Chapter 11

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

46

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

A contractile ring can't "pinch" a cell wall.

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.

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

Daughter cells would not be genetically identical.

Which statement regarding tumor suppressors are true?

Mutations affecting tumor suppressors can contribute to the development of cancers.

Suppose you analyze a time-lapse video of a cell under a microscope, and you observe what appears to be four chromatids tightly aligned along their lengths. Which of the answer choices is an interpretation of this observation?

The chromatids represent a bivalent and the cell is probably in Prophase I of meiosis.

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.

Why are the X and Y chromosomes not considered homologous?

They do not carry the same set of genes.

Which of the answer choices is true about gametes?

They fuse to form a new organism during fertilization.

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

a transcription factor

The development of cancer requires both the _____ of an oncogene and the _____ of a tumor suppressor.

activation; inhibition

When do sister chromatids separate in meiosis?

anaphase II

What characteristics do you expect to observe with a microscope if you investigate the division of mitochondria and chloroplasts in eukaryotic cells?

circular DNA attached to the plasma membrane and binary fission

Homologous chromosomes separate from each other in:

meiosis I.

The assembly of what cytoskeletal structures are initiated by the M cyclin-CDK complex?

microtubules

The division of genetic material in a eukaryotic cell is called:

mitosis

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

no, because sister chromatids are genetically identical or nearly identical

One of the important cell cycle checkpoints occurs during M phase. It inhibits progression to anaphase until all of the chromosome kinetochores are correctly attached to microtubules of the spindle apparatus. If anaphase of mitosis occurred when the kinetochore microtubule connected to only one of the two spindle poles but not the other, what could result?

nondisjunction

Genes that promote cancer are called:

oncogenes

Cell cycle checkpoints:

provide opportunities to check if the cell has carried out steps necessary for cell division. can be blocked by the protein p53. act as a brake on cell division if something is not right.

Synapsis is best described as:

the pairing of homologous chromosomes in prophase I

Meiosis _____ is similar to mitosis in that _____ separate.

II; sister chromatids

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.

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.

In a person with the genotype XXY, we can tell that nondisjunction must have taken place in the mother and not the father.

FALSE

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

G0

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.

A person has the genotype XXY. What syndrome does this person have and what sex is the person?

Klinefelter; male

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

M

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

The cells would be smaller than normal.

What important difference is there between meiosis in males and females? Refer to the figure shown.

The division of cytoplasm differs between males and females.

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.

all cancers are caused by virus

false

In mammals, females have two copies of the X chromosome, whereas males have only one copy. Dosage compensation (equalization of the numbers of each gene) is accomplished in mammals by:

females randomly inactivating one of the X chromosome in all cells.

If a human has the genotype XXXY, they would:

have 2 inactivated X chromosomes and be male.

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

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

What is the function of the centromere?

to attach the sister chromatids to each other

Some types of leukemia are the result of constitutively active (that is, "always on") growth factor receptors.

true

The alignment of chromosomes at metaphase of meiosis II is most similar to the alignment of chromosomes during metaphase of mitosis.

true

The occurrence of nondisjunction during mitosis can result in the development of certain cancers; however, nondisjunction is often thought of in relation to meiosis and the development of certain trisomies.

true

Proteins whose normal activities inhibit the cell cycle are:

tumor suppressors.