Bio Lecture Ch. 16
Use the figure to answer the following question. Referring to the figure, what bases will be added to the primer as DNA replication proceeds?
5′ A, G, A, C, G, A, C 3′
In an analysis of the nucleotide composition of DNA, which of the following will be found?
A + C = G + T
In the 1950s, when Watson and Crick were working on their model of DNA, which concepts were well accepted by the scientific community? Select all that apply.
Chromosomes are made up of protein and nucleic acid. Genes are located on chromosomes. Chromosomes are found in the nucleus.
What did Rosalind Franklin's famous photo 51 show?
DNA is a helix.
DNA contains the template needed to copy itself, but it has no catalytic activity in cells. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed during DNA replication?
DNA polymerase
Which of the following are DNA-cutting enzymes used in the repair of DNA damage?
NOT ligase
Addition of a nucleotide onto a DNA strand is an endergonic reaction. What provides the energy to drive the reaction?
Release of pyrophosphate from the incoming nucleotide, and then hydrolysis of the pyrophosphate to inorganic phosphate
DNA is a self-replicating molecule. What accounts for this important property of DNA?
The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C.
A hydroxyl is present at the 3' end of the growing DNA strand. What is at the 5' end?
a phosphate group Submit
During mitosis, centromeres separate and chromatids become individual chromosomes during which phase?
anaphase
#7
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What kind of chemical bond is found between paired bases of the DNA double helix?
hydrogen
The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.
hydrogen bonds
During _____, the cell grows and replicates both its organelles and its chromosomes.
interphase
As a result of its involvement in a chemical reaction, an enzyme
is unchanged by the reactants or products.
Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement _____.
permits complementary base pairing
What is the function of the enzyme topoisomerase in DNA replication?
relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix
What is the function of single stranded binding protein?
stabilizing single-stranded DNA at the replication fork
Cytosine makes up 28% of the nucleotides in a sample of DNA from an organism. Approximately, what percentage of the nucleotides in this sample will be thymine?
22%
Use Chargaff's rules to predict the missing values for E. coli, human, and ox DNA. Round your answers to the nearest whole number.
25.3, 24 19.8, 19.8 21, 21, 29
Given a template strand of 3'-ATGCTTGGACA-5' and a partially-made complementary strand containing only 5'-TAC-3', what would be the sequence of the new strand of DNA (including the 5'-TAC-3') if the only additional nucleotides available to DNA polymerase were those containing the bases G, A, and C?
5'-TACGAACC-3'
What materials does DNA polymerase require in order to synthesize a complete strand of DNA? Select all that apply.
All four deoxyribonucleotides triphosphates (containing A, C, T, or G) Single-stranded DNA template 3'-OH end of the new DNA strand Submit
You can use Chargaff's rules to predict the percentage of one or more bases in the DNA of a species if at least one value is known. Source of DNAAdenineGuanineCytosineThymineSea urchin32.8%17.7%17.3%32.1%Salmon29.720.820.429.1Wheat28.121.822.7 Data from several papers by Chargaff: for example, E. Chargaff et al., Composition of the desoxypentose nucleic acids of four genera of sea-urchin, Journal of BiologicalChemistry 195: 155-160 (1952). What is the %T in wheat DNA?
Approximately 28%
What did the structure of DNA's double helix suggest about DNA's properties? Select all that apply.
DNA can change. Errors in copying can result in changes in the DNA sequence that could be inherited by future generations. DNA stores genetic information in the sequence of its bases DNA can be replicated by making complementary copies of each strand
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
Early, flawed DNA models proposed by Watson and Crick and by Linus Pauling correctly described which property of DNA?
DNA is composed of sugars, phosphates, and bases.
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
DNA ligase
A new DNA strand elongates only in the 5' to 3' direction because _____.
DNA polymerase can add nucleotides only to the free 3' end
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
DNA polymerase can join new nucleotides only to the 3′ end of a pre-existing strand, and the strands are antiparallel.
What is the role of DNA polymerase during DNA synthesis?
DNA polymerase is the enzyme that catalyzes the addition of a nucleotide onto the 3' end of a growing DNA strand.
In DNA replication, the resulting daughter molecules contain one strand of the original parental DNA and one new strand. What is the explanation for this phenomenon?
DNA replication is semiconservative
During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?
DNA synthesis can take place only in the 5' to 3' direction. Submit
After the first replication was observed in their experiments testing the nature of DNA replication, Meselson and Stahl could be confident of which of the following conclusions?
Replication is not conservative.
In a healthy eukaryotic cell, the rate of DNA repair is typically equal to the rate of DNA mutation. When the rate of repair lags behind the rate of mutation, what is a possible fate of the cell?
The cell can be transformed into a cancerous cell.
Erwin Chargaff observed that the proportions of adenine (A) and thymine (T) bases were always equal, as were the proportion of guanine (G) and cytosine (C). Chargaff's observation suggests which of the following statements?
The data suggest that A would always pair with T and G would always pair with C in a DNA molecule.
What are the chemical components of a DNA molecule? Select all that apply.
nitrogenous bases sugars phosphate groups
Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?
Hydrolysis of the two phosphate groups (P-Pi) and DNA polymerization are a coupled exergonic reaction.
In the early 1950s, many researchers were racing to describe the structure of DNA using different approaches. Which of the following statements is true?
Jim Watson and Francis Crick built theoretical models, incorporating current knowledge about chemical bonding and X-ray data.
In E. coli, what is the function of DNA polymerase III?
NOT to seal together the broken ends of DNA strands
Tables like the one shown here are useful for organizing sets of data representing a common set of values (in this case, percentages of A, G, C, and T) for a number of different samples (in this case, species). Source of DNAAdenineGuanineCytosineThymineSea urchin32.8%17.7%17.3%32.1%Salmon29.720.820.429.1 Data from several papers by Chargaff: for example, E. Chargaff et al., Composition of the desoxypentose nucleic acids of four genera of sea-urchin, Journal of BiologicalChemistry 195: 155-160 (1952). Does the distribution of bases in sea urchin DNA and salmon DNA follow Chargaff's rules?
Yes, because the %A approximately equals the %T and the %G approximately equals the %C in both species.
If Chargaff's equivalence rule is valid, then hypothetically we could extrapolate this to the combined genomes of all species on Earth (as if there were one huge Earth genome). In other words, the total amount of A in every genome on Earth should equal the total amount of T in every genome on Earth. Likewise, the total amount of G in every genome on Earth should equal the total amount of C in every genome on Earth. Calculate the average percentage for each base in your completed table. Do Chargaff's equivalence rules still hold true when you consider those six species together?
Yes, the average for A approximately equals the average for T, and the average for G approximately equals the average for C. Submit