TLS Online TPP Program

#Question id: 1075


The clustered, regularly interspaced short palindromic repeats (CRISPR) system in bacterial cells has been called the “immune” system of bacteria. CRISPR protect bacteria from a repeat infection from the same phage because bacterial cells

#Unit 4. Cell Communication and Cell Signaling
  1. recognize proteins on the surface of the phage and secrete enzymes that digest the phage.

  2. recognize proteins on the surface of the phage and secrete proteins that block the binding of the phage.

  3. integrate fragments from the phage DNA in their own chromosomes and target for destruction any DNA that contains the same fragments in the future.

  4. modify the attachment sites for the phages so that new infections cannot take place.

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TLS Online TPP Program

#Question id: 11157

#Unit 9. Diversity of Life Forms

Typically, mutations that modify the active site of an enzyme are more likely to be harmful than mutations that affect other parts of the enzyme. A hypothetical enzyme consists of four domains (A—D), and the amino acid sequences of these four domains have been determined in five related species. Given the proportion of amino acid homologies among the five species at each of the four domains, which domain probably contains the active site?


TLS Online TPP Program

#Question id: 11158

#Unit 9. Diversity of Life Forms

Which of these items does not necessarily exist in a simple linear relationship with the number of gene-duplication events when placed as the label on the vertical axis of the graph below?

TLS Online TPP Program

#Question id: 11159

#Unit 9. Diversity of Life Forms

Which kind of DNA should provide the best molecular clock for gauging the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?

TLS Online TPP Program

#Question id: 11160

#Unit 9. Diversity of Life Forms

A phylogenetic tree constructed using sequence differences in mitochondrial DNA would be most valid for discerning the evolutionary relatedness of

TLS Online TPP Program

#Question id: 11161

#Unit 9. Diversity of Life Forms

The lakes of northern Minnesota are home to many similar species of damselflies of the genus Enallagma that have apparently undergone speciation from ancestral stock since the last glacial retreat about 10,000 years ago. Sequencing which of the following would probably be most useful in sorting out evolutionary relationships among these closely related species?

TLS Online TPP Program

#Question id: 11162

#Unit 9. Diversity of Life Forms

Which statement represents the best explanation for the observation that the nuclear DNA of wolves and domestic dogs has a very high degree of homology?