Biology Final Exam

As an undergraduate student you partake in an undergraduate research project. You decide to repeat the Hershey and Chase experiment, with modifications. You decide to radioactively label the nitrogen of the DNA, rather than the phosphate. Your reasoning is that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. After going through all the work of setting up and performing this experiment, your professor gives you an F! Why did your professor give you a failing grade?

• A) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.
• B) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.
• C) Avery et al. have already concluded that this experiment showed inconclusive results.
• D) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

Phosphorescent bacteria are those which emit light (glow). You decide to mix a living nonphosphorescent strain of bacteria with a heat-killed, phosphorescent strain of bacteria. You then discover that some of the living cells are now phosphorescent. Which observation(s) is the best evidence to conclude that the ability to have phosphoresce is a heritable trait?

• A) The phosphorescence in the living strain is especially bright.
• B) Protein passed from the heat-killed strain to the living strain.
• C) Both DNA and protein passed from the heat-killed strain to the living strain.
• D) Descendants of the living cells are also phosphorescent.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Adenine makes up 12% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be cytosine?

• A) 12%
• B) 24%
• C) 38%
• D) 76%

TOP2A is a gene responsible for the coding of a type of topoisomerase in humans, If TOP2A is mutated and topoisomerase can no longer function, which of the following will mostly likely occur?

• A) No proofreading will occur.
• B) Replication will require a DNA template from another source.
• C) No replication fork will be formed.
• D) The DNA will supercoil.

Tags

NGSS.HS-LS3-2

What enzyme is responsible for joining Okazaki fragments together on the lagging strand during DNA replication?

• A) topoisomerase
• B) DNA polymerase III
• C) DNA ligase
• D) helicase

Xeroderma pigmentosum is a genetic disorder in which those individuals are hypersensitive to sunlight. Being exposed to even small amounts of UV rays from the sun can cause skin cancer. This occurs because their cells are impaired in what way?

• A) They do not recombine homologous chromosomes during meiosis.
• B) They cannot repair thymine dimers – damage to their DNA.
• C) They cannot undergo mitosis.
• D) They cannot replicate DNA.

Tags

NGSS.HS-LS3-2

What would be a likely effect if a cell were unable to produce histone proteins?

• A) Nothing, histone proteins are a non-functioning protein in the cell.
• B) Amplification of other genes would compensate for the lack of histones.
• C) The cell's DNA could not be packed into its nucleus.
• D) Spindle fibers would not form during prophase.

In DNA chromatin, heterochromatin is highly condensed, whereas euchromatin is less compact. Which of the following are true statements in regards to this? [select all that apply]
[ALL OF THEM ARE CORRECT]

• A) Euchromatin is less transcriptionally active than heterochromatin
• B) Genes are typically located in the euchromatin area of chromatin
• C) Heterochromatin is an area of DNA where genes are “turned on”
• D) Telomeres are areas of heterochromatin

The segment of DNA shown in the figure has restriction sites I and II, which create restriction fragments A, B, and C. Which of the gels produced by electrophoresis shown below best represents the separation and identity of these fragments?

• A
• B
• C
• D

How does a bacterial cell protect its own DNA from restriction enzymes?

• A) by reinforcing the bacterial DNA structure with covalent phosphodiester bonds
• B) by using DNA ligase to seal the bacterial DNA into a closed circle
• C) by adding methyl groups to adenines and cytosines
• D) by adding histones to protect the double-stranded DNA