Biology Ch. 11

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

46

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.

Which of the answer choices is an accurate statement that accounts for why women with the genotype XXX are not phenotypically different from an XX female?

Only one X chromosome is active in each cell, regardless of how many X chromosomes there are in a cell.

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.

A protein that has regular up-and-down pattern of abundance during the cell cycle and that triggers progress of the cell cycle by activating kinases is called a:

cyclin

Meiosis _____ is sometimes called reductional division because _____.

I; the number of chromosomes is reduced by half

Meiosis _____ is similar to mitosis in that _____ separate.

II; sister chromatids

Proto-oncogenes:

can encode growth factors, cell surface receptors, or members of a signal transduction pathway. 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.

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

microtubules

What type of gene is c-src (cellular-src)?

proto-oncogene

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

proto-oncogenes.

Several years ago, a man noticed a small mole on his wrist. Years later, the mole grew in size and the man was diagnosed as having metastatic melanoma. This was likely the result of:

several mutations affecting proto-oncogenes and/or tumor suppressor genes.

Tumor suppressors oppose oncogenes by:

slowing cell division. repairing mutations. instructing defective cells to die. blocking the action of an oncogene. blocking the action of an oncogene.

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

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 the sister chromatids in meiosis II 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 homologous chromosomes in meiosis I in the mother. Meiosis in the father was normal.

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

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

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

true

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

true

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

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 two proteins evolved from a common ancestral protein. The gene sequence for FtsZ is similar to tubulin.

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

The cells would be smaller than normal.

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.

Suppose a research team does a detailed analysis of the DNA sequence of all three copies of chromosomes 21 from an individual with trisomy 21 (Down syndrome). They discover that each of the three chromosomes has a unique DNA sequence. Which of the answer choices is consistent with this observation?

The extra chromosome 21 resulted from first-division nondisjunction in one of the parents' gametes.

Suppose a research team does a detailed analysis of the DNA sequence of all three copies of chromosome 21 from an individual with trisomy 21 (Down syndrome). They discover that two of the three chromosomes are essentially identical in sequence, whereas the third chromosome has a significant number of sequence differences. Which of the answer choices is consistent with this observation?

The extra chromosome 21 resulted from second-division nondisjunction in one of the parents' gametes.

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

a transcription factor

A phragmoplast functions to:

form a new cell wall.

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

All of these choices are correct.

Recall the experiments of Peyton Rous and his colleagues. If he had found that filtered cancer cell extract could not cause cancer when injected into healthy animals, what could he have deduced?

An intact cancer cell is necessary to cause cancer. A large protein may cause cancer. Cancer may be caused by bacteria.

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.

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

M

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

Mitosis

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.

Suppose you analyze a time-lapse video of a cell under a microscope and you observe what appears to be crosslike structures within a bivalent. Which of the answer choices is an interpretation of this observation?

These structures represent crossing over between non-sister chromatids.

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

An early observation in the study of the development of sea urchin embryos was that there were several enzymes that became active and then inactive in synchrony with the pattern of rapidly repeating cell divisions. These enzymes had a common characteristic in that they phosphorylate (add phosphate groups to) other proteins. Furthermore, they are only active when bound to another protein—ones that vary in abundance at specific times during the cell cycle. These enzymes are:

cyclin dependent kinases.

An early observation in the study of the development of sea urchin embryos was that there were several proteins that appeared and then disappeared in synchrony with the pattern of rapidly repeating cell divisions. Because of this up-and-down pattern of abundance these proteins became known as:

cyclins.

Sexual reproduction results in an increase in genetic diversity because:

during metaphase I, the bivalents line up in a random orientation so that gametes inherit a random set of maternally and paternally derived chromosomes. during fertilization, the gametes that fuse are random so that a large number of chromosomal combinations are possible in the new organism. during prophase I, genes that are paternally and maternally derived recombine so that the gametes have chromosomes that are different from the parents' chromosomes.

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

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.