Exam 9: The Cell Cycle

-The unlettered circle at the top of the figure above 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-E show various combinations of these chromosomes.Which image displays the chromosomal composition of one daughter nucleus at telophase of mitosis?

During which phase of mitosis in animal cells do centrioles begin to move apart?

Which is the first checkpoint in the cell cycle that will cause a cell to exit the cycle if this point is not passed?

Which of the following does not occur during mitosis?

If there are 20 centromeres in a cell at anaphase of mitosis,how many chromosomes are there in each daughter cell following cytokinesis?

At which phase of mitosis do the sister chromatids become daughter chromosomes?

Which of the following characteristics is associated with cancer cells?

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 12 picograms of DNA per nucleus.How many picograms of DNA would be found in a nucleus at the end of G₁ and the end of G₂?

If cells are provided with nucleotides labeled with a radioactive isotope of hydrogen (³H),newly synthesized DNA will be radioactively labeled.In a set of experiments,a student-faculty research team introduced labeled T nucleotides into a culture of dividing human cells at specific times.Following a 30-minute incubation with the radiolabeled nucleotides,cells were lysed,and the DNA was isolated and tested for presence of radioactivity.Which of the following questions might be answered by such a method?

-In the figure above,which numbered segment(s)of the cycle would contain cells in G₂?

A cell in G2 of the cell division cycle contains 20 chromatids.How many centromeres are present in this cell?

Which of the following molecules is released by human platelets in the vicinity of a cut to stimulate proliferation of skin cells?

If cells are provided with nucleotides labeled with a radioactive isotope of hydrogen (³H),newly synthesized DNA will be radioactively labeled.In a set of experiments,a student-faculty research team introduced labeled T nucleotides into cultures of dividing human lymphocytes at specific times.A pathogen was introduced into one culture prior to the start of the experiment,and another culture was left untreated as a control.Following a 24-hour incubation with the radiolabeled nucleotides,cells were lysed,and the DNA was isolated and tested for presence of radioactivity.The research team found that lymphocytes exposed to a pathogen incorporated three times the amount of labeled nucleotide as the control.Which of the following hypotheses might explain these observations?

The data in the table above were obtained from a study of the length of time spent in each phase of the cell cycle by cells of three eukaryotic organisms designated beta,delta,and gamma.Which of the following is the most plausible explanation for the difference in time spent in S phase by beta and gamma?

A plant-derived protein known as colchicine can be used to poison cells by blocking the formation of the mitotic spindle.Which of the following would result if colchicine is added to a sample of cells in G₂?

The cell cycle is regulated at the molecular level by a set of proteins known as

The data in the table above were obtained from a study of the length of time spent in each phase of the cell cycle by cells of three eukaryotic organisms designated beta,delta,and gamma.The best conclusion concerning delta is that the cells