Materials Included In Kit

Additional Materials Required

Safety Precautions

The materials used in this activity are considered nonhazardous. Please follow all normal classroom safety guidelines.

Lab Hints

• Enough materials are provided in this kit for 8 groups of students. The Baseline Activity can reasonably be completed in one 50-minute class period. The research may be completed outside of class. The poster session or other presentation may be completed in a second class period.
• With enough introduction and experience with karyotypes this activity may be completed as homework.
• Use prepared microscope slides of chromosome spreads to show the size. Flinn Scientific carries several types.
• Have students prepare their own chromosome spreads using the large chromosomes of Drosophila virilis. Please contact Flinn Scientific and request the digital publication.

Further Extensions

Opportunities for Inquiry 

Research aneuploidy and translocation in breast cancer, bladder cancer, prostate cancer or another cancer. Locate one or more karyotypes online for these cancers. Prepare a miniposter or other presentation on the cancer of choice.

Concepts and Curriculum Framework for AP^® Biology 

Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis.

Enduring Understandings
2A3: Organisms must exchange matter with the environment to grow, reproduce, and maintain organization.
2B1: Cell membranes are selectively permeable due to their structure.
2B2: Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes.
2D1: All biological systems from cells and organisms to populations, communities, and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.

Big Idea 3: Living systems store, retrieve, transmit and respond to information essential to life processes.

Enduring Understandings
3A1: DNA, and in some cases RNA, is the primary source of heritable information.
3A2: In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization.
3A3: The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring.
3C2: Biological systems have multiple processes that increase genetic variation.

Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties.

Enduring Understandings
4A4: Organisms exhibit complex properties due to interactions between their constituent parts.
4A6: Interactions among living systems and with their environment result in the movement of matter and energy.

Learning Objectives

• The student can make predictions about natural phenomena occurring during the cell cycle (3A2 & SP 6.4).
• The student can describe the events that occur in the cell cycle (3A2 & SP 1.2).
• The student is able to construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization (3A2 & SP 6.2).
• The student is able to represent the connection between meiosis and increased genetic diversity necessary for evolution (3A2 & SP 7.1).
• The student is able to evaluate evidence provided by data sets to support the claim that heritable information is passed from one generation to another generation through mitosis, or meiosis followed by fertilization (3A2 & SP 5.3).
• The student is able to construct a representation that connects the process of meiosis to the passage of traits from parent to offspring (3A3 & SP 1.1, SP 7.2).
• The student is able to construct an explanation of the multiple processes that increase variation within a population (3C2 & SP 6.2).

Science Practices
1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain.
1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain.
5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question.
6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices.
6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models.
7.1 The student can connect phenomena and models across spatial and temporal scales.
7.2 The student can connect concepts in and across domains to generalize or extrapolate in and/or across enduring understandings and/or big ideas.

Answers to Questions

• Karyotype Sheet 1 is a normal female. There are 46 chromosomes present.
• Karyotype Sheet 2 is a chronic myeloid leukemia karyotype. CML is typically a (9;22) translocation with one extra-long chromosome 9 and one very short chromosome 22, the Philadelphia chromosome t(9;22)(q34;q11.2). The remainder of the karyotype is that of a normal female. There are 46 chromosomes present.
• Karyotype Sheet 3 is a normal male. There are 46 chromosomes present.
• Karyotype Sheet 4 is a mantle cell lymphoma karyotype. MCL is typically an (11;14) translocation with the bottom of chromosome 11 switching with the bottom of chromosome 14 t(11;14)(q13;q32). The remainder of the karyotype is that of a normal male. There are 46 chromosomes present.
• Karyotype Sheet 5 is a HeLa karyotype. HeLa is seen as aneuploid female karyotype with chromosomes 3 and Y absent, chromosome 22 only has one copy present, chromosomes 4, 8, 12, 19 and X have 2 copies present, chromosomes 1, 2, 7, 11, 13, 14, 18, 20 and 21 have three copies present, chromosomes 5, 9, 10, 15, 16 and 17 have four copies present, and chromosome 6 has five copies present for a total of 67 chromosomes. The HeLa cell line has changed over the last 60+ years. There are so many different variations in chromosome number that the cell line chromosome number is noted as a subscript. For example, the karyotype used for this activity is HeLa₆₇. HeLa is a cell infected by HPV-18.
• Karyotype Sheet 6 is an anaplastic large-cell lymphoma karyotype. ALCL is a (2;5) translocation with the top bands of 2 attaching to the bottom of 5 t(2;5)(p23;q35). The remainder of the karyotype is that of a normal male. There are 46 chromosomes present.
• Karyotype Sheet 7 is a Burkitt’s lymphoma karyotype. Burkitt’s lymphoma can be an (8;14) translocation with the bottom bands of 8 attaching to the bottom of 14 t(8;14)(q24;q32). The remainder of the karyotype is that of a normal female. There are 46 chromosomes present.
• Karyotype Sheet 8 is a follicular lymphoma karyotype. Follicular lymphoma can be a (14;18) translocation with the bottom bands of 18 attaching to the bottom of 14 t(14;18)(q32;q21). The remainder of the karyotype is that of a normal female. There are 46 chromosomes present.
• Karyotype Sheet 9 is a synovial sarcoma karyotype. Synovial sarcoma is a reciprocal (X;18) translocation with the bottom of 18 and the top of the X chromosome switching places t(x;18)(p11.2;q11.2). The remainder of the karyotype is that of a normal female. There are 46 chromosomes present.
• Karyotype Sheet 10 is a dermatofibrosarcoma protuberans karyotype. DFSP is a rare tumor. It is a (17;22) translocation in which the two chromosomes also fuse into a circle t(17;22)(q22;q13). The remainder of the karyotype is that of a normal male. There are 45 chromosomes present.
• Karyotype Sheet 11 is a Ewing’s sarcoma karyotype. Ewing’s sarcoma in 90 percent of cases is a (11;22) translocation with the bottom of 22 attaching to the bottom of 11 t(11;22)(q24;q12). The remainder of the karyotype is that of a normal male. There are 46 chromosomes present.

