Bio 1010 Exam 3 practice questions

Following meiosis I, the daughter cells are ________; following meiosis II, the daughter cells are ________; and following mitosis, the daughter cells are ________.

haploid; haploid; diploid The first meiotic division reduces the chromosome number, while the second division maintains chromosome number. Thus, daughter cells after meiosis I are haploid, and after meiosis II are still haploid. Mitosis maintains the chromosome number, so the daughter cells are diploid following mitosis.

Chromosomes that occur in pairs and code for the same traits are called ________ chromosomes; these do not include the ________ chromosomes, which code for gender.

homologous: sex Pairs of chromosomes called homologous chromosomes code for the same traits that are all not related to gender while the sex chromosomes code for gender.

Metaphase II is more similar to metaphase of mitosis than to metaphase I because

in metaphase II, dyads align separately at the spindle equator. The alignment of chromosomes at the metaphase plate in metaphase II has chromosomes aligned separately, with sister chromatids facing opposite spindle poles.

The figure below shows a cell in which stage of the cell cycle?

interphase During interphase, the eukaryotic cell duplicates the contents of the cytoplasm, and DNA replicates in the nucleus. The duplicated chromosomes are not yet visible. A pair of chromosomes is outside the nucleus, and the nuclear envelope has not broken down.

Klinefelter syndrome can result from nondisjunction during

meiosis I or II in either parent. Klinefelter syndrome may result from nondisjunction in either the male or female, since both parents possess at least one X chromosome.

An individual with the karyotype 48, XYYY would have how many Barr bodies?

0 Barr bodies are extra X chromosomes. Most mammalian cells only utilize one of their X chromosomes, and the other one is packed away as a Barr body. This does not happen to Y chromosomes.

During prophase II, a diploid organism contains how many copies of each gene?

2 After DNA duplication, each chromosome consists of two sister chromatids, each containing one copy of each gene. With two homologues of each chromosome in a diploid, there will be four copies of each gene at prophase I. After separation of homologues, there will be two copies present during prophase II.

During G1 stage of interphase, a diploid organism contains how many copies of each gene?

2 During G1 stage, chromosomes have not been duplicated, so each cell contains one copy of each gene on each homologue, or two copies of each gene.

If there are 20 centromeres in a cell, how many chromosomes are there?

20 There is one centromere for every replicated chromosome that holds two sister chromatids together. In other words, two sister chromatids are considered one replicated chromosome. Once sister chromatids separate, they are each considered to be a full-fledged chromosome, which is now unreplicated.

Goats have a diploid chromosome number of 60. At prophase I, each cell would have ________ tetrads present, for a total of ________ chromatids.

30; 120 Each tetrad contains 2 chromosomes, so 60 chromosomes means that there would be 30 tetrads. Since each tetrad contains 4 chromatids, there would be 120 total chromatids.

During prophase I, a diploid organism contains how many copies of each gene?

4 After DNA duplication, each chromosome consists of two sister chromatids, each containing one copy of each gene. With two homologues of each chromosome in a diploid, there will be four copies of each gene.

Turner syndrome is associated with which of the following karyotypes?

45, XO An individual with Turner syndrome possesses only a single X chromosome, does not have a Barr body, and is female.

Camels have a diploid chromosome number of 70. At prophase II, each cell would contain how many chromatids?

70 Each tetrad contains 2 chromosomes and 4 chromatids. Each dyad at prophase II would contain 2 chromatids that are still attached at the centromere.

If a cell has 46 chromosomes at the beginning of mitosis, then at the end of anaphase there would be a total of

92 chromosomes. During anaphase, the duplicated chromosome separates and its chromatids move toward opposite poles of the cell. At this point, each chromatid is now considered a chromosome, since it consists of a complete DNA molecule. If 46 duplicated chromosomes pulled apart in anaphase, there would now be 92 chromosomes present in the cell until telophase and cytokinesis completes the chromosome reduction

When during the cell cycle are chromosomes visible?

??? A.)only during the G1 phase B.)Chromosomes are always visible. C.)only when they are being copied D.)during mitosis When a eukaryotic cell is not undergoing cell division, the DNA and associated proteins have the appearance of thin threads called chromatin. During mitosis, the chromatin condenses multiple times into large loops that produce highly compacted chromosomes; this starts to occur during prophase.

Which of the following is not a characteristic of cancer cells?

