Bio chapter 12
What is the chronological order of the important discoveries in the structure of DNA? A. Chargaff's ratios of nucleotides -> Franklin makes an X-ray diffraction photo of DNA -> 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. Franklin makes an X-ray diffraction photo of DNA -> Chargaff's ratios of nucleotides -> Watson and Crick identify the double helix D. Chargaff's ratios of nucleotides -> Watson and Crick identify the double helix -> Franklin makes an X-ray diffraction photo of DNA
A
Which of the following include all the others? a. chromosomes b. histones c. nucleosomes d. DNA molecules
A
Which scientists figured out that the shape of a DNA molecule is a double helix? A. Watson and Crick B. Hershey and Chase C. Franklin D. Griffith
A
What is a DNA polymerase?
A principle enzyme that joins individual free floating nucleotides to produce a new strand of DNA.
The Watson and Crick model of DNA. Is a ______ _____, in which two strands are wound around each other.
Double helix
True or false. Watson and Crick discovered that covalent bonds hold base pairs together at the center of a strand of DNA.
False
Which scientist made x-ray diffraction photos of DNA?
Franklin
The tips of chromosomes are known as _________.
Telomeres
During DNA replication, what two processes must occur before the two strands of a DNA molecule can separate?
The DNA must unwind and the hydrogen bonds between the base pairs must be broken.
Describe the structure of a DNA molecule.
The structure of a DNA molecules is a double helix made up of nucleotides. Each DNA strand is formed from the four nitrogenous bases; adenine, guanine, thymine, and cytosine; arranged in different patterns. Adenine and thymine will always be paired together by a weak hydrogen bond, and guanine and cytosine will always be paired together by a weak hydrogen bond. The sequence of the nitrogenous bases will determine the organism.
Rosalind Franklin contributed to the understanding of DNA by...
producing images of DNA molecules using x-rays
Watson and Crick discovered the two strands in DNA...
run in opposite directions
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?
telomerase
Because of base pairing in DNA, the percentage of...
thymine molecules in DNA is about equal to the percentage of adenine molecules
True or false. In eukaryotes, DNA replication proceeds in one direction along the DNA molecule.
False
True or false. The replication of a DNA molecule results in four copies of the same gene
False
What adds base pairs to the DNA strand during DNA replication?
DNA polymerase
How much should the percentages of the four columns of a table of A, C, G, and T add up to?
100%
In both prokaryotes and eukaryotes, how many copies of the chromosome are left after replication?
2
If adenine is 22% and guanine is 28%, then about what percentage would thymine be?
22%
The strand in a DNA molecule is AGCT; therefore, the complimentary strand to the one in Figure 12-7, reading from the bottom up, would be ____
AGCT
What forms a base pair with thymine?
Adenine
In eukaryotes, DNA a. floats freely in the cytoplasm. b. is circular. c. is located in the nucleus. d. is located in the ribosomes.
C
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. radioactive evidence that DNA carried the genetic code c. x-ray diffraction photos of the DNA molecule d. the ratios of the two sets of nucleotide pairs in DNA
C
Which of the following best describes Rosalind Franklin's contribution to our understanding of the structure of DNA? a. 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. b. 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. c. 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. d. 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.
C
DNA replication results in two DNA molecules. a. one with two new strands and the other with two original strands. b. each with two original strands. c. each with two new strands. d. each with one new strand and one original strand.
D
Which of the following is a nucleotide found in DNA? A. Adenine + phosphate group + thymine B. Deoxyribose + phosphate group + polymerase C. Cytosine + phosphate group + guanine D. Deoxyribose + phosphate group + cytosine
D
Which of the following statements correctly describes Chargaff's contribution to the study of DNA? a. Chargaff's experiments conclusively proved that DNA was made of nucleotides, but he could not show that there four types of nitrogenous bases. b. Chargaff hypothesized that DNA was a double helix, but he did not produce the image that proved this fact. c. 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. d. 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
True or false. A DNA strand that had the sequence TACGTT would have a complimentary strand ATCGAT.
False
True or false. DNA is tightly wrapped around nucleosomes.
False
A prokaryotic cell replicates its ___ before it splits to form new cells, so that each new cell can have genetic material.
DNA
DNA replication is carried out by using a series of _______ whose names end with the letters "ase".
Enzymes
True or False. DNA is a nucleic acid made up of nucleosomes joined into long strands or chains by covalent bonds.
False
During DNA replication, a DNA strand that has the bases CTAGGT produces a strand with the bases...
GATCCA
Chromatin contains proteins called _________.
Histones
________ _____ are weak bonds that hold the two strands of DNA together, but also allow the DNA to separate and replicate.
Hydrogen bonds
Eukaryotic DNA has more replication forks than prokaryotic DNA, because it has more starting places, or ______ __ ___________.
Origins of replication
What binds to the prokaryotic chromosome to start DNA replication?
Regulatory proteins
If covalent bonds held the two strands of nucleotides together, the two strands could not easily separate and _________.
Replicate
What are the three main components in a nucleotide?
The base, deoxyribose, and the phosphate group
What structural problem prevents adenine from pairing with guanine?
The bases are both long
If the chromosome lengths are the same, which would be greater in a eukaryote than in a prokaryote?
The number of replication forks on a strand of DNA
Compare and contrast DNA replication in prokaryotes and eukaryotes.
The two processes of DNA replication in prokaryotes and eukaryotes start differently. In prokaryotic DNA replication, the process doesn't start until the regulatory proteins bind to one single point on the chromosome. On the other hand, in eukaryotic DNA replication the process stars in dozens, or even hundreds, of different spots on the chromosome. The rest of the processes are both pretty similar in DNA replication.
If the percentage of guanine in the DNA of a certain species decreased by 5 percent over time, what would you expect to have happened to the percentage of adenine in that DNA?
To increase 5%
True or false. Chargaff contributed to the understanding of DNA by figuring out that the percentages of adenine and thymine were almost equal in any sample of DNA.
True
True or false. The nucleotides within a DNA strand may have different nitrogenous bases, but all have identical sugar molecules.
True
True or false. Watson and Crick used the image of DNA taken by Franklin in their work to figure out the structure of DNA.
True
In both prokaryotes and eukaryotes, DNA replication happens...
before cell division
DNA makes a good molecule for storing information because...
it's bases can be lined together in any order, like the letters of the alphabet can be strung to form different words.
