1.
What did Wilkins and Franklin discover?
Correct Answer
A. DNA is a helix with repeating subunits.
Explanation
Wilkins and Franklin discovered that DNA is a helix with repeating subunits.
2.
How can we best summarize the role of Watson and Crick in discovering the structure of DNA?
Correct Answer
C. They created a key hypothesis for the structure of DNA.
Explanation
Watson and Crick's role in discovering the structure of DNA can be best summarized by stating that they created a key hypothesis for the structure of DNA. This implies that they proposed a theoretical model or explanation for the structure of DNA based on their observations and understanding. While it is true that they made key observations in the lab and performed experiments, these activities were part of the process of developing their hypothesis. The statement that they provided the final proof of the structure of DNA is not accurate, as their hypothesis required further validation and confirmation by subsequent research and experiments.
3.
What forms the backbone of a DNA molecule?
Correct Answer
F. Sugar rings and pHospHates
Explanation
The backbone of a DNA molecule is formed by sugar rings and phosphates. These two components alternate to create a strong and stable structure. The sugar rings provide the framework for the DNA molecule, while the phosphates link the sugar rings together. This backbone is essential for the stability and integrity of the DNA molecule, allowing it to store and transmit genetic information accurately. Nitrogenous bases, on the other hand, are attached to the sugar rings and play a crucial role in encoding the genetic information within the DNA molecule.
4.
Look at the structures of adenine and cytosine. Why can't adenine bind to cytosine like it binds to thymine?
Correct Answer
B. The partial charges are not opposites, so no hydrogen bonds can form.
Explanation
The partial charges in adenine and cytosine are not opposite to each other, meaning they do not have the necessary polarity to form hydrogen bonds. Hydrogen bonds are formed between a hydrogen atom with a partial positive charge and an atom with a partial negative charge. Since the partial charges in adenine and cytosine do not align in a way that allows hydrogen bonding, adenine cannot bind to cytosine in the same way it binds to thymine.
5.
What is the complementary strand to the following sequence? ATTGCC
Correct Answer
C. TAACGG
Explanation
The complementary strand to the given sequence "ATTGCC" is "TAACGG". In DNA, the base pairs are A-T and G-C. So, for each base in the original sequence, we need to find its complementary base. In this case, A pairs with T, T pairs with A, G pairs with C, and C pairs with G. Therefore, the complementary strand is "TAACGG".
6.
When sequencing DNA, scientists usually only determine the sequence of one of the two strands. Why is this?
Correct Answer
D. Sequencing one strand gives you the complementary sequence to the other strand.
Explanation
When sequencing DNA, scientists usually only determine the sequence of one of the two strands because sequencing one strand gives them the complementary sequence to the other strand. Since DNA strands are complementary to each other, knowing the sequence of one strand allows scientists to determine the sequence of the other strand without directly sequencing it. This saves time and resources in the sequencing process.
7.
How is it that the entire diversity of life can be spelled out using only four different bases?
Correct Answer
E. The diversity is based on the unique sequence the bases are in.
Explanation
The diversity of life is based on the unique sequence of bases in DNA. Each DNA molecule consists of a specific sequence of four different bases: adenine (A), thymine (T), cytosine (C), and guanine (G). The arrangement of these bases in the DNA molecule determines the genetic code and the instructions for building and functioning of organisms. The unique sequence of bases allows for the vast diversity of life, as different sequences result in different genes and traits. Therefore, the diversity of life can be spelled out using only four different bases because the unique sequence of these bases is responsible for the diversity.
8.
On the molecular level, what exactly is a mutation?
Correct Answer
D. A change in the sequence of DNA bases
Explanation
A mutation refers to a change in the sequence of DNA bases. This means that there is an alteration in the order of the building blocks (adenine, guanine, cytosine, and thymine) that make up the DNA molecule. This change can occur due to various factors such as errors during DNA replication or exposure to certain chemicals or radiation. Mutations can have different effects, ranging from no impact to causing genetic disorders or contributing to the development of diseases like cancer.
9.
Scientists can perform a process called polymerase chain reaction in the lab in order 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?
Correct Answer
D. Free nucleotides
Explanation
The necessary component of DNA replication that has been left out of this description is free nucleotides. During DNA replication, free nucleotides are used to build the complementary strands of DNA by pairing with the existing nucleotides on the template strand. These free nucleotides are the building blocks of DNA and are essential for the replication process to occur accurately. Without the addition of free nucleotides, the DNA cannot be copied successfully.
10.
What is the final result of DNA replication of one chromosome?
Correct Answer
F. Two new strands, each bound to a parent strand
Explanation
During DNA replication, the double-stranded DNA molecule unwinds and separates into two individual strands. Each of these strands serves as a template for the synthesis of a new complementary strand. As a result, two new strands are formed, with each new strand being bound to its respective parent strand. This process ensures that the genetic information is accurately replicated and passed on to the daughter cells.
11.
You wish to prove that DNA replication is semi-conservative. You choose to work with bacteria because they only have 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?
Correct Answer
D. Add radioactive pHospHate and expect each cell to contain a radioactive chromosome.
Explanation
The correct answer is to add radioactive phosphate and expect each cell to contain a radioactive chromosome. This is because DNA replication involves the synthesis of new DNA strands using nucleotides, which contain phosphate groups. By adding radioactive phosphate, it will be incorporated into the newly synthesized DNA strands during replication. Since each cell undergoes DNA replication and receives a copy of the chromosome, each cell will contain a radioactive chromosome. This supports the idea of semi-conservative DNA replication, where each newly formed DNA molecule consists of one original strand and one newly synthesized strand.
12.
How do cigarettes and radiation cause cancer?
Correct Answer
E. By forcing mistakes during replication
Explanation
Cigarettes and radiation cause cancer by forcing mistakes during replication. When DNA replicates, errors can occur naturally, but cigarettes and radiation increase the likelihood of these errors happening. The chemicals in cigarettes and the radiation can damage the DNA structure, leading to replication errors. These mistakes can result in mutations that can disrupt normal cell function and potentially lead to the development of cancer.
13.
Where in the cell cycle would a checkpoint activate if a mistake were made during replication?
Correct Answer
E. G2 pHase
Explanation
During the G2 phase of the cell cycle, a checkpoint would activate if a mistake were made during replication. This is because the G2 phase is the last phase before the cell enters into the mitotic phase (M phase), where the cell divides. The checkpoint in the G2 phase ensures that the DNA has been accurately replicated and any errors are corrected before proceeding to the next phase.