??? A.)produced by a mutation of a proto-oncogene B.)exhibit contact inhibition C.)have abnormal chromosomes D.)travel through the bloodstream to other parts of the body Contact inhibition stops the cell cycle when cells are surrounded by other cells. Cancer cells lose contact inhibition and continue to divide, even when totally surrounded by normal cells. When a proto-oncogene mutates it can become a cancer-causing gene.

A mutation that causes an increase in function in a tumor suppressor gene would not likely cause cancer because a tumor suppressor protein

??? does not promote cell division.

The energy of the electrons passing along the electron transport chain is used to produce

ATP. As oxidation-reduction occurs down the electron transport chain, energy is released that will be used to make ATP.

Why is it necessary for ATP to be used in the energy-investment phase of glycolysis?

Adding the phosphate to the glucose molecule allows the later reactions that take place in the energy payoff phase to occur. When phosphate is added to molecules in glycolysis, it activates the molecule, allowing later reactions to occur.

Cells grown in a petri dish tend to divide until they form a thin layer covering the bottom of the dish. Which of the following statements explains why this occurs?

Cell division can be inhibited by the proximity of other cells of the same type, a process called contact inhibition. The cells continued to grow as long as there was empty space. When cells come into contact with other cells they would stop growing, or be turned off. Cell division can be inhibited by the proximity of other cells of the same type, a process called contact inhibition.

What will occur if oxygen is not available in great enough quantity during cellular respiration?

Cellular respiration will shift towards anaerobic respiration. Overall, the role of oxygen in cellular respiration is to act as the final acceptor of electrons in the electron transport chain. In the absence of oxygen the cell will shift towards anaerobic respiration.

Which of the following statements is true?

Chromosomes are classified into two categories: the sex chromosomes that determine gender and autosomes that determine non-gender related traits. While sex chromosomes both determine gender, they can code for different traits depending on if they are XX or XY. Autosomes code for the same traits whether the individual is male or female.

A cell is inhibited during the S phase of its cycle. It will not reproduce due to lack of

DNA synthesis. In the cell cycle, the S phase is characterized by DNA synthesis prior to the active stages of mitosis. Chromosomes must duplicate at this stage or there will be an absence of chromosome duplicates to separate into daughter cells during division.

Cancer will occur if one copy of a mutant tumor suppressor gene is inherited.

False Mutant tumor suppressor genes, such as mutant alleles of RB, are often considered recessive because they are loss of function mutations. The normal copy will often suffice, but the predisposition to develop cancer is increased because only one mutation is needed to eliminate the function of the one normal copy, whereas a normal individual must accumulate mutations in both copies for the risk of cancer to increase.

Proto-oncogenes function by preventing cells from dividing uncontrollably.

False Proto-oncogenes function by stimulating the cell cycle, but only when the appropriate signals and growth factors are present.

Which of the following organelles would be abundant and in close proximity to the cell plate in a plant cell undergoing cytokinesis?

Golgi apparatus Cytokinesis is the division of the cytoplasm following mitosis that produces two daughter cells. A cell plate is characteristic of plant cells in cytokinesis. The Golgi apparatus produces the substance that forms the cell plate.

Which of the following statements is correct regarding the events of the cell cycle?

Interphase consists of G1, S, and G2 The cell cycle consists of interphase, mitosis, and cytokinesis. Interphase consists of G1, S, and G2

Rebecca found out that she has a mass of dividing cells called a tumor in her ovaries. She has had tests and is returning to the doctor. Which of the following would be the best news that Rebecca could receive from her doctor?

It is a benign tumor. During metastasis, a malignant tumor invades neighboring tissues and spreads through the body, while a benign tumor does not invade neighboring tissue.

Your friend has been on a diet and loses 15 pounds of fat. After studying cellular respiration, how can you explain where the weight went (how it was lost)?

It was released as carbon dioxide and water. Fats are oxidized to release energy. Hydrogen atoms are removed from glucose and added to oxygen atoms. The by-products are carbon dioxide and water.

Glycolysis and the citric acid cycle are similar in that they both produce

NADH and ATP. NAD+ accepts hydrogen atoms and becomes NADH in both reactions. NADH will be used in the last step of cellular respiration, the electron transport chain. ATP is also produced in both reactions.

During hibernation the rate of cellular respiration in a mammal is typically less than half the rate measured when the mammal is not hibernating. This slowed cellular respiration is probably accompanied by which of the following?

