Chapter 8 Mastering Biology
During anaphase II, _____.
sister chromatids separate and migrate toward opposite poles
The kinetochores are _____.
sites at which microtubules attach to chromosomes
An example of a cell that is 2n is a __________.
somatic cell
Cytokinesis often, but not always, accompanies _____.
telophase
Looking through a light microscope at a dividing cell, you see two separate groups of chromosomes on opposite ends of the cell. New nuclear envelopes are taking shape around each group. The chromosomes then begin to disappear as they unwind. You are witnessing _____.
telophase
At a critical point in meiosis, the chromosomes do not replicate. This occurs between _____.
telophase I and prophase II
The genetic material is duplicated
the S phase
DNA replication occurs in _____.
the S phase of interphase
What is different concerning the DNA in bacterial cells as opposed to eukaryotic cells?
the amount of DNA present, whether the DNA is housed in a nucleus or not, and whether the DNA is linear or circular
Crossing over is _____.
the exchange of homologous portions of nonsister chromatids
During _____ both the contents of the nucleus and the cytoplasm are divided.
the mitotic phase
Imagine I've taken a snapshot of the chromosomes in a hypothetical cell. Two chromosomes lined up. You and your twin and your friends and her twin. Part of that snapshot looks like this (duplicated chromosomes lined up by homologous pair). What stage of the lifecycle must that cell be in?
the start of meiosis I
During mitosis, the chromosomes move because _____.
they attach to a dynamic, precisely regulated mitotic spindle
Individual chromosomes are usually observed with a light microscope during mitosis, even though cells spend more time in interphase. This is because _____.
they have uncoiled to form long, thin strands
Meiosis is typically accomplished in _____.
three steps. All of the chromosomes are duplicated in a diploid cell, and then there are two cell divisions to produce a total of four haploid gametes.
In sexually reproducing multicellular organisms, the main functions of mitosis are _____.
tissue repair/replacement of damaged cells and growth and development
In a cell with eight chromosomes, one chiasma develops during meiosis I in only one particular pair of homologs. How many recombinant chromosomes will there be at the completion of meiosis II?
two
During prophase a homologous pair of chromosomes consists of _____.
two chromosomes and four chromatids
Mitosis and cytokinesis result in the formation of _____; meiosis and cytokinesis result in the formation of _____.
two diploid cells ... four haploid cells
At the end of telophase I of meiosis, as cytokinesis occurs, there are _____.
two haploid cells
What is this?
zygote (2n)
A human bone marrow cell in the prophase stage of mitosis contains 46 chromosomes. Therefore, there are a total of __________ sister chromatids in this cell.
92
Which of the following checkpoints does not occur late in G1? A check that chromosome replication has been successfully completed A check that the cell is large enough for division A check that nutrients are sufficient A check that growth factors are present
A check that chromosome replication has been successfully completed
What occurs during this stage of mitosis?
At metaphase, the mitotic spindle is fully formed and chromosomes are lined up in the center of the cell.
Which of these gametes contains one or more recombinant chromosomes?
B and C
A technique called flow cytometry is used by scientists and researchers to count or sort cells based on specific properties. By labeling cellular DNA with a fluorescent dye, flow cytometry can sort cells based on the amount of DNA present, thereby making it possible to distinguish between cells that are in different stages of the cell cycle. Flow cytometry is especially useful to the medical community because it can help with the diagnosis of certain types of cancers. Below is a typical set of data that you might obtain when running a flow cytometry experiment using a sample of healthy skin cells. Use this figure to help you answer the following question. Which peak represents cells that contain the most DNA?
C
Which of these cells is (are) haploid? Parent cell- A DNA replicates- B 2 daughter cells- C 4 daughter cells- D
C and D
In the laboratory, cancer cells fail to show density-dependent inhibition of growth in cell culture. What is one explanation that could account for this?
Cancer cells continuously secrete growth factors into the cell culture medium.
Which events occur during prophase? Chromosomes are replicated. Chromosomes condense and are attached to spindle fibers. The nuclear envelope breaks down. The sister chromatids break apart and begin to separate.
Chromosomes condense and are attached to spindle fibers and the nuclear envelope breaks down
Scientists commonly choose white blood cells that are going through mitosis to prepare karyotypes. Why?
During mitosis, chromosomes are more condensed than during interphase.
Which of these phases encompasses all of the stages of mitosis?
E
Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?
Extra copies of the other somatic chromosomes are probably fatal.
True or false. Mitosis takes place during M phase of the cell cycle, which is longer than interphase.
