Biology Chapter 11

At which stage of the cell cycle could you see sister chromatids with a microscope?

M

Replication of DNA in a eukaryote occurs during which phase of the cell cycle? Please choose the correct answer from the following choices, and then select the submit answer button. G1 phase

S phase

A researcher is studying phases of the cell cycle in a population of cells during which there is an increase in the DNA content. This stage is most likely:

S phase.

Muscle cells in the mammalian heart are multinucleate, meaning that multiple nuclei are present in the cytoplasm of individual large cells. Predict what is different about the cell cycle in a muscle cell.

cytokinesis does not occur

In which phase of mitosis does the mitotic spindle form?

prophase

The second meiotic division resembles mitosis because:

- chromosomes decondense during telophase II. - sister chromatids are separated during anaphase II to become the chromosomes of the daughter cells. - microtubules attach from opposite directions to the centromere of each sister chromatid pair. - the daughter cells have the same number of chromosomes as the parent cells.

Cell division is regulated by:

- signals that indicate a sufficient size of the cell. - signals that indicate that DNA has been replicated. - signals about the nutritional status of the cell. - growth factor signals.

In what way is cytokinesis in plant cells similar to binary fission in a bacterium?

Cell wall material is deposited to separate the daughter cells.

If you analyze the sequences of the two copies of any of the chromosomes shown in the karyotype, there would be slight sequence differences. What could account for the small differences between a few of the homologous chromosomes? Click to view full size.

Each homologous chromosome in a pair is from a different parent.

How must spindle microtubules attach to chromosomes during prometaphase of meiosis I?

Spindle microtubules from one pole must attach to both kinetochores in a pair of sister chromatids.

All cancers are caused by viruses.

false

A human cell with a total of 23 chromosomes is:

haploid.

To visualize chromosomes, a picture of each can be arranged such that homologous chromosomes are aligned with each other and arranged as pairs in order of decreasing size. What is this called?

a karyotype

Tumor suppressors oppose oncogenes by:

all of the above

During what step in meiosis do homologous chromosomes separate?

anaphase I

Asexual reproduction occurs in:

animal cells plant cells bacterial cells unicellular Eukaryotas

During meiosis I:

- nonsister chromatids exchange maternal and paternal DNA. - chromosomes undergo reductional division. -sister chromatids are not separated. - bivalents are formed during prophase I and are taken apart during anaphase I.

Which of the processes is most important for passage through the G1 cell cycle checkpoint?

Expression of gene encoding cyclin dependent kinases and activation of it and activation of DNA polymerase

Nondisjunction can only occur in the sex chromosomes and not the autosomes.

False

A cell that is not actively dividing is in what phase of the cell cycle?

G0

It is estimated that there are a total of 245 cells (roughly 50 trillion) in the adult human body. Starting from a fertilized egg, how many cell divisions would be required to produce 245, assuming that every cell divides in every cycle?

All the choices are correct according to that study.

Which statement regarding cancer, according to Douglas Hanahan and Robert Weinberg, are true?

Cancer cells can sometimes metastasize and travel throughout the body. Mutations in growth factor receptors are sometimes required for cancer cell division. Cancer cells can resist cell-death signals. Cancer cells typically secrete factors that promote blood vessel formation.

How would the loss of p53 activity affect a cell?

DNA damage could accumulate. CDK activity would not be appropriately regulated. The G1 /S checkpoint would not be functional.

Which statement is true regarding binary fission?

DNA replication of the circular bacterial chromosome during binary fission is a bidirectional process, starting at one point but progressing in opposite directions.

Predict what would happen if crossing over between homologous chromosomes occurred as part of mitosis.

Daughter cells would not be genetically identical.

Which one of the statements regarding the S cyclin-CDK complex is true?

It ensures that DNA is not replicated multiple times

What is the role of the protein FtsZ in prokaryotes?

It forms a ring at the site of constriction.

Which statement regarding the cell cycle is true?

It is regulated by cyclins and CDKs. Different levels of cyclins are observed at different cell cycle stages. It can be "paused" by the action of p53. It has many major cell cycle checkpoints.

Why would a compound that interferes with bacterial cell wall synthesis be useful for treating a bacterial infection?

It would limit growth of the bacterial population through cell division.

A person has the genotype XXY. What syndrome does this person have and what sex is the person? Please choose the correct answer from the following choices, and then select the submit answer button.

Klinefelter; male

Would genetic recombination result if crossing over occurred between sister chromatids?

No, because sister chromatids are genetically identical or nearly identical.

