AP Bio Midterm Study Guide

Beginning with the fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

32

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

20

Eukaryotic chromatin is composed of

DNA and proteins

What is produced if a cell completes mitosis but does not undergo cytokinesis?

One sell with two nuclei, each identical to the nucleus of the parent

Humans produce skin cells by mitosis and gametes by meiosis. The nuclei of skin cells produced by mitosis will have

Twice as much DNA as the nuclei of gametes produced by meiosis

Compared to most prokaryotic cells, eukaryotic cells typically have

More DNA molecules and larger genomes

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

Prophase

If there are 20 centromere's in a cell at Anaphase of mitosis, how many chromosomes are in each daughter cell of the following cytokinesis?

10

Where do the microtubules on the spindle fibers originate during mitosis in animal cells?

Centrosome

Taxol is an anti-cancer drug extracted from the Pacific yew tree and prevents their depolymerization. Actively dividing cell is treated with Taxol becomes blocked in which phase of mitosis?

Metaphase

Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?

Golgi-derived vesicles

Movement of the chromosomes during anaphase would be most affected by a drug that prevents

shortening of microtubules

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels range from 3 to 6 picograms per nucleus. In which stage of the cell cycle would the nucleus contains six picograms of DNA?

G2

A group of cells is assayed for DNA content immediately following mitosis and is found to have average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and at the end of G2?

16; 16

A group of cells is Assayed for DNA content immediately before beginning mitosis and is found to have an average of 16 picograms of DNA per nucleus. How many picograms would be in a cell nucleus following completion of mitosis and cytokinesis?

8

The beginning of anaphase is indicated by which of the following?

Enzymatic cleavage of cohesion

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

Anaphase

What is a cleavage furrow?

a groove in the plasma membrane between daughter nuclei

You have the technology necessary to measure each of the following in a sample of animal cells: chlorophylls, organelle density, picograms of DNA, cell wall components, and enzymatic activity.

organelle density and enzymatic activity

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

Chromosome condensation would occur, but the chromosomes would fail to align at the metaphase plate

Where are the motor proteins that move chromosomes toward the poles of the mitotic spindle?

On the kinetochores

When a cell is in late anaphase of mitosis, which of the following may be seen?

A clear area in the center of the dividing cell

Diatoms and some yeasts are unicellular eukaryotes that have mechanisms of nuclear division that may resemble intermediate steps in the evolution of mitosis. Which of the following is a characteristic feature of nuclear division in these organisms?

The nuclear envelope remains intact during cell division

Cells from advanced malignant tumors frequently have very abnormal chromosomes as well as an abnormal number of chromosomes. What might explain the association between malignant tumors and chromosomal abnormalities?

Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.

Which is the first checkpoint in the Cell Cycle where a cell will be caused to exit the cycle of this point is not passed?

G1

Which of the following is released by platelets in the vicinity of an injury?

PDGF

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

Cyclins

Density-dependent inhibition is explained by which of the following?

As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing

Which of the following is true concerning cancer cells?

They evade the normal controls that trigger programmed cell death

Besides the ability of some cancer cells to divide uncontrollably, what else could be a logical result of a tumor?

Lack of appropriate cell death

Why do neurons and some other specialized cells divide infrequently?

They have been shunted into G0

Most animal cells exhibit anchorage dependence, which means that in order to divide

Cells must be attached to a substrate or extracellular matrix of tissue

The protein complex that activates progress through the M phase checkpoint will allow which of the following to occur?

Cleavage of cohesin proteins by separase

Researchers began a study of a cultured cell line. Their preliminary observations showed them that the cell line did not exhibit either density-dependent inhibition or anchorage dependence. What could they conclude right away?

The cells show characteristics of tumors

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?

It targets only rapidly dividing cells

You have a series of cells, all of which were derived from tumors. How might you determine which ones are malignant?

Prepare karyotypes to identify the ones with aberrant chromosome number or structure

Which image displays the chromosomal composition of one daughter nucleus at telophase of mitosis?

E

What is the correct chromosomal condition for a nucleus at prophase of mitosis?

B

What is the correct chromosomal condition for a nucleus in G1 of the cell division cycle?

E

If the cells who's nuclear material is shown in Figure 9.2 continues toward completion of mitosis, which of the following would occur next?

Segregation of daughter chromosomes toward the poles

In Figure 9.3, mitosis is represented by which numbered parts in the cycle?

IV

In Figure 9.3, G1 is represented by which numbered parts of the cycle?

I or V

In Figure 9.3, DNA synthesis is represented by which of the numbered parts of the cycle?

II

In Figure 9.3, which of the following represents the point in the cell cycle during which the chromosomes are replicated?

II

In Figure 9.3, which of the following numbered regions would contain cells at metaphase?

III only

In Figure 9.3, G2 is represented by which of the following parts in the cycle?

III only

Which of the following is the most plausible explanation for the difference in time spent in S phase by beta and gamma?

Gamma contains more DNA than beta

The best conclusion concerning delta is that the cells

Are actually in the G0 phase

Several organisms, including a number of protists, have intermediate mitotic organization.Which of the following is the most probable hypothesis regarding these intermediate forms of cell division?

