Another application of the polymerase chain reaction (pcr) is to screen samples for the presence of viruses. for example, remember the recent ebola outbreak? in the us, if a patient is suspected of having clinical symptoms and is at high risk for exposure to ebola virus, one technique to determine if that person is infected with ebola is to send a blood sample for pcr based analysis. in this assay, many copies of specific dna sequences are made in order to cross a detection threshold. each ebola virus is composed of single strand of rna approximately 18,950 nucleotides long enclosed within a cylindrical viral envelope. in some laboratories, the first step might be to incubate samples with the enzyme reverse transcriptase. why might this be? choose all that apply.

a. the polymerase chain reaction is identical to all transcription reactions.

b. dna is often the starting material for pcr so the viral genome is first transcribed into rna.

c. dna is often the starting material for pcr so the viral genome is first reverse transcribed into dna.

d. in pcr, rna primers bind to specific regions of dna not rna so the rna must first be converted to dna.

the polymerase used in pcr is called taq polymerase and is isolated from the hot pool bacteria, thermus aquaticus.
why would human polymerase not be suitable for pcr based methods to determine if infection with ebola had occured? choose all that apply.

a. human polymerase would not recognize viral dna.

b. it is unethical to harvest human polymerase.

c. human polymerase is much larger and more complicated as compared to bacterial polymerase.

d. human polymerase would denature under the conditions of pcr.

e. human polymerase would get infected by ebola dna and not catalyze the reaction.

For the 1st part, the correct answer is option C.  

In a polymerase chain reaction, the amplification of DNA template takes place not RNA. So, prior to going into the process, there is a need to initially convert RNA into DNA with the help of an enzyme reverse transcriptase.  

For the 2nd part, the correct answer is option D.  

The suitable temperature for human DNA polymerase is 37 degrees Celsius, and it gets denatured at greater temperatures. As PCR runs at exceedingly high temperature like 95 degrees Celsius, only Taq DNA polymerase can withstand the temperature. Thus, normal DNA polymerase cannot be utilized in the PCR reactions.  

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.