Bio exam 3
Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because
intracellular receptors are present only in target cells
The centromere is a region in which
chromatids remain attached to one another until anaphase
Movement of the chromosomes during anaphase would be most affected by a drug that prevents
prevents shortening of microtubules.
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
10
If there are 20 chromatids in a cell, how many centromeres are there?
10
A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2?
16; 16
Starting with a fertilized egg, a series of five cell divisions would produce an early embryo with how many cells?
32
When a cell is an anaphase of mitosis which of the following will he see?
A clear area in the center of the cell
Which of the following is an example of alteration of generations?
A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
In the human species, are somatic cells have 46 chromosomes. Which of the following can also be true?
A plant species has 46 chromosomes per cell
Which of the following can utilize both meiosis and mitosis in the correct circumstances?
A plantlike protist
Which of the following is required for motor proteins function in the movement of chromosomes toward the poles of the mitotic spindle?
ATP as an energy source
Centromere's of sister chromatids disjoint and chromatids separate
Anaphase II
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.
If an organism is deployed and a certain gene found in the organism has 18 known alleles, then any given organism of that species can have which of the following?
At most, two alleles for that Gene
Which of these statements is false?
At sexual maturity, ovaries and testes produce diploid gametes by meiosis.
For a newly evolving protest, what would be the advantage of using eukaryote like cell division rather than binary fission?
Cell division would allow for the orderly and efficient segregation of multiple linear chromosomes
Where do the microtubules of the spindle originate during meiosis in both plant and animal cells?
Centrosome
Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?
Chromosomally abnormal cells can still go through cell cycle checkpoints.
The drug cytochalasin B blocks the function of Acton. Which of the following aspects of the 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.
For anaphase to begin, which of the following must occur?
Cohesin must be cleaved enzymatically.
Once they had determine which cells were dividing, between wanted to use a non-radioactive method to track with various physiological factors affect the action of the pathogen. Which of the following would be effective, simple, and safe?
Counting the frequency of cells in mitosis
Which of the following is a protein synthesized at specific times during the cell cycle that forms a catalytically active complex?
Cyclin
To view and analyze human chromosomes in a dividing cell, which of the following is required?
DNA stain and a light microscope
Which of the following is true of a species that has a chromosome number of 2n= 16?
Each cell has eight homologous pairs.
A particular cell has half as much DNA as some cells in a mitotically active tissue. The cell in question is most likely in
G1
After which checkpoint is the cell first committed to continue the cell cycle through M?
G1
Measurement of the amount of DNA per nucleus were taken on a large number of cells from growing fungus. The measure do you know levels range from 3 to 6 pictograms per nucleus. In which state of the cell cycle to the nucleus contains six pictograms of DNA?
G2
The somatic cells 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 than those in humans
After Telophase 1 of meiosis, the chromosomal make up of each daughter cell is
Haploid, and the chromosomes Are each composed of two chromatids.
Which of the following happens at the conclusion of meiosis one?
Homologous chromosomes are separated
Which of the following is a true statement about sexual versus asexual production?
In sexual production, individuals transmit 50% of their genes to each of their offspring.
If a cell has completed the first meiotic division and is just beginning meiosis II, which of the following is an appropriate description of its contents?
It has half the amount of DNA as the cell that began meiosis.
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?
It interferes with rapidly dividing cells.
A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following?
Its gametes must have 23 chromosomes.
You have a series of cells, all of which were derived from tumors, and you first need to find out which ones are malignant. What could you do?
Karyotype samples to look for unusual size and number of chromosomes.
In a 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 and the pear have in common?
Length, centromere position, staining pattern, and traits coded for by their genes.
Why is apoptosis potentially threatening to the healthy neighbors of a dying cell?
Lysosomal enzymes exiting the dying cell would damage surrounding cells
Which of the following is a function of those spindle microtubules that do not attach to kinectochores?
Maintaining the region of overlap of microtubules in the cells center
Homologous chromosomes move to opposite poles of a dividing cell during
Meiosis I
Eukaryotic sexual lifecycles show tremendous variation. The following elements, which do all sexual lifecycles have in common?
Meiosis, fertilization, and gametes
Tetrads of chromosomes are lined at the equator of the spindle; alignment determines independent assortment.
Metaphase I
Synaptonemal complexes form or are still present.
Prophase I
When we see chiasmata under a microscope, that lets us know which of the following has occurred?
Prophase I
Which of The following does not occur during mitosis?
Replication of the DNA
At the M phase checkpoint, the complex allows for what to occur?
Separase enzyme cleaves cohesins and allows chromatids to separate.