Reduced pulse rate and reduced body temperature. The extra energy from cellular respiration is lost in the form of heat. The decrease in cellular respiration and energy use would result in a decrease in the animal's heart rate and lower body temperature.

Stem cells that contain telomerase can be found in adults.

True Adult stem cells persist through an individual's lifetime and are used to produce new blood cells, skin cells, and other cell types that must be frequently replaced.

Losing weight can reduce an obese person's risk for cancer by up to 40%.

True The risk of cancer is up to 40% higher for some forms of cancer among obese men and women compared with people of normal weight. Thus, weight loss in these groups can reduce cancer risk.

Translocations can lead to cancer if they disrupt the genes that regulate the cell cycle.

True When the chromosomes of cancer cells become unstable, portions of the DNA double helix may be lost, duplicated, or scrambled. For example, a portion of a chromosome may break off and reattach to another chromosome. These events, called translocations, may lead to cancer, especially if it disrupts genes that regulate the cell cycle.

Cells grown in a petri dish tend to divide until they form a thin layer covering the bottom of the dish. If cells are removed from the middle of the dish, the cells bordering the open space will begin dividing until they have filled the empty space. What does this experiment show?

When cells come into contact with other cells, they stop growing. The cells continued to grow as long as there was empty space. When cells come into contact with other cells they would stop growing, or be turned off.

A positive genetic test for telomerase indicates that

a cell is probably cancerous. Telomerase is active in embryonic cells and some stem cells, but not adult cells. Active telomerase in an adult cell may indicate that it has become cancerous.

Cytokinesis usually, but not always, follows mitosis. If a cell undergoes mitosis and not cytokinesis, this would result in

a cell with two or more nuclei. If a cell goes through mitosis but not cytokinesis, it will have two nuclei within one cell.

A woman inherits a mutant BRCA1 allele from her mother. She has an increased risk of developing breast cancer because

a mutation in her normal BRCA1 allele may lead to cancer, whereas a normal individual would have to acquire two mutations (one in each allele) to develop cancer. The woman with the mutant BRCA1 allele has already accumulated one harmful mutation; a second mutation in this woman that affects the other BRCA1 allele is more likely to occur than two mutations, one in each copy of the BRCA1 gene, in a normal individual.

The functioning of an electron transport chain is analogous to

a person descending a flight of stairs one step at a time. High-energy electrons enter the electron transport chain by way of NADH and FADH2. Energy is captured through a series of reactions that release a small amount of energy each time. During these oxidation-reduction reactions, each of the carriers become reduced and then oxidized as electrons move down the system. As the pair of electrons is passed from carrier to carrier, energy is released in small amounts and captured for ATP production.

What must pyruvate be converted into before it can enter the citric acid cycle?

acetyl-CoA Pyruvate is oxidized, and a CO2 is given off. A C2 acetyl group is attached to coenzyme A, forming acetyl-CoA.

The citric acid cycle starts with ________ and yields ________.

acetyl-CoA, NAD, FAD, and ADP; carbon dioxide, NADH, FADH2, and ATP The citric acid cycle starts with the products from the preparatory step that meet up with C4 molecules already present in the mitochondrial matrix. Two carbons are pulled off and released as carbon dioxide, leaving a C4 molecule, which allows the process to occur again. Both NAD+ and FAD accept hydrogen atoms, resulting in NADH and FADH2.

The product of the preparatory reaction is

acetyl-CoA. Pyruvate from glycolysis is oxidized to a 2-carbon molecule that is carried by coenzyme A (CoA) to the citric acid cycle.

The human life cycle consists of

adults who are diploid and produce haploid gametes; these gametes fuse to produce a diploid zygote which grows into an adult. The human life cycle describes the process of alternating meiosis to produce haploid gametes (sperm and egg) which then fuse and produce a diploid zygote.

Which process is used to make bread rise?

alcoholic fermentation Yeasts are good examples of microorganisms that generate ethyl alcohol and CO2 when they carry out fermentation. When yeast is used to leaven bread, the CO2 makes the bread rise.

An individual with Swyer syndrome (46, XY) differs from an individual with Klinefelter syndrome (47, XXY) because

an individual with Klinefelter syndrome has a functional SRY gene on his Y chromosome, whereas an individual with Swyer syndrome does not. Swyer syndrome, or an XY female, results from an individual with an XY karyotype who lacks a functional SRY gene on the Y chromosome. Since this gene is necessary for development of the male phenotype, the individual develops as a female.

