Chapter 4 Homework
If nucleotides from the DNA of a human were quantified and 30 percent of them contained the base adenine, what percentage of them would contain the base guanine?
20 percent
If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching strand?
3'-TAAACG-5'
RNA always consists of a single strand of nucleotides, but sometimes the single strand can fold over and base-pair with itself in short regions. Help complete this model by filling in the missing nucleotides with the correct 5'-3' orientation. RNA contains uracil (U) in place of thymine (T).
3) A-U (5 ......U-A 5) C-G (3
Identify the four bases in this RNA strand. What is the correct order of the base sequences, starting at the 5' end?
5'-UAGC-3'
If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?
75
How does the structure of DNA allow it to be copied?
After separating the strands of a DNA double helix, each template strand can be copied to make two identical DNA molecules.
How do the secondary structures of DNA and RNA differ?
DNA consists of two nucleotide strands, and RNA consists of one that often folds on itself.
Several students have been practicing drawing their models of nucleotides. Whose model do you think is most consistent with the actual chemical structure of nucleotides?
Jamals
Which chemical structure is represented by the yellow shape in the model?
PO4
Which symbol is generally used to represent a sugar in simple models of nucleotides?
Pentagon
Which of the following correctly describes nucleic acid synthesis?
Polymerization of nucleic acids occurs by the formation of phosphodiester bonds.
If 14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled?
RNA
What is the difference between a ribonucleotide and a deoxyribonucleotide?
Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
A student has drawn an enlarged portion of a DNA "ladder" model to show two of the nucleotides in greater detail (in the same orientation as they would occur in the ladder model). Which two nucleotides did the student draw?
T,G The orange circled one
Interpret the model. Drag "True" or "False" to the end of each statement.
The 3' and 5' carbon labels are in the correct locations in the model. = True This model shows six nucleotides bonded together. = False This model shows that there is more than one kind of nitrogenous base. = True This model represents two nucleic acids bonded together. = False This model shows that phosphate groups bond to nitrogenous bases. = False This model shows that phosphate groups bond to sugars. = True This model shows that there is more than one kind of sugar. = False
Which model correctly explains the meaning of 3' and 5' in nucleic acids?
The 5' carbon is bonded to the phosphate group and the 3' carbon is bonded to an OH group.
Interpret the model. Drag "True" or "False" to the end of each statement.
The arrowheads represent the 3' ends of the strands. = True The vertical lines represent sugar-phosphate backbones containing covalent bonds. = True This model represents RNA. = False The horizontal lines represent covalent bonds. = False The arrowheads represent the phosphate group at the end of the strand. = False The nitrogenous bases are all paired correctly. = False
Both DNA and RNA _____.
are information-containing molecules
The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA _____.
contains one less oxygen atom
Which of the following are pyrimidine nitrogenous bases?
cytosine and uracil
Identify three possible components of a DNA nucleotide.
deoxyribose, phosphate group, thymine
In eukaryotic cells DNA has the appearance of a _____.
double helix
One of the primary functions of RNA molecules is to _____.
function in the synthesis of proteins
Which of the following are purine nitrogenous bases?
guanine and adenine
The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.
hydrogen bonds
If cells are grown in a medium containing radioactive 32P-labeled phosphate, which of these molecules will be labeled?
nucleic acids
DNA is composed of building blocks called _____.
nucleotides
Nucleic acids are polymers made up of which of the following monomers?
nucleotides
A nucleotide is composed of a(n) _____.
phosphate group, a nitrogen-containing base, and a five-carbon sugar
In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
thymine ... cytosine
