activates tyrosine kinases
• because most receptors are membrane proteins, which of the following is usually true?

  they change their conformation after binding with signal polypeptides
• since steroid receptors are located intracellularly, which of the following is true?

  the steroid/receptor complex can cross the nuclear membrane
• Receptor tyrosine kinases (RTKs) are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. This information can now be utilized in breast cancer treatment if which of the following is true?

  the patient's cancer cells have detectable HER2
• Which of the following is the best explanation for the inability of a specific animal cell to reduce the Ca2⁺ concentration in its cytosol compared with the extracellular fluid?

  insufficient ATP levels in the cytoplasm