Which of the following phases results in separation of sister chromatids into daughter chromosomes?

anaphase II and anaphase of mitosis Both anaphase II of meiosis and anaphase of mitosis involve the splitting of sister chromatids to form daughter chromosomes. Separation of sister chromatids does not occur during anaphase I of meiosis.

It would be possible for a male and a female to have exactly the same ________, but they would have to differ in ________.

autosomes; sex chromosomes Since autosomes code for traits that are not related to gender, both a male and a female could have ones that are identical, but they would have to differ in sex chromosomes since they are different genders.

Refer to the figure below. Differentiated cells, such as nerve cells, would be in which of the following stages of the cell cycle?

b Specialized or differentiated cells are in the G0 stage; they will not divide but remain in the G0 phase.

The cristae of a mitochondrion are critical

both as a site for the electron transport chain and creating a space for concentration of H+. The cristae of mitochondria contain an ATP synthase complex that allows H+ to return to the matrix. The flow of H+ through the ATP synthase complex brings about a conformational change, which causes the enzyme ATP synthase to synthesize ATP from ADP+ P. ATP leaves the matrix by way of a channel protein.

By-products of cellular respiration include

carbon dioxide and water. (Carbon dioxide and water are both released as glucose is broken down. ATP is the desired product.)

Which of the following is not a function of meiosis?

cause an organism to grow Meiosis produces gametes and creates genetic variability, but it is not used to increase cell numbers of an organism.

Which of the following is not a characteristic of cancer cells?

cells that spend 90% of their lifetime in interphase Cancer is a disease of the cell cycle. When cells have abnormal nuclei, lose contact inhibition, lack differentiation, and have uncontrolled growth, these are all signs of cancerous cells.

What cellular process uses oxygen to break food down, producing ATP?

cellular respiration Cellular respiration is aptly named because just as we take in oxygen and give off carbon dioxide during breathing, so do the mitochondria in your cells. Cellular respiration occurs in every one of a human's cells and it is the reason we need to breathe. Glucose from our food and the oxygen we breathe are requirements for cellular respiration, a process that is completed within the mitochondria. This process occurs in all aerobic eukaryotes.

What is the structure that holds together the two sister chromatids that form a chromosome?

centromere A duplicated chromosome is composed of two identical halves, called sister chromatids, held together at a constricted region called a centromere.

The energy released from glucose by the process of cellular respiration is in the form of

chemical and heat energy. A yield of 36-38 ATP represents about 40% of the available energy in a glucose molecule. The rest of the energy is lost in the form of heat.

When glucose is broken down to CO2 and H2O, ________ energy is released and converted into ________.

chemical potential; ATP The energy stored in chemical bonds is known as chemical potential energy. When the bonds are broken, that energy is released. In cellular respiration, the energy stored in the bonds of glucose are broken, and the energy is harnessed to make ATP.

What structure is formed by two sister chromatids being held together by a centromere?

chromosome A duplicated chromosome is composed of two identical halves, called sister chromatids, held together at a constricted region called a centromere.

During meiosis II,

chromosomes line up separately, with sister chromatids facing opposite spindle poles. In meiosis II, the arrangement of chromosomes during metaphase resembles that of mitosis, with chromosomes aligned separately at the metaphase plate, and each sister chromatid facing the opposite spindle pole.

The looping of DNA around histone proteins

condenses a large amount of DNA so that it can fit into the cell. As DNA loops around histones, it coils the DNA into a bead-like structure called a nucleosome and allows the DNA to fit into a smaller space. In this way the approximately six linear feet of DNA can fit into the nucleus of a cell.

One major difference between meiosis I and meiosis II is that

crossing-over occurs in prophase of meiosis I but not in prophase of meiosis II. During meiosis I, homologous chromosomes pair up allowing synapsis and crossing-over to occur; next homologues are separated resulting in two haploid cells. In meiosis II the chromosomes align and sister chromatids are separated resulting in four haploid cells.

Which of the diagrams best illustrates the appearance of a chromosome or chromosome pair at the end of prophase I?

diagram 2 The chromosomes have been duplicated prior to meiosis. During prophase I, homologous chromosomes undergo synapsis, and crossing-over occurs. Thus, diagram 2 is the most accurate representation of the chromosome pair at the conclusion of prophase I.

Which of the diagrams represent a chromosome or chromosome pair in a cell at the end of prophase II?

diagram 4 Homologues separate during meiosis I. Thus, at prophase II, only one member of each homologous pair of chromosomes is present, with sister chromatids still attached at this point.