Teacher Handouts

11120_Teacher1.pdf

References

AP Biology Investigative Labs: An Inquiry-Based Approach. College Entrance Examination Board: New York, 2012.

Biology: Lab Manual; College Entrance Examination Board: New York, 2001.

HPV cancer. Accessed Feb. 2012. http://www.cdc.gov/hpv/cancer.html

Karyotype image research. Accessed Feb. 2012. www.medscape.com and elsevierimages.com

Lucey, B. P., Nelson-Rees, W. A., and Hutchins, G. M. “Henrietta Lacks, HeLa Cells, and Cell Culture Contamination”; Archives of Pathology & Laboratory Medicine; College of American Pathologists, Sept. 2009, Vol 133, pp 1463–1467.

Nambiar, M., Kari, V., Raghaven, S. “Chromosomeal Translocations in Cancer”; Reviews on Cancer, Biochimica et Biophysica Acta (BBA) Dec. 2008, Vol 1786, Issue 2, pp 139–152.

Introduction

Cell division is a tightly controlled process. What happens when infection by a virus or radiation causes the controls to fail? What are the consequences of uncontrolled cell division?

Concepts

• Aneuploidy
• Apoptosis
• Cell cycle
• Chromosome structure errors
• Cell cycle checkpoints
• Karyotype
• Cancer
• Centromere location
• Mitosis

Background

Cell division occurs due to a complex set of cell signals. Various cell signals cause the transcription of specific genes, the generation of new organelles, and the general functioning of the cell. Built into cell division are three checkpoints. These three eukaryote checkpoints are points at which the cell division process proceeds, halts for repairs or triggers cell death. Cell death is called apoptosis. The checkpoints regulating cell division have been evolutionarily conserved among animals. This means the checkpoint mechanisms in fruit flies are very similar to those in our own bodies. As a result, scientists are able to use less complex organisms to study the cell signaling pathways involved in cell division.

At each checkpoint the cell determines whether or not all of the components and conditions have been met for cell division to proceed. The three checkpoints in eukaryotes are called the G1, the G2, and the M-spindle checkpoints. If the cell is halted at the G1 checkpoint the cell never progresses to the synthesis phase of interphase in which the DNA is replicated. At the G2 checkpoint any problems in the replicated DNA trigger the cell to halt in G2 until either repairs are made or apoptosis is prompted. The final mechanism for controlling cell division is the M-spindle checkpoint, which occurs in metaphase of mitosis. This checkpoint requires the kinetochore of each chromosome to be connected to the microtubules of the mitotic spindle. If an error is detected, mitosis is halted until repairs are made. If at any of the checkpoints repairs are not possible or take too long, apoptosis is triggered and the cell dies.

