A
B
C
D
E
100
Scientists believe that RNA may have been the first genetic material on Earth, but DNA eventually became the primary genetic material in most organisms.
Which of the following best explains why DNA replaced RNA as the main genetic material?
a.DNA can leave the nucleus, but RNA cannot.
b.DNA is more stable and more easily repaired than RNA.
c.DNA contains uracil, which makes replication easier.
d.RNA is double-stranded, making it too complex for cells to use.
b.DNA is more stable and more easily repaired than RNA.
100
What is the most direct consequence of a cell bypassing a checkpoint in the cell cycle?
a.The cell uses more energy than it needs for replication.
b.The cell enters quiescence (G0) and cannot divide.
c.The cell continues to grow and divide indefinitely.
d.The cell returns to the G0 phase to correct its mutation
c.The cell continues to grow and divide indefinitely.
100
Which components make up the structural backbone of a DNA molecule?
Select TWO correct answers.
a.Deoxyribose sugars
b.Ribose sugars
c.Pyrimidine bases
d.Phosphate groups
e.Adenine bases
A and D
100
A student examines an onion root tip under a microscope and sees that the chromosomes have separated and are moving toward opposite ends of the cell.
Which phase of mitosis is the student observing?
a.Anaphase
b.Prophase
c.Metaphase
d.Telophase
a.Anaphase
100
Scientists studied cells that had a mutation in the RB gene, which normally helps control the checkpoint between the G1 and S phases of the cell cycle. Over time, a mass of cells began to form.
Which term best describes the mass of cells observed?
a.Organelle
b.Tumor
c.Embryo
d.Blood clot
Tumor
200
During which stage of the cell cycle does DNA replication occur?
S phase
200
Male deer shed their antlers each year. New antlers then grow back rapidly, requiring the production of many new cells.
Which process is responsible for producing these new cells?
a.Mitosis
b.Photosynthesis
c.Diffusion
d.Active transport
a.Mitosis
200
Scientists can compare DNA from different species to study how organisms are related. This comparison is possible because all living things use the same genetic code.
Which component of DNA is universal among all living things?
a.Nitrogenous bases in nucleotides
b.Ribose sugar in nucleotides
c.Number of chromosomes in the cell
d.Length of the DNA molecule
a.Nitrogenous bases in nucleotides
200
Some multicellular organisms increase in size due to cell replication, and some single-celled organisms reproduce without combining genetic material from another cell. In both cases, cells copy their genetic material before division.
Which statement best explains the importance of this process?
a.It produces new cells with identical DNA, supporting growth and asexual reproduction.
b.It produces new cells with unique DNA combinations, increasing genetic variation.
c.It produces new cells with half the DNA, reducing genetic material in each generation.
d.It produces new cells without copying DNA, allowing division without transferring genetic information.
a.It produces new cells with identical DNA, supporting growth and asexual reproduction.
200
Which table correctly compares mitosis and cytokinesis? 
D
300
Students create a model of DNA using licorice ropes, gummy candies, and marshmallows. The marshmallows connect pairs of gummy candies at the center of the model.
What do the marshmallows represent in the DNA model?
a.Sugar molecules
b.Phosphate groups
c.Nitrogen bases
d.Hydrogen bonds
d.Hydrogen bonds
300
A partial DNA sequence is shown. Which bases would complete the complementary sequence of DNA?
A C T G A C T
T G A C T G A
300
The image shows a cellular process.
What is the significance of the process shown in the image?
a.It allows the cell to produce proteins by copying DNA into RNA and translating it into proteins.
b.It provides energy for the cell by breaking down nucleotides and creating ATP.
c.It ensures that each new cell receives an identical copy of the genetic material.
d.It controls which genes are turned on or off in the cell.
c.It ensures that each new cell receives an identical copy of the genetic material.
300
A segment of a DNA molecule has the following sequence on one strand.
5′–A T G C C A T–3′
Which sequence represents the complementary strand of DNA?
a. 3′–A T G C C A T–5′
b. 5′–T A C G G T A–3′
c. 3′–T A C G G T A–5′
d. 5′–A U G C C A U–3′
c. 3′–T A C G G T A–5′
300
A scientist is studying the platypus, Ornithorhynchus anatinus, which has 52 chromosomes in each somatic cell.
After one complete cell cycle, how many chromosomes will be present in each daughter somatic cell?
52
400
Doctors are studying abnormal tissue growth in a patient’s colon. Biopsy results show that many of the cells are replicating rapidly and appear to have mutations in genes that regulate the G1 checkpoint of the cell cycle. The doctors determine that these cells are no longer responding to internal regulatory signals.
