Ch. 12 Take Home Test

Multiple Choice
Identify the choice that best completes the statement or answers the question.

____	1.	In which cells is the accurate transmission of information most important?
a.	nerve cells	
b.	skin cells	
c.	sex cells	
d.	bone cells	

Figure 12–2

____	2.	Figure 12–2 shows the structure of
a.	a DNA molecule.	
b.	an amino acid.	
c.	a RNA molecule.	
d.	a protein.	

____	3.	Which of the following is a nucleotide found in DNA?
a.	adenine + phosphate group + thymine	
b.	cytosine + phosphate group + guanine	
c.	deoxyribose + phosphate group + polymerase	
d.	deoxyribose + phosphate group + cytosine	

____	4.	Because of base pairing in DNA, the percentage of
a.	adenine molecules in DNA is about equal to the percentage of guanine molecules.	
b.	thymine molecules in DNA is about equal to the percentage of adenine molecules	
c.	adenine molecules in DNA is much greater than the percentage of thymine molecules.	
d.	cytosine molecules in DNA is much greater than the percentage of guanine molecules.	

Nitrogenous Bases (%)	
	A	G	T	C	
Human		19.9	29.4		
Chicken	28.8			21.5	
Bacterium
(S. lutea)	2
13.4				
Figure 12–3

____	5.	The table in Figure 12–3 shows the results of measuring the percentages of the four bases in the DNA of several different organisms. Some of the values are missing from the table. Based on Chargaff’s rule, the percentages of guanine bases in chicken DNA should be around
a.	28.8%	
b.	19.9%	
c.	21.5%	
d.	13.4%	

____	6.	DNA makes a good molecule for storing information because
a.	its bases can be joined together in any order, like the letters of the alphabet can be strung to form different words.	
b.	each nucleotide within a DNA strand can give a cell different information, and there are many nucleotides in every cell.	
c.	it can absorb ultraviolet light, so DNA can help protect cells from the  damaging effects of this form of radiation. 	
d.	it is a type of nucleic acid, and most acids are an important part of information storage within cells. 	

____	7.	Which of the following best describes Rosalind Franklin’s contribution to our understanding of the structure of DNA?
a.	She created many models of DNA based on what was known about its properties, and eventually figured out that the structure of DNA is a double helix.	
b.	She purified large amounts of DNA, stretched the fibers so the strands were parallel, and used an X-ray beam to produce an image of the molecule.	
c.	She isolated DNA from many different organisms, and discovered that in every sample, the amount of guanine was almost exactly equal to the amount of cytosine.	
d.	She used radioactive phosphorus and sulfur to produce radioactive viruses, then allowed these viruses to infect bacteria. She found that DNA was the transforming material.	

____	8.	Which of the following statements correctly describes Chargaff’s contribution to the study of DNA?
a.	Chargaff hypothesized that DNA was a double helix, but he did not produce the image that proved this fact. 	
b.	Chargaff’s experiments conclusively proved that DNA was made of nucleotides, but he could not show that there four types of nitrogenous bases.	
c.	Chargaff showed that adenine and thymine were found in equal percentages in DNA, but he did not know this was because of base-pairing.	
d.	Chargaff’s work proved that DNA could be made using radioactive nucleotides, but he did not show that DNA could be transferred from one organism to another. 	

____	9.	In the Hershey-Chase experiment, what happened to the bacteria that had been infected by viruses that had radioactive DNA, and to the bacteria that had been infected with viruses that had been marked with radioactive proteins?
a.	The bacteria infected with viruses that had radioactive DNA had become radioactive. The bacteria that had been infected with viruses marked with radioactive proteins were not radioactive. 	
b.	The bacteria infected with viruses that had radioactive proteins had become radioactive. The bacteria that had been infected with viruses marked with radioactive DNA were not radioactive. 	
c.	The bacteria infected with viruses that had radioactive DNA had become radioactive. The bacteria that had been infected with viruses marked with radioactive proteins had also became radioactive. 	
d.	The bacteria infected with viruses that had radioactive DNA had not become  radioactive. The bacteria that had been infected with viruses marked with radioactive proteins had also not become radioactive. 	

