Biology Ch. 12
If a mutation occurred in the gene that codes for making DNA polymerase, disabling the ability of this enzyme to be formed properly, then which of the following effects would you expect to occur in a somatic cell?
Base pairing would not occur during DNA replication, and the creation of the daughter strand would be interrupted.
Which of the following build(s) new strands of DNA?
DNA polymerases
Hershey and Chase conducted the experiments separately for radioactively labeled sulfur and radioactively labeled phosphorous, using different phage cultures for each. Which of the following would have occurred if the phage cultures had been combined? Select all that apply.
1) The pellet containing the bacteria would have been radioactive. 2) They would not have been able to conclude which component -- DNA or protein -- was the hereditary material. 3) The liquid containing the phage coats would have been radioactive.
Can you match these biology terms with their definitions? Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.
1. A(n) bacteriophage is a virus that infects bacteria. 2. A chromosomal inversion occurs when a chromosomal fragment breaks off and reattaches to the chromosome in a flipped orientation. 3. The process of DNA replication is semiconservative, meaning that it conserves one parental DNA strand and produces one newly synthesized strand. 4. The enzyme DNA ligase creates a continuous single strand of DNA by bonding the terminal sugar in one DNA fragment to the terminal phosphate in another fragment. 5. A chromosomal translocation occurs when two nonhomologous chromosomes exchange pieces, leaving each with improper gene sequences. 6. The enzyme DNA polymerase synthezises new DNA strands by matching bases on a preexisting template strand with complementary free nucleotides and bonding them together. 7. The enzyme DNA helicase helps unwind the DNA double helix during DNA replication.
Drag the correct element and predicted results to each hypothesis.
32P- Blue (Radioactive DNA in pellet) 35S- Yellow (Radioactive protein in pellet)
Hershey and Chase used _____ to radioactively label the T2 phage's proteins.
35S
Every cell of the body that contains a nucleus has the same exact genetic code in the DNA, yet not all cells are the same. How is a differentiated cell able to make only the proteins it requires for its specific needs?
A cell accesses the portions of the DNA code, that is, genes required to make the proteins that it needs, rather than reading the entire code and making unnecessary proteins.
You wish to demonstrate that DNA replication is semiconservative. You choose to work with bacteria because they have only a single chromosome. You have a very special device that can measure radiation in individual cells. Which radioactive element or compound should you add to the cells prior to division, and what do you expect to see?
Add radioactive phosphate, and expect each cell to contain a radioactive chromosome.
Which of these is responsible for catalyzing the formation of an RNA primer?
D (green box)
The radioactive isotope 32P labels the T2 phage's _____.
DNA
What did Wilkins and Franklin discover?
DNA is a helix with repeating subunits.
Which of the following is not true about the structure of DNA?
DNA is composed of nucleotides with base pairs that are loosely joined together by covalent bonds.
The molecule that seals the gaps between the pieces of DNA in the lagging strand is
DNA ligase
Which statement about DNA replication is FALSE?
DNA ligase adds nucleotides to the lagging strand.
Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?
DNA polymerase can assemble DNA only in the 5' to 3' direction
The copying of a DNA strand is said to be semiconservative. Why is this word used rather than calling it simply duplicated?
Each half of the original DNA strand is kept and used as the template or model strand for the polymerase enzyme to match the base pairs to complement the original side.
Who demonstrated that DNA is the genetic material of the T2 phage?
Hershey and Chase
Which of the result scenarios pictured below accurately represents these findings and supports the conclusion that DNA is the genetic material of bacteriophages? Drag yes or no to each scenario.
NO- 32p radioactive pellet and radioactive solution YES- 32p radioactive pellet and not radioactive solution NO- 32p not radioactive pellet and radioactive solution NO- 35S radioactive pellet and radioactive solution NO- 35S radioactive pellet and not radioactive solution YES- 35S not radioactive pellet and radioactive solution
The synthesis of a new strand begins with the synthesis of a(n) _____.
RNA primer complementary to a preexisting DNA strand
When sequencing DNA, scientists usually determine the sequence of only one of the two strands. Why is this?
Sequencing one strand gives you the complementary sequence to the other strand.
During DNA replication, which nucleotide will bind to an A nucleotide in the parental DNA?
T
What is the complementary strand to the following sequence: ATTGCC . . . ?
TAACGG
Consider the Hershey-Chase experiment using viruses that attack bacteria. Normally the virus coats stay outside the bacteria and only inject DNA. How would the experiment have been affected if the entire virus had entered the cells?
The bacteria would have been radioactive whether the viruses contained radioactive phosphate or sulfur. No conclusions could be drawn about genetic material.
How is it that the entire diversity of life can be spelled out using only four different bases?
The diversity is based on the unique sequence the bases are in.