The most common form of hemophilia is a defect in blood clotting factor VIII, which is caused by a mutant form of a gene on the X chromosome. Boys who inherit that mutation from their mother suffer from uncontrolled bleeding. Girls carrying one copy of this mutation have near normal blood clotting. Uncommonly, a girl is born with hemophilia even though both parents have normal phenotypes. Which of the statements might explain hemophilia in a girl born to parents with normal blood clotting phenotypes?

Non- Disjunction during sperm formation resulted in her receiving no sex chromosome from her father and an X chromosome from her mother

What would happen to the daughter cells if the G2 phase of the parent cell is shortened?

The cells would be smaller than normal

Which of the following are true regarding CDKs?

The levels of CDK change with the cell cycle.

What would happen if a pair of sister chromatids only connected to the mitotic spindle at one of their kinetochores?

The sister chromatids would not separate. The chromosome would not line up properly at metaphase. One of the daughter cells would have an extra copy of that chromosome.

Why are the X and Y chromosomes not considered homologous?

They do not carry the same set of genes.

An example of second-division nondisjunction is when sister chromatids fail to separate during anaphase of meiotic cell division.

True

Nondisjunction can occur in both mitosis and meiosis.

True

Phosphorylated p53 is a protein that accumulates in the nuclei of cells that have damaged DNA where it functions to block the cell cycle and activate DNA repair. The p53 gene that encodes this protein is an example of a(n):

Tumor supressor gene

Why don't plant cells use a contractile ring to divide their daughter cells?

a contractile ring can't pinch a cell wall

A gene associated with promoting normal cell division is called:

a proto-oncogene.

What type of protein is being activated by the G1 /S cyclin-CDK complex to promote the expression of histone genes?

a transcription factor

What protein forms the contractile ring during cytokinesis in animal cells?

actin

Proto-oncogenes:

are the normal forms of genes that can mutate to cause cell division to be hyperactive. can be mutated by cigarette smoke to become triggers for cancer. can encode growth factors, cell surface receptors, or members of a signal transduction pathway.

The process of cell division in a prokaryotic cell is called:

binary fission.

What cellular process(es) is/are responsible for the increase in protein content associated with the gap phases of the cell cycle?

both transcription and translation

In meiosis, recombination occurs:

during only prophase I and involves exchange between chromatids of homologous chromosomes.

Reproduction by mitotic cell division:

results in two daughter cells that are genetically identical.

What process can account for the phenomenon wherein a normal XY male produces a sperm carrying two Y chromosomes?

second-division nondisjunction

The centrosome is:

the microtubule organizing center for the mitotic spindle.

Synapsis is best described as:

the pairing of homologous chromosomes in prophase I.

What is the function of histone proteins?

to package DNA in eukaryotic chromosomes

Evidence exists (especially in dinoflagellates) that mitosis evolved from binary fission. For example, in certain eukaryotic cells during mitosis, DNA is attached to the membrane of the nucleus (much like a circular chromosome of a bacterium is attached to the plasma membrane).

true

A cell in prophase I of meiosis has _____ as many copies of chromosomes as each of the daughter cells following cytokinesis of meiosis II.

twice

How many chromosome pairs are there in a normal human genome?

23

In human cells, at the end of mitosis and after cytokinesis, how many chromatids have moved into each daughter cell?

46

A student was studying cell growth using cells grown in laboratory cultures. The cultures were synchronized so that all of the cells passed through the same stage of the cell cycle at the same time. The cells were examined during five different periods of time, intervals (A-E). The amount of DNA present per cell was determined for each interval. The graph shows the result of this study.

S phase.

A researcher is evaluating the expression of p53 in cells she is culturing in the laboratory. She notices that in a small group of cells, high levels of phosphorylated p53 occur in the nuclei. What can she deduce about these cells?

These cells likely contain damaged DNA.

The division of the cell's cytoplasm in a eukaryotic cell is known as:

cytokinesis.

In which phase of mitosis does the nuclear envelope reform?

telophase

A couple has a baby that only has one X chromosome and no Y chromosome. This could have occurred because:

there was nondisjunction of sister chromatids in meiosis II of the father. Meiosis in the mother was normal. there was nondisjunction of the paired X and Y chromosomes in meiosis I in the father. Meiosis in the mother was normal. there was nondisjunction of homologous chromosomes in meiosis I in the mother. Meiosis in the father was normal. there was nondisjunction of the sister chromatids in meiosis II in the mother. Meiosis in the father was normal.