All but which one of the following results from nondisjunction?

diploidy Nondisjunction leads to either additional chromosomes (trisomy), additional pairs of chromosomes (polyploidy), or missing chromosomes (monosomy).

Which of the following lists is in the correct order, from the least inclusive to the most inclusive?

gene - allele - chromosome Alleles are alternative versions of genes. Chromosomes contain hundreds or thousands of genes, so the choice gene - allele - chromosome would be in the correct order, from least inclusive to most inclusive.

During crossing-over,

genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. Crossing-over occurs between nonsister chromatids of a tetrad, and results in new combinations of alleles. Crossing-over of sister chromatids would not result in new allele combinations.

During which stage of meiosis will the pairs of homologous chromosomes line up?

metaphase I During metaphase I, the tetrads attach to the spindle and align at the spindle equator, with each homologue facing opposite spindle poles. It does not matter which homologous chromosome faces which pole; therefore, all possible combinations of chromosomes will occur in the gametes.

For the figure shown here, indicate the correct stage of meiosis and diploid chromosome number.

metaphase I, 2n=4 Homologous chromosomes are aligned together at the metaphase plate, so this represents metaphase I. There are 2 homolgous pairs, so 2n=4. Thus, metaphase I, 2n=4, is the correct answer.

If tumor cells have a faulty, nonfunctional proteinase, they will be unable to undergo which of the following processes?

metastasis An additional mutation in a tumor cell that allows it to express proteinase can cause metastasis because it allows the cell to break down the underlying tissue and spread to other areas.

What organelle is used during the process of cellular respiration?

mitochondria Mitochondria break down food to release the chemical energy in the food molecules. Oxygen is consumed while carbon dioxide and water are released as by-products through this process called cellular respiration.

Some multicellular organisms, like the hydra, use asexual reproduction to produce a bud that leads to a new organism. This means that they are using

mitotic division to create new cells that become a new organism. Asexual reproduction gives rise to a new organism that is genetically identical to the parent organism. Multicellular organisms like plants and hydra can use this to produce offspring.

Swyer syndrome (46, XY, female appearance), would most likely result from

normal disjunction during meiosis, but deletion of a portion of the Y chromosome in the male parent. An individual with Swyer syndrome has a normal chromosome number, but lacks the SRY gene on the Y chromosome.

Which of the following processes and products are paired correctly?

oogenesis - 1n gamete Both spermatogenesis and oogenesis result in haploid (1n) gametes.

The final acceptor for hydrogen ions in aerobic cellular respiration is

oxygen. Oxygen attracts electrons to a greater degree than the carriers of the chain. Once oxygen accepts electrons, it combines with H+ to form a water molecule, which is one of the end products of cellular respiration.

Which of the following does not occur twice during meiosis?

pairing of homologous chromosomes Pairing of homologous chromosomes, or synapsis, only occurs during prophase I.

Cellular respiration is the opposite of what other cellular process?

photosynthesis During cellular respiration, carbohydrates are oxidized forming carbon dioxide. In photosynthesis, that carbon dioxide is reduced producing carbohydrates (glucose). Thus, these processes are opposites.

Susan was examining a cell under the microscope and noticed the formation of a cell plate in the midline of the cell and the formation of nuclei at opposite poles of the cell. The cell under examination was most likely a(n)

plant cell undergoing cytokinesis. Cytokinesis is the division of the cytoplasm following mitosis that produces two daughter cells. A cell plate is characteristic of a plant cell in cytokinesis.

The enzyme that converts pyruvic acid into acetyl-CoA requires vitamin B1, also called thiamine. Vitamin B1 has to be taken in through the diet of an individual. At what phase would cellular respiration come to a halt without B1?

preparatory reaction To enter the citric acid cycle, pyruvate must be converted into acetyl-CoA.

When you exhale, what two stages of cellular respiration produce the carbon dioxide you are breathing out?

preparatory reaction and citric acid cycle Carbons are pulled off of the carbon skeleton and released out of our bodies as carbon dioxide. The carbons are oxidized in the preparatory reaction step and in the citric acid cycle.

Some of the drugs used in chemotherapy work by

preventing spindle formation. Spindles are used by the cell to pull chromosomes to opposite sides of the cell during the cell cycle. If the function of the spindle has been compromised, the cells will not be able to divide.