Cancer is rapid, uncontrolled growth of cells. Problems with the three checkpoints are a common way for cancer to start. A problem can arise when molecules that promote cell division are expressed more than usual. An excess of promoter molecules will overwhelm the checkpoint cell-signaling pathway and cause cell division to continue unchecked even if significant errors are present. Conversely, molecules that hinder cell division may be repressed or tagged for destruction. Again, the lack of molecules from the cell-signaling pathway that would stop a cell from dividing causes the cell to replicate even though it contains errors. Pathologists who study cancer by examining at the chromosomes of a cancer cell are able to identify many of these changes due to errors in cell-signaling pathways.

Infection by certain viruses, a physical source, such as UV damage, or a genetic defect that occurred during the rapid replication of fetal development are all potential sources of faulty checkpoints. One virus with numerous subtypes that can lead to checkpoint errors and therefore cancer is the human papillomavirus (HPV). Subtype HPV-18 is particularly aggressive. Within the 8000-base-pair DNA genome of HPV-18 is the code for two checkpoint-interfering proteins. Like many viruses, HPV inserts itself into the chromosome of a host cell, causing the viral proteins to be transcribed along with host proteins. The two viral proteins both interfere with the G1 checkpoint. One of the two proteins targets a cell-division repressor molecule and tags the repressor molecule for destruction by the cell. The second viral protein acts by binding to the protein that traps a host protein. This particular host protein is a cell-division promoter. By binding to the promoter the virus causes the cell to move through the G1 checkpoint without correction. Recently a vaccine has been developed to guard against some of these cancer-causing HPV subtypes.

Once the cell is off track, multiple chromosome mutations may build up, including aneuploidy. Aneuploidy is an abnormal number of chromosomes. Scientists stain and visualize chromosomes using a light microscope. Pathologists routinely test biopsy samples in this manner. A typical cell will have 46 chromosomes—any more or less is aneuploidy. Aneuploidy is just one difference that is visible in a cancer cell. By capturing an image of chromosomes in metaphase, the chromosomes can be counted and matched. This is called a karyotype.

Each pair of homologous chromosomes is easily distinguished from other chromosomes by differences in length, in the position of the centromere, and by the pattern of bands created using special stains. The centromere is always located in one of three possible positions in human chromosomes (see Table 1). If the centromere is in the center of the chromosome it is called metacentric. If the centromere is located near one end of the chromosome it is called acrocentric. The third centromere position may be between the center and the end of the chromosome—this position is called submetacentric.

If a large structural change or error occurs in a chromosome, the banding pattern may be altered. Structural errors occur when part of a chromosome is missing or not located in its correct position (see Figure 1). The four types of structural errors are inversions, deletions, duplications and translocations. Inversions involve a section of chromosome breaking off and then reattaching to the same chromosome upside down. If a section of a chromosome is completely absent it is called a deletion. Duplications occur when a section of the chromosome is repeated. Translocations arise when part of one chromosome breaks off and attaches to another chromosome. Chronic myeloid leukemia (CML) is just one type of cancer caused by a translocation error. The translocation in CML involves chromosomes 9 and 22. Since the odd karyotype was found in the early days of karyotyping the true nature was not known. Consequently the truncated chromosome 22 was called the Philadelphia chromosome in honor of the city in which it was discovered. Actual karyotypes have chromosomes that are bent and twisted. For simplicity sake idealized chromosomes called ideograms are used in this kit. See Figure 2 for a schematic of normal chromosomes. All of the ideograms included in the kit involve aneuploidy or translocations.

Experiment Overview

After comparing normal karyotypes to two known cancerous karyotypes, two unknown karyotypes will be evaluated and assessed.

Materials

Safety Precautions

The materials used in this activity are considered nonhazardous. Please follow all normal classroom safety guidelines.

Procedure

Baseline Activity

1. Count the chromosomes on the Karyotype Sheet to determine the total number of chromosomes.
2. Carefully cut out the individual chromosomes on the Karyotype Sheet.
3. Arrange the chromosomes in order of decreasing size, from largest to smallest on a sheet of paper.
4. Use the size, centromere location and banding pattern on each chromosome to match homologous pairs of chromosomes. Note: Refer to Table 1 and Figure 2 for the centromere locations on human chromosomes.
5. Tape or glue the chromosomes to a sheet of paper and label it.
6. Compare each unknown karyotype with the normal karyotypes. Write a summary of the similarities and differences between the karyotypes. Make sure to note the gender of the person and the type of error.
7. Each of the karyotypes included is of a known chromosomal error that causes cancer. Research one of these errors or one of the many other cancer types caused by a chromosomal abnormality. Share your findings with the class.