BIOL 1406 CH11 LEARNING CURVE

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.

Which of the answer choices is part of the process of binary fission in prokaryotes?

formation of a new cell wall

Polar bodies are:

haploid

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

The cells would be smaller than normal.

Why are the X and Y chromosomes not considered homologous?

They do not carry the same set of genes.

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

Construction of a karyotype from an image of stained chromosomes is a technique by which a researcher can see and count chromosomes.

true

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

Nondisjunction can occur in both mitosis and meiosis.

true

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

true

There are no discernible phenotypic effects for an individual with the genotype XYY.

true

Which of the answer choices could be a proto-oncogene?

a gene encoding a cell-surface receptor a gene encoding a protein kinase a gene encoding a growth factor a gene encoding a G-protein

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

actin

During what step in meiosis do homologous chromosomes separate?

anaphase I

At which checkpoint would a cell become arrested if a chromosome was not properly aligned in the spindle?

at a checkpoint early in the mitotic phase

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

binary fission.

Which cellular conditions promote progression of the cell cycle?

binding of cyclins to CDKs the expression and synthesis of cyclin proteins the activation of CDKs the accumulation of cyclins

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

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

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

cytokinesis.

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

false

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

false

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

mitosis.

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.

Genes that participate in cell growth and division, but do not cause cancer, are:

proto-oncogenes.

Reproduction by mitotic cell division:

results in two daughter cells that are genetically identical.

Mitotic cell division is considered asexual because:

the daughter cells receive DNA from one parent cell, and the daughter cells are genetically identical.

Which are the functions of cyclins?

Cyclins activate kinases that regulate passage of cell cycle checkpoints.

What is the role of the protein FtsZ in prokaryotes?

It forms a ring at the site of constriction.

A gene associated with promoting normal cell division is called:

a proto-oncogene.

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.

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.

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.

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

G0

Meiosis _____ is similar to mitosis in that _____ separate.

II; sister chromatids

Which of the answer choices is a characteristic of meiotic cell division?

Meiotic cell division results in halving the number of chromosomes.

It is estimated that a human cell in G1 phase of the cell cycle contains 6 picograms of DNA in its nucleus. If you measure the DNA content at various stages of mitosis and meiosis, what amounts of DNA can be expected in nuclei at the following stages?

12; 12; 6; 6; 3

At the start of mitosis, how many sister chromatids are present in a human 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.

Suppose you are observing some cells with a microscope, and you see a cell that appears to be dividing. You can see that as the cell starts to pinch in half, the DNA seems to be attached to the plasma membrane via a membrane protein. On further analysis, you find that this organism's DNA is circular - that is, it consists of a closed loop. What can you conclude about this organism and its mode of cell division?

It is a prokaryote that is dividing by binary fission.

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?

Klinefelter; male

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

M

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

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

Replication of DNA in a eukaryote occurs during which phase of the cell cycle?

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.

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.

The prokaryotic protein FtsZ is evolutionarily related to eukaryotic tubulin. What does this mean?

The amino acid sequence for FtsZ is similar to tubulin. The overall protein structure of FtsZ is similar to tubulin. The two proteins evolved from a common ancestral protein. The gene sequence for FtsZ is similar to tubulin.

There are laboratory techniques that allow researchers to determine the amount of DNA in cell nuclei. If you measure the amounts of DNA at the end of mitosis and at the end of meiosis, how do they compare to the starting cell (starting from prophase during mitosis and from prophase I during meiosis)?

The daughter cells at the end of mitosis have one-half the amount of DNA, and the daughter cells at the end of meiosis have one-fourth the amount of DNA.

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.

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.