Which conclusion best explains how these cellular changes relate to disease development?
a.The cells are producing additional proteins to repair DNA damage, which can indicate a genetic disorder.
b.The checkpoint failure allows uncontrolled division, which can lead to cancer.
c.The G1 checkpoint triggers the cells to enter apoptosis prematurely, which contributes to tissue degeneration.
d.The tissue is growing rapidly due to changes in the patient’s immune system, which may indicate an autoimmune disease.
b.The checkpoint failure allows uncontrolled division, which can lead to cancer.
400
Which statement best describes how the work of key scientists contributed to the accepted model of DNA structure?
a.Rosalind Franklin generated data on DNA independently, while James Watson and Francis Crick developed a model of DNA without using her findings.
b.Rosalind Franklin, James Watson, and Francis Crick worked together in the same laboratory to directly observe DNA with a light microscope and confirm its structure through shared experimentation.
c.Rosalind Franklin generated X-ray diffraction images that revealed DNA’s helical pattern, and James Watson and Francis Crick used those data to construct the double-helix model.
d.Rosalind Franklin studied DNA’s structure, while James Watson and Francis Crick concluded that DNA was primarily composed of proteins arranged in a repeating structural pattern.
c.Rosalind Franklin generated X-ray diffraction images that revealed DNA’s helical pattern, and James Watson and Francis Crick used those data to construct the double-helix model.
400
The image shows the variation in shell color of Texas armadillos. Some armadillos have dark shells, while others have light shells.
Complete the sentence by selecting the correct answer from each drop-down menu.
Variations occur because the (number, sequence, location) of (phosphate groups, hydrogen bonds, nitrogenous bases) determines the color of a Texas armadillo’s shell and influences which proteins the cell can produce.
Sequence
nitrogenous bases
400
A scientist measured the amount of DNA in one cell type over time. The results are shown in the graph below.
Which conclusion about DNA replication is supported by the graph?
a.DNA replication occurs after cytokinesis in cells.
b.DNA replication only occurs in rapidly dividing cells.
c.DNA replication reduces the total amount of DNA in a cell.
d.DNA replication occurs in cells before division.
d.DNA replication occurs in cells before division.
400
Which statement best describes how a nitrogen (nitrogenous) base is connected in a DNA nucleotide?
a.The nitrogen base attaches to both the sugar and the phosphate.
b.The nitrogen base attaches directly to the phosphate.
c.The nitrogen base attaches directly to the sugar.
d.The nitrogen base floats freely and does not attach to any part of the nucleotide.
c.The nitrogen base attaches directly to the sugar.
500
A teacher provides a diagram of a plant cell in various stages of mitosis.
Which sequence lists the stages of mitosis in the correct order?
a.A, D, C, B
b.B, C, D, A
c.A, B, C, D
d.C, D, A, B
b.B, C, D, A
500
Scientists study two groups of human cells to investigate how cyclin-dependent kinase (CDK) activity affects cell cycle progression. In healthy cells, DNA damage inactivates CDKs and stops the cell cycle at checkpoints. After 24 hours, researchers measure CDK activity and count the number of cells in mitosis. The results are shown below.
Based on the data, which conclusion best explains how the mutant cell line could contribute to cancer development?
a.High CDK activity increases DNA repair efficiency and produces a greater number of healthy daughter cells.
b.Elevated mitotic counts demonstrate stronger apoptosis signals and improved regulation of damaged cells.
c.Reduced checkpoint control causes cells to remain in interphase and decreases the overall rate of tissue growth.
d.Ongoing CDK activity permits cells to pass checkpoints without repair and results in excessive cell division.
d.Ongoing CDK activity permits cells to pass checkpoints without repair and results in excessive cell division.
500
In normal tissues, damaged or abnormal cells are removed through apoptosis, a process in which cells self destruct to prevent harm to the body. In some cases, mutations in genes that regulate the cell cycle prevent signals that detect cellular damage from triggering apoptosis. As a result, damaged cells continue dividing instead of being eliminated.
Which statement best explains how this disruption can contribute to the development of cancer?
a.Damaged cells continue dividing and use excess energy, which can increase the number of cells in the tissue.
b.Damaged cells fail to undergo apoptosis and continue dividing, which allows mutations to accumulate.
c.Damaged cells stop responding to growth signals and remain inactive, which decreases the overall tissue growth.
d.Damaged cells replicate DNA less efficiently, which slows cell turnover and reduces tissue development.
b.Damaged cells fail to undergo apoptosis and continue dividing, which allows mutations to accumulate.
500
Students reviewed a table describing key events that occur during the cell cycle. Use the table to match each description with the correct phase.
Select the correct answer in each row.
M
I
M
I
I