Which of the following steps takes place in both mitosis and meiosis?
Separation of sister chromatids
To visualize and identify meiotic cells at metaphase with a telescope, what would you look for?
Tetrads all aligned at the cells center
A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation?
The cell would undergo normal mitosis, but fail to enter the next G1 phase.
A research team 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.
Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?
The chromosomes are "reeled in" by the contraction of spindle microtubules, and motor proteins of the kinetochores move the chromosomes along the spindle microtubules.
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?
The chromosomes would coil and shorten but have no spindle to which to attach.
The research team establish similar lymphocyte cultures from a number of human donors. They found that the increase in lymphocyte incorporation after pathogen introduction was slightly lower and some of the female teenagers and significantly lower in each of the elderly persons. They repeated the study with a larger number of samples we got the same results. What might be among the research teams conclusions?
The elderly persons samples demonstrated their lowered immune responses
A cell divides to produce two daughter cells that are genetically different.
The statement is true for meiosis I only.
Independent assortment of chromosomes occurs
The statement is true for meiosis I only.
Chromatids are separated from each other
The statement is true for mitosis and meiosis II.
All cell cycle checkpoints are similar in which way?
They activate or inactivate other proteins.
Why do neurons and some other specialized cells divide in frequently?
They have been shunted into G0.
How do you cells at the completion of my house is comparable sales that have replicated the DNA and are just about to begin meiosis?
They have half the number of chromosomes and 1/4 the amount of DNA.
Weather during mitosis or meiosis, sister chromatids are held together by proteins referred to as cohesions. Search molecules must have which of the following properties?
They must be removed before anaphase can occur
Several organisms, primarily protists, have what are called intermediate mitotic organization. These protists are intermediate in what sense?
They show some but not all of the evolutionary steps toward complete mitosis
When the cell has just completed Tele phase, which of the following does he see?
Two small cells with chromatin
Which of the following is true concerning cancer cells?
When they stop dividing, they do so at random points in the cell cycle; they are not subject to cell cycle controls; and they do not exhibit density-dependent inhibition when growing in culture.
What is a cleavage furrow?
a groove in the plasma membrane between daughter nuclei
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.
For a species with a haploid number 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?
about 8 million
Which of the following proteins are involved in binary fission as well as eukaryotic mitotic division?
actin and tubulin
Which of the following might result in a human zygote with 45 chromosomes?
an error in either egg or sperm meiotic anaphase
Which of the following best describes a frequency of crossing over in mammals?
at least 1-2 per chromosome pair
How does the sexual life cycle increase the genetic variation in a species?
by allowing crossing over
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
cells with more than one nucleus
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
centrosome
Experiments with cohesions have found that
cohesions are protected from cleavage at the centromere during meiosis I.
One Difference between cancer cells in normal cells is that cancer cells
continue to divide even when they are tightly packed together.
One difference between cancer cells in normal cells is that cancer cells
continue to divide even when they are tightly packed together.
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to
disruption of mitotic spindle formation.
The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division goes awry 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
The human genome is minimally contained in which of the following?
every human cell
Referring to a plant sexual life cycle, which of the following terms describes the process that leads directly to the formation of gametes?
gametophyte mitosis
After telophase I of meiosis, the chromosomal makeup of each daughter cell is
haploid, and the chromosomes are each composed of two chromatids
The human X and Y chromosomes
include genes that determine an individual's sex
Nucleotides can be radiolabeled 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 used labeled T nucleotides and introduced these into the culture of dividing human cells at specific times. 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
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
lack of appropriate cell death
When does the synaptonemal complex disappear?
late prophase of meiosis I
In a 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 pattern, and traits coded for by their genes
At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype?
metaphase
If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the spindle apparatus, at which stage will mitosis be arrested?
metaphase
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. Which would you expect to increase significantly from M to G1?
organelle density and enzymatic activity
At which phase are centrioles beginning to move apart in animal cells?
prophase
Which of the following does not occur during mitosis?
replication of DNA
Which of the following occurs in meiosis but not in mitosis?
synapsis of chromosomes
During which phase of mitosis do the chromatids become chromosomes?
telophase
Which of the following defines a genome?
the complete set of an organism's genes
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, Taxol must affect
the formation of the mitotic spindle
A karyotype results from which of the following?
the ordering of human chromosome images
Independent assortment of chromosomes 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.
Why do chromosomes coil during mitosis?
to allow the chromosomes to move without becoming entangled and breaking
Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic (animal) nucleus. It might consist of which of the following?
two long strands of DNA plus proteins
A tetrad includes which of the following sets of DNA strands?
two sets of sister chromatids that have synapsed