____	10.	Which scientist made x-ray diffraction photos of DNA?
a.	Franklin	
b.	Chargaff	
c.	Watson	
d.	Avery	

____	11.	What is the chronological order of the important discoveries in the structure of DNA?
a.	Franklin makes an X-ray diffraction photo of DNA ® Chargaff’s ratios of nucleotides ® Watson and Crick identify the double helix	
b.	Franklin makes an X-ray diffraction  photo of DNA ® Watson and Crick identify the double helix ®  Chargaff’s ratios of nucleotides	
c.	Chargaff’s ratios of nucleotides ® Watson and Crick identify the double helix ® Franklin makes an X-ray diffraction  photo of DNA	
d.	Chargaff’s ratios of nucleotides ®  Franklin makes an X-ray diffraction  photo of DNA ® Watson and Crick identify the double helix  	

Figure 12–4

____	12.	The table in Figure 12–4 shows the percentages of bases in a DNA sample. How much Thymine should you expect to find in the sample?
a.	22%	
b.	24%	
c.	28%	
d.	44%	

____	13.	Which of the following forms a base pair with thymine?
a.	deoxyribose	
b.	adenine	
c.	guanine	
d.	cytosine	

____	14.	What did Rosalind Franklin contribute to the effort to identify the structure of DNA?
a.	models made of cardboard and wire showing the shape of DNA	
b.	the ratios of the two sets of nucleotide pairs in DNA	
c.	radioactive evidence that DNA carried the genetic code	
d.	x-ray diffraction photos of the DNA molecule	

____	15.	Watson and Crick discovered the two strands in DNA
a.	run in perpendicular directions.	
b.	run in the same direction.	
c.	run in opposite directions.	
d.	run in random directions.	

____	16.	During DNA replication, a DNA strand that has the bases CTAGGT produces a strand with the bases
a.	TCGAAC.	
b.	GATCCA.	
c.	AGCTTG.	
d.	GAUCCA.	

____	17.	What enzyme works to add DNA to ends of chromosomes in rapidly dividing cells such as those found in an embryo, to prevent genes from being lost during replication?
a.	DNA polymerase	
b.	histones	
c.	telomerase	
d.	chromatin	

Figure 12–5

____	18.	In Figure 12–5, what nucleotide is going to be added at point 1, opposite from thymine?
a.	adenine	
b.	thymine	
c.	cytosine	
d.	guanine	

____	19.	Which would be greater in a eukaryote than in a prokaryote?
a.	The percentage of guanine nucleotides.	
b.	The total number of  base pairs in a chromosome.	
c.	The number of replication forks on a strand of DNA.	
d.	The total amount of DNA in a cell.	

____	20.	What binds to the prokaryotic chromosome to start DNA replication?
a.	replication forks	
b.	regulatory proteins	
c.	chromatids	
d.	telomeres	

____	21.	In both prokaryotes and eukaryotes, how many copies of the chromosome are left after replication?
a.	1	
b.	2	
c.	3	
d.	4	

____	22.	In both prokaryotes and eukaryotes, DNA replication happens 
a.	before cell division.	
b.	in the nucleus.	
c.	only to telomeres. 	
d.	around the histones.	

____	23.	
a.		c.		
b.		d.		

Completion
Complete each statement.

	1.	The Watson and Crick model of DNA is a(an) _________________________, in which two strands are wound around each other.

	2.	_________________________ are weak bonds that hold the two strands of DNA together, but also allow the DNA to separate and replicate.

Figure 12–7

	3.	The matching strand to the one in Figure 12–7, reading from the bottom up, would be _________________________.

	4.	If covalent bonds held the two strands of nucleotides together, the two strands could not easily separate and _________________________.

Percentages of Bases	
A	C	T	G	
30				

Figure 12–8

	5.	In figure 12–8, the percentage of guanine would be _________________________.

	6.	Eukaryotic DNA has more replication forks than prokaryotic DNA, because it has more starting places, or _________________________.

Other

Figure 12–12

	1.	Interpret Tables  In Figure 12–12, what do the A, T, G and C stand for?

	2.	Calculate In Figure 12–12, what percentage of thymine would you expect in yeast?

	3.	Calculate Approximately what percentage of adenine would you expect to find in herring in Figure 12–12?

	4.	Predict If the level of thymine in humans were 34 percent instead of 29.4, would you expect the levels of guanine and cytosine to rise or fall, compared to the values in the table in Figure 12–12?

	5.	Relate Cause and Effect In the last row of Figure 12–12, notice that the values adenine and cytosine are very different. If the value for adenine is high, does the value of cytosine have to be low? Explain your answer.

Essay
PICK ONLY ONE ESSAY!

Figure 12–14

	1.	Figure 12–14 shows a short segment of DNA. Explain how the chemical components of a nucleotide give DNA a structure that allows it to hold itself together and yet come apart for replication.

	2.	Compare and contrast DNA replication in prokaryotes and eukaryotes.