Gen Bio Test 3

_____ is a carcinogen that promotes colon cancer.

Fat. A diet high in fat increases the risk of both colon and breast cancer.

Did doctors ask Henrietta Lacks' permission to take her cells, and was she paid for them?

She was never told that her cells were being taken, and neither she nor her family has been compensated.

When cells were first taken from Henrietta Lacks, she was _____.

suffering from cervical cancer

How did doctors harvest and culture cells from Henrietta Lacks?

Cells were taken while she was being treated for cancer many years ago, and these cells have been cultured in the lab ever since.

Can you recognize the eight stages of meiosis based on the location and behavior of the chromosomes? Drag the diagrams of the stages of meiosis onto the targets so that the four stages of meiosis I and the four stages of meiosis II are in the proper sequence from left to right. (Note that only one of the two daughter cells is shown for meiosis II.) *See Picture in School Notes Folder on Desktop*

Hint- start with more and move to less. prophase- chromosomes in free space metaphase- chromosomes lined along middle anaphase- chromatids start splitting telekinesis- two separate cells begin to form (figure 8 shape)

Crossing over normally takes place during which of the following processes?

Meiosis I

What is a major difference between meiosis II and mitosis in a diploid animal?

Meiosis II takes place in a haploid cell, while mitosis takes place in diploid cells.

Can you recognize the eight stages of meiosis based on the location and behavior of the chromosomes?

Meiosis involves two sequential cellular divisions. In meiosis I, homologous chromosomes pair and then separate. Thus, although the parent cell is diploid (containing two chromosome sets, one maternal and one paternal), each of the two daughter cells is haploid (containing only a single chromosome set). In meiosis II, the sister chromatids separate. The four daughter cells that result are haploid.

Which of these is NOT a carcinogen? UV light Cigarette smoke Fat Testosterone

all of the above are carcinogens

The M-phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does not happen, cells would most likely be arrested in _____.

metaphase

Cells taken from Henrietta Lacks have been used for experiments leading to

new treatments for cancer,tests of the effects of atomic radiation on life, the development of a polio vaccine

The stages of mitosis were originally defined by cellular features observable through a light microscope. Name the oder in which they occur.

prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis.

Mitosis unfolds through a sequence of stages marked by specific events in the cell. The structural changes in the cell are brought about by a series of tightly coordinated underlying mechanisms. Sort each process into the appropriate bin to indicate the stage of mitosis in which it occurs. If a process occurs in more than one stage, sort it to the stage when it first occurs.

prophase: cohesions join sister chromatids of duplicated chromosomes, tubulins assemble into spindle microtubules prometaphase: microtubules attach to kinetochores metaphase: kinetochores are motionless in relation to poles of cell anaphase: cohesions break down, kinetochores move toward poles of cell telophase: spindle microtubules disassemble

Which of the following is a true statement about sexual vs. asexual reproduction? A) In asexual reproduction, offspring are produced by fertilization without meiosis. B) Asexual reproduction produces only haploid offspring. C) Asexual reproduction, but not sexual reproduction, is characteristic of plants and fungi. D) In sexual reproduction, individuals transmit 50% of their genes to each of their offspring. E) Sexual reproduction requires that parents be diploid.

D. In sexual reproduction, individuals transmit 50% of their genes to each of their offspring.

The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid. Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II. During anaphase of both meiosis I and meiosis II, the DNA content (number of copies of chromosomes) in a cell is halved. However, the ploidy level changes only when the number of unique chromosome sets in the cell changes. This occurs only in meiosis I (where separation of homologous chromosomes decreases the ploidy level from 2n to n and produces daughter cells with a single chromosome set).

The mitotic spindle consists of two types of microtubules: kinetochore microtubules and nonkinetochore microtubules. In animal cells, these two types of microtubules function differently in the stages of mitosis.

During prophase, the microtubules of the mitotic spindle lengthen. During anaphase, the nonkinetochore microtubules lengthen and move past each other, and the kinetochore microtubules shorten. During telophase, the nonkinetochore microtubules disassemble.

Which of the following is true of kinetochores?

They are sites at which microtubules attach to chromosomes. As the spindle depolymerizes, the kinetochores appear to move along the spindle fiber, dragging the attached chromosomes with them.

What property of Henrietta Lacks' cells was most unusual when they were grown in the laboratory?

They continue to divide and multiply after decades of culture.

Which of the following is true of benign tumors, but not malignant tumors?

They remain confined to their original site. Benign tumors can often be surgically removed because their boundaries are well defined, whereas some malignant tumors go on to metastasize.

Crossing over plays a critical role in increasing the genetic variation among offspring of sexual reproduction. It is important to understand how crossing over occurs and its consequences in meiosis. Look carefully at the diagrams depicting different stages in meiosis in a cell where 2n = 6. Assume that the red chromosomes are of maternal origin and the blue chromosomes are of paternal origin. Name where events or results of crossing over are possible.

anaphase II- yes metaphase II- no Prophase I-no metaphase I- yes Crossing over occurs during prophase I when homologous chromosomes loosely pair up along their lengths. Crossing over occurs only between nonsister chromatids within a homologous pair of chromosomes, not between the sister chromatids of a replicated chromosome. Only segments near the ends of the chromatids, not segments nearest the centromeres, can exchange DNA.

How are sister chromatids and homologous chromosomes different from each other? a) They are not different. Homologous chromosomes and sister chromatids are both identical copies of each other b) sister chromatids are only formed during mitosis. Homologous chromosomes are formed during meiosis c) homologous chromosomes are identical copies of each other. One sister chromatid comes from the father, and one comes from the mother d) Homologous chromosomes are closely associated with each other in both mitosis and meiosis. Sister chromatids are only associated with each other during mitosis. e) Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.

e) Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication. One homologous chromosome comes from the father, and the other comes from the mother. Sister chromatids are identical copies of each other.

Consider an animal cell in which motor proteins in the kinetochores normally pull the chromosomes along the kinetochore microtubules during mitosis. Suppose, however, that during metaphase, this cell was treated with an inhibitor that blocks the function of the motor proteins in the kinetochore, but allows the kinetochore to remain attached to the spindle. The inhibitor has no effect on any other mitotic process, including the function of the nonkinetochore microtubules. Consider three questions concerning the animal cell that has been treated with the inhibitor. Drag the labels to answer the questions. Labels may be used once, more than once, or not at all.*See picture in school file*

1. Will this cell elongate during mitosis? Yes 2. Will the sister chromatids separate from each other? Yes 3. Will the chromosomes move to the poles of the cell? No The inhibitor does not affect the cleavage of cohesins (the proteins that hold the sister chromatids together), the attachment of the chromosomes to the kinetochore microtubules, or the elongation of the cell due to the nonkinetochore microtubules. The inhibitor only affects the motor protein that pulls the chromosome along the kinetochore microtubule in anaphase. Thus, in the treated cell, the sister chromatids can still separate at the beginning of anaphase due to the fact that the cell is elongating (the centrosomes at the poles of the cell are moving farther apart) and the kinetochore microtubules still connect the chromosomes to the centrosomes. However, because the chromosomes cannot move along the kinetochore microtubules, they will never reach the poles of the cell.

The unlettered circle at the top of the figure shows a diploid nucleus with four chromosomes that have not yet replicated. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is black, and the other is gray. The circles labeled A to E show various combinations of these chromosomes. What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis? *See picture in school notes*

E