mastering bio chp 8
Your uncle has prostate cancer. Which of the following indicates improvement in his condition?
A decreasing PSA.
The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
Telophase
What must happen before a cell can begin mitosis?
The chromosomes must be duplicated
Which of the following is true regarding prostate cancer cells?
They can activate and inactivate certain genes.
A cell preparing to undergo meiosis duplicates its chromosomes during
interphase
In meiosis II, _____.
sister chromatids are separated
In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing __________ different gametes.
2^23
You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?
In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.
Meiosis starts with a single diploid cell and produces
four haploid cells.
A human bone marrow cell in the prophase stage of mitosis contains 46 chromosomes. Therefore, there are a total of __________ sister chromatids in this cell.
92
The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
Anaphase
In the laboratory, cancer cells fail to show density-dependent inhibition of growth in cell culture. What is one explanation that could account for this?
Cancer cells continuously secrete growth factors into the cell culture medium.
The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
Prophase
At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.
cytokinesis
A cell is treated with a drug that prevents the formation of vesicles. Which of the following processes depends on the formation of vesicles and would therefore be blocked?
cytokinesis in a plant cell
During binary fission, each copy of the duplicating chromosome moves to opposite ends of the cell. What does this achieve?
It ensures that each daughter cell receives one copy of the chromosome.
Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?
Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.
In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos?
Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.
During prophase I of meiosis,
homologous chromosomes stick together in pairs.
Looking through a light microscope at a cell undergoing division, you see that the condensed chromosomes have lined up along the midline of the cell. The homologous pairs are NOT joined in tetrads. Each chromosome takes its own place in line, independentof its homolog. You are witnessing _____.
metaphase of mitosis
Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?
Extra copies of the other somatic chromosomes are probably fatal.
Immune system cells enter a resting phase after undergoing mitosis. When activated—for example, by an infection—they can reenter the sequence of events in the cell cycle that leads to cell division. What would be the correct cell cycle sequence of events for these reactivated cells?
G1, S, G2, M
The chromosomes line up in the center of the cell during which phase of mitosis?
Metaphase
What would be the immediate consequence of destroying a cell's centrosomes?
The mitotic spindle would not form.
You are an oncologist. A patient presents with advanced prostate cancer and you follow standard protocol. What do you do?
The patient is treated with chemical castration.
You are an endocrinologist studying new treatments for prostate cancer. You have a patient with an unusually large level of dihydrotestosterone. Which of the following is true?
Your patient's cancer has become resistant to the standard treatment.
Fertilization joins _____ to produce a _____.
haploid gametes ... diploid zygote
In some organisms such as certain fungi and algae, cells undergo mitosis repeatedly without subsequently undergoing cytokinesis. What would be the consequence of this?
large cells containing many nuclei
If it weren't for _____, chromosome number would double with every generation of sexual reproduction.
meiosis
Duplication of the chromosomes to produce sister chromatids _____.
occurs in both mitosis and meiosis
In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.
prophase
The correct order of events during meiosis is
prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.
During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur?
prophase I.
Mitosis occurs in _____; meiosis occurs in _____.
somatic or body cells ... germ cells in the testes or ovaries