They show some but not all of the evolutionary steps toward complete mitosis

Nucleotides can be radio-labeled before they are incorporated into newly forming DNA and can therefore be assayed to track their incorporation. In a set of experiments, a student- faculty research team introduced labeled T nucleotides into the culture of dividing human cells at specific times. Which of the following questions might be answered by such a method?

What is the length of the S phase of the cell cycle?

The research team used the setup to study the incorporation of labeled nucleotides into a culture of lymphocytes and found that the lymphocytes incorporated the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. They concluded that

Infection causes lymphocytes to divide more rapidly

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely

A plant cell in the process of cytokinesis.

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in

Cells with more than one nucleus

Which of the following does not occur during mitosis?

Replication of DNA

A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in

G1

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most-disrupted by cytochalasin B?

Cleavage furrow formation and cytokinesis

If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants?

Clone the plant asexually to produce an identical one

Which of the following descriptions correctly defines a genome?

the complete set of an organism's genes

Which of the following is the smallest unit that would contain a complete copy of the entire human genome?

one human somatic cell

If an organism is diploid and a certain gene found in the organism has 18 known alleles (variants), then any given organism of that species can/must have which of the following?

at most, 2 alleles for that gene

Which of the following is a true statement about sexual versus asexual reproduction?

In sexual reproduction, individuals transmit 50% of their genes to each of their offspring

At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype?

metaphase

Which of the following is true of a species that has a chromosome number of 2n=16?

Each cell has eight homologous pairs

Eukaryotic sexual life cycles show tremendous variation. Which of the following elements do all sexual life cycles have in common?

II. meiosis, III. fertilization, and IV. gametes

Which of these statements is true?

In humans, the 23rd pair, the sex chromosomes, determines whether the person is female (XX) or male (XY)

Referring to a plant's sexual life cycle, which of the following processes leads directly to the formation of gametes?

gametophyte mitosis

Which of the following is an example of alternation of generations?

A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte)

The human X and Y chromosomes..

include genes that determine an individual's sex

Which of the following describes a karyotype?

organized images of a cell's chromosomes

Which of the following types of cells would be produced by meiosis?

a haploid animal cell

Which of these is a way that the sexual life cycle increases genetic variation in a species?

by allowing crossing over

A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following?

Its gametes must have 23 chromosomes

A triploid cell contains three sets of chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, the cell would be expected to have which of the following?

63 chromosomes in 21 sets of 3

Which of the following statements best describes a karyotype?

a display of all of the chromosomes of a single cell

Which of the following cell types or organisms can utilize both mitosis ad meiosis in the correct circumstances?

a unicellular alga

The somatic cell of a privet shrub each contain 46 chromosomes. TO be as different as they are from human cells which have the same number of chromosomes, which of the following must be true?

Genes of privet chromosomes are significantly different from those in humans

In human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

length, centromere position, staining patter, and traits coded for by their genes

The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division malfunctions, and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following?

either anaphase I or II

If a cell has completed the first meiotic division and is just beginning meiosis II, which of the following statements describes the contents of this cell?

it has half the amount of DNA of the cell that began meiosis

Which of the following events might result in a human zygote with 45 chromosomes?

an error in either egg or sperm meiotic anaphase

After telophase I of meiosis, the chromosomal makeup of each daughter cell is..

haploid, and the chromosomes are each composed of two chromatids

How do cells at the completion of meiosis compare with cells that have replicated their DNA and are just about to begin meiosis?

They have half the number of chromosomes and one-fourth the amount of DNA

When does the synaptonemal complex disappear?

late prophase of meiosis I

Which of the following happens during meiosis I?

Homologous chromosomes of a pair are separated from each other

Chromatids are separated from each other during which of the following processes?

during both mitosis and meiosis II

Which of the following events occurs in meiosis but not in mitosis?

synapsis of chromosomes

During mitosis or meiosis, sister chromatids are held together by proteins referred to as cohesions. Such molecules must have which of the following properties?

they must be removed before sister chromatids or homologous chromosomes can separate

Which of the following structures is found in a pair of homologous chromosomes?

four sister chromatids

When we see chiasmata under a microscope, that lets us know that which of the following processes has occurred?

prophase I

To visualize and identify meiotic cells at metaphase I with a microscope, what would you look for?

pairs of homologous chromosomes aligned at the cell's center

Homologous chromosomes are aligned at the equator of the spindle in what phase....

II. metaphase I

Synaptonemal complexes form or are still present in what phase?

I. only prophase I

Centromeres of sister chromatids disjoin and chromatids separate in what phase?

VII. anaphase II

What steps take place in both mitosis and meiosis?

separation of sister chromatids

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?

approximately 8.4 million

Independent assortment of chromosomes during meiosis is a result of..

the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

During which process does independent assortment of chromosomes occur?

during meiosis I only

Which of the following statements best describes how often crossing over occurs in humans?

at least 1-3 times per chromosome pair

When homologous chromosomes cross over, what is the result?

specific proteins break the two strands of nonsister chromatids and re-join them

Refer to the life cycles illustrated in Figure 10.1. Which of the life cycles if (are) typical for animals?

A) I only

B) II only

C) III only

D) I and II

A) I only