What happens during the three steps in pcr | Homework Helpers


Chapter 11

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Chapter 19


Chapter 20 & 21



1. Define the 3 stages of cell signaling:

1) Reception –

2) Transduction –

3) Response –

2. Explain the two main types of direct contact (the 1st type has different name for plants/animals; 2nd type is just found in animals – see Fig11.4):

1) Plants:


2) Animals:

3. What is local signaling? What is an example of this?

4. What are hormones? What type of signaling are they involved in?

5. Define: Ligand –

Target cell –

6. Are signal receptors general (will they bind a variety of different signals) or are they very specific?

7. Where are intracellular receptors found?

What types of molecules bind to intracellular receptors? Why must these signals have those characteristics?

8. When a cell surface receptor receives a signal, what generally happens to the receptor? Use the ion-gated receptors as an example.

9. What is a signal transduction pathway?

Having multiple steps in the pathway provides what two things?

What are relay molecules?

Is the actual original signal passed along the pathway?

10. What are second messengers? Where do they function?

The two most common second messengers are:

11. Is the calcium ion concentration higher inside or outside the cell? Why? (What does the cell do to create this gradient?)

12. If the final activated molecule in a signal transduction pathway is a _______________, then the response is turning genes on or off.

13. If hormones are spread all around the body in the bloodstream, then why do only certain cell types respond to certain hormones?


1.Why are viruses generally not considered to be living organisms?

2. What is the general structure of a virus? What is a capsid?

3. Viruses are classified by their type of genetic material. (See Table 19.1)What are the different forms of genetic material that viruses can have?

4. Phages infect what type of host? Draw/depict a simple phage.

5. What does it mean that viruses have a host range?

6. Some viral infections (such as polio) cause permanent cell damage, while others (such as colds) do not. What determines this difference?

7. What does it mean that viruses are obligate intracellular parasites?What things does the host cell provide for the virus to reproduce?

8. Why can’t RNA viruses use the cell’s enzymes to replicate their viral RNA? So what else do these viruses have to bring into the host cell?

9. Why can HIV not be cured? What type of human cells does HIV infect?

What is a retrovirus?

What is reverse transcriptase?

10. What are restriction enzymes and what type of organism has these as defense against viruses?

11. Do antibiotics kill viruses?

12. What is an emerging virus?

Where do emerging viruses come from? (3 main ways viruses “emerge”)


1. What is recombinant DNA?

2. Describe restriction enzymes that are used in molecular techniques.

What are sticky ends?

If two different DNA molecules are cut with the same restriction enzyme, can they connected together?

What enzyme can join two DNA molecules together by forming the phosphodiester bond in the DNA backbone?

3. What is a plasmid? Where do they come from?

4. What is the purpose of gene cloning? Why might we want to do this?

Using Figure 20.5, what are the steps in cloning a gene in a plasmid?

5. Explain how gel electrophoresis separates DNA or proteins by size.

6. What is the purpose of PCR?

Why is Taq polymerase used in PCR? Where does it come from?

What happens during the three steps in PCR?

Do we need much starting DNA to get PCR going? How is this useful in forensics?

7. Plasmids used as cloning vectors often are made with an antibiotic resistance gene. WHY?

8. What is the purpose of cloning an organism? Why might we want to do this?

9. Where are totipotent cells and where are they found?

10. What type of cells are pluripotent and what does this mean?

11. What is the difference between embryonic and adult stem cells?


1. When comparing eukaryotic and prokaryotic genomes, in what three ways are these two major groups different?

1) Genome size:

2) Number of genes:

3) Gene density:

2. How do eukaryotes get more “bang for their buck” with their coding sequences? (See p. 443)

3. What are two ways in which non-coding DNA is useful in eukaryotes?

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