Which statement about DNA replication is CORRECT?
The leading strand is built continuously, and the lagging strand is built in pieces.
Gene duplication is a type of mutation where one gene is copied to a second location within the genome. The original location still contains the same gene, but now there are two locations with the gene. Evidence shows that this event has happened many times throughout the evolution of life. Why might gene duplication be advantageous to an organism undergoing adaptation?
The second gene can be mutated to new functions without losing the function of the original gene.
In replicating a DNA strand, polymerase makes a mistake and puts adenine across from guanine. If the base-pair mistake is retained, then this could change the shape of the resulting DNA molecule. How might a proofreading enzyme detect this mistake?
The two nucleotides are too large to fit across from each other because of the double-ring base structure. The enzyme will notice the bulge in the DNA structure and attempt to repair the mistake.
How can we best summarize the role of Watson and Crick in discovering the structure of DNA?
They created a key hypothesis for the structure of DNA.
Which of the following would indicate a base pairing mutation in DNA?
a G paired with a T
On the molecular level, what exactly is a mutation?
a change in the sequence of DNA bases
At a very low frequency, the single-ringed pyrimidine cytosine can spontaneously lose its amino group (NH2) and form the base shown. Which nucleotide will this deaminated cytosine pair with?
adenine
How do cigarettes and radiation cause cancer?
by toxic chemicals (in smoke) or radiation that can damage the DNA in cells
How do mutations affect an organism? a) they may cause the development of a disease-causing allele b) they may cause the development of a more beneficial allele c) they, in some cases, may have no noticeable affect
d) all of the above
UV rays can strike two thymine bases sitting beside each other on the same strand, causing them to become linked tightly to one another. This pulls the thymines closer together, altering the spacing of the nucleotides. What kind of error during replication is this likely to cause?
deletion
DNA has the appearance of a _____.
double helix
After DNA replication is completed, _____.
each new DNA double helix consists of one old DNA strand and one new DNA strand
If a mutation in the DNA causes a regulator protein such as myostatin to be ineffective, __________ could explain the result.
enhanced cell growth or replication
Scientists can perform a process called polymerase chain reaction in the lab to copy DNA inside a test tube. This method is part of creating a DNA fingerprint of a suspected criminal. Cells from the suspect's cheek are placed into a tube. They are popped open, and all the proteins and lipids are removed from the solution. The strands of DNA are separated by heating, and polymerase is added to copy the DNA. What necessary component of DNA replication has been left out of this description?
free nucleotides
The complete sequence of DNA in a given organism is called the __________.
genome
The first step in the replication of DNA is catalyzed by _____.
helicase
A female that is planning to become pregnant is concerned about her exposure to environmental mutagens which may have caused DNA mutations. In order for these mutations to become heritable, they must affect the:
her egg cells
Which of the following is most responsible for DNA forming a double helix instead of a single-strand helix structure?
hydrogen bonding between bases
After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found that they contained _____, which demonstrated that _____ is the phage's genetic material.
labeled DNA ... DNA
Short segments of newly synthesized DNA are joined into a continuous strand by _____
ligase
Short segments of newly synthesized DNA are joined into a continuous strand by _____.
ligase
What type of mutation occurs, during replication, when a base pair is mismatched and a wrong base is placed into the daughter strand, for example, when C is paired with C?
nucleotide substitution
DNA is composed of building blocks called _____
nucleotides
What are the monomers of DNA called?
nucleotides
Mutations are changes in the genetic code that can happen because of environmental factors such as toxins, but sometimes they also happen randomly. Which of the following describes the error rate of mistakes that occur in the replication of DNA under normal circumstances for a given DNA strand?
one mistake per every 100 million base pairs matched
This is an image of a _____.
phage
The action of helicase creates _____.
replication forks and replication bubbles
The lytic cycle of bacteriophage infection ends with the _____.
rupture of the bacterium
Natural selection can enhance the frequency of beneficial mutations in a population. In which type of cells must the mutations occur to have an effect on future generations?
sex cells/gametes
DNA replication occurs at an unbelievably fast rate. Once replication is complete, we can expect to find a _____ number of mistakes.
small
A thymine base is replaced by a cytosine in a DNA molecule. What type of mutation is this?
substitution
What forms the backbone of a DNA molecule?
sugar rings and phosphates
An old DNA strand is used as a _____ for the assembly of a new DNA strand.
template
As a result of the lytic cycle, _____.
the host cell's DNA is destroyed
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
Which type of mutation affects the sequence of multiple nucleotides at one time and occurs between chromosomes rather than only in the double helix of one chromosome?
translocation mutations
What is the final result of DNA replication of one chromosome?
two new strands, each bound to a parent strand
The pointer is indicating the _____.
viral protein coat