Unicellular organisms undergo mitotic division to

produce new organisms. Mitotic cell division creates a new daughter cell that is identical to the parent cell and, in the case of unicellular organisms, this gives rise to a genetically identical new organism.

The figure below shows a cell in the mitotic stage of: (early mitotic spindle, centrosome, centromere, chromosome consisting of two sister chromatids)

prophase The chromatin is coiling together to form chromosomes, which is evident by the thick rods within the nucleus. The nuclear membrane is breaking apart as evident by the irregular shape of the nucleus. These both show that the cell is in prophase.

For the figure shown here, indicate the correct stage of meiosis and the diploid number of the cell.

prophase II, 2n=4 The cell is in prophase, as the chromosomes are not yet attached to the spindle apparatus. Prophase II with a chromosome number of 2n=4 would be correct for this diagram.

Which of the following represents the phases of mitosis in their proper sequence?

prophase, metaphase, anaphase, telophase Mitosis is the division of the nucleus; the stages are prophase, metaphase, anaphase, and telophase.

A product of glycolysis is

pyruvate. During glycolysis, a six-carbon glucose molecule is broken down into two three-carbon molecules of pyruvate.

What is oxidation?

removal of H+ ions to form new molecules Oxidation is the removal of hydrogen ions from a molecule. During cellular respiration they are removed from glucose and transferred to oxygen atoms forming water.

The energy source that drives the production of ATP in oxidative phosphorylation is the

removal of electrons and hydrogen from glucose. Electrons and hydrogen that are removed from glucose are donated to the electron transport chain and used to set up a hydrogen ion gradient. The diffusing of hydrogen down its electrochemical gradient drives the production.

The spindle serves two roles in mitotic cell division. These are to separate the

sister chromatids and to elongate the cell. Some of the microtubules that make up the spindle attach to the duplicated chromosomes and pull apart the sister chromatids while others overlap in the middle of the cell and slide past one another to push the centrosomes apart elongating the cell.

Crossing-over between sister chromatids does not result in recombination of genetic material, while crossing-over between nonsister chromatids does because

sister chromatids have the same alleles, while nonsister chromatids have different ones. In order for genetic material to be recombined, the exchange must occur between nonsister chromatids, since sister chromatids have identical information and nonsister chromatids have different alleles.

Cellular respiration can be described as the conversion of the energy

stored in food to energy stored in ATP. (Food contains energy trapped in bonds within molecules. Cellular respiration releases that energy and captures it again storing it within ATP molecules. ATP are energy-rich molecules that run cellular activities.)

If cancer is discovered at an early stage, which treatment method is most often used?

surgery Cancer treatments either remove the tumor or interfere with the cancer cells' ability to reproduce. For many solid tumors, removal by surgery is often the first line of treatment. When the cancer is detected at an early stage, surgery may be sufficient to cure the patient by removing all cancerous cells.

Ben was looking at onion root tip cells under the microscope in biology class. He saw one cell that had two nuclei within it. What stage of the cell cycle was this cell in?

telophase/cytokinesis Each new cell has its own nucleus. The cytoplasm is splitting, creating two separate cells. These activities are indicative of telophase with cytokinesis.

It is essential that germ cells undergo meiosis so that

the number of chromosomes is cut in half in gametes. Gametes have half the genetic material so that when sperm and egg fuse during fertilization, the resulting zygote has a full complement of DNA but does not have more than that.

Cancer occurs when

the regulation of the cell cycle is lost and uncontrolled cell division occurs. Cancer is a disease of the cell cycle. The regulation of the cell cycle is lost and uncontrolled cell division occurs.

When a portion of a chromosome breaks off and attaches to a different chromosome, this is called a

translocation. When the chromosomes of cancer cells become unstable, portions of the DNA double helix may be lost, duplicated, or scrambled. For example, a portion of a chromosome may break off and reattach to another chromosome. These events, called translocations, may lead to cancer, especially if it disrupts genes that regulate the cell cycle.

A protein that promotes apoptosis would be considered a(n)

tumor suppressor. Tumor suppressor proteins are generally defined as those that inhibit the cell cycle and/or promote apoptosis. Mutation of these proteins can lead to cancer because cells that are stimulated to undergo apoptosis will not respond to the signals and keep dividing.

A tetrad is composed of

two chromosomes with two sister chromatids each. A tetrad consists of two homologous chromosomes that consist of two sister chromatids each, for a total of four chromatids per tetrad.