False
A skin cell of a red fox has 34 chromosomes. You look at the cell under a microscope and see that it has 34 chromosomes and one nucleus. Several hours later, you look at the same cell again and see that it has double the amount of DNA and one nucleus. A little while later, you see that it has 68 chromosomes and two nuclei. What stage of the cell cycle was this cell in when you viewed it at each time point?
First view: G1; second view: G2; third view: telophase
Consider the cell cycle shown below. Cells will usually divide if they receive the proper signal at a checkpoint in the _____ phase of the cell cycle.
G1
When examining cells in the laboratory, you notice that a particular cell has half as much DNA as the surrounding cells. It appears that this cell's cell cycle halted at checkpoint _____.
G1
Immune system cells enter a resting phase after undergoing mitosis. When activated - for example, by an infection - they can reenter the sequence of events in the cell cycle that leads to cell division. What would be the correct sequence of events?
G1, S, G2, M
Which of the following statements regarding genetic diversity is false? Genetic diversity is enhanced by independent orientation of chromosomes at metaphase I. Genetic diversity is enhanced by random fertilization. Genetic diversity is enhanced by crossing over during meiosis. Genetic diversity is enhanced by mitosis.
Genetic diversity is enhanced by mitosis.
Below are three statements. Classify them as examples of independent orientation, crossing over, or random fertilization. I: The formation of a zygote from an egg and a sperm is an unpredictable event. II: Random combinations of paternal and maternal chromosomes end up in gametes. III: An allele on the paternal chromosome 18 ends up on the maternal chromosome 18.
I: random fertilization; II: independent orientation; III: crossing over
What occurs during this stage of mitosis?
In anaphase, sister chromatids separate and become full-fledged chromosomes that move to opposite poles.
What occurs during this stage after mitosis?
In cytokinesis, the cytoplasm divides
What occurs during this stage of mitosis?
In prophase, microtubules form the mitotic spindle, and the nuclear envelope breaks up.
What occurs during this stage of mitosis?
In telophase, chromosomes become less condensed and new nuclear envelopes form.
What are the stages of meiosis?
Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis, Meiosis II
What are the stages of mitosis?
Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
What are the cell cycle stages?
Interphase- G1 phase, S phase, G2 phase Mitotic (M) phase- Mitosis, Cytokinesis
During binary fission, one copy of the duplicating chromosome moves to the opposite end of the cell. What does this achieve?
It ensures that each daughter cell receives one copy of the chromosome.
During binary fission, the replicated bacterial chromosome attaches to the plasma membrane by specialized anchor proteins. What is the purpose of this attachment between chromosome and membrane?
It ensures the separation of the replicated chromosomes as new membrane is made.
The chromosomes line up in the center of the cell during which phase of mitosis?
Metaphase
_________ is the spread of cancer cells from their site of origin to other sites in the body.
Metastasis
Which of the following statements regarding the function of mitosis is false? Mitosis allows organisms to grow. Mitosis allows organisms to reproduce asexually. Mitosis allows organisms to generate genetic diversity. Mitosis allows organisms to repair tissues.
Mitosis allows organisms to generate genetic diversity.
What occurs during this stage?
Most of the cell's lift is spent in interphase, when growth occurs. Cells that are about to divide replicate their DNA.
Trisomy for most autosomes is fatal, yet trisomy or even tetrasomy (four copies) of the X chromosome is not. What is the explanation for this difference?
Only one copy of the X chromosome is active, regardless of the total number of X chromosomes.
Inbreeding has a number of interesting effects. For one, highly in-bred strains (varieties) may carry identical forms of every gene. Mice have 40 chromosomes in their diploid (2n) set. How many genetically distinct kinds of gametes (gametes with different genetic characteristics) could be produced through meiosis in an in-bred strain where there are identical forms of every gene?
1
Imagine you found a hypothetical organism. You examine one of its gametes and you see that it contains 5 chromosomes. How many chromosomes will one of its body cells contain just before mitosis begins?
10
A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA in one of the grasshopper daughter cells?
100 units
There are species of coffee plant with 22, 44, 66, and 88 chromosomes. All but one of these species is considered to be an example of polyploidy. Plant geneticists believe that the original haploid number of chromosomes in coffee was _____.
11
A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
16
Baker's yeast is an organism with 32 chromosomes that can perform asexual or sexual reproduction and exist as both a diploid and haploid cell. After meiosis, how many chromosomes will be present in each cell?
16
Asexual reproduction requires ________ individual(s), whereas sexual reproduction requires _______ individual(s).
1; 2
How many pairs of autosomes do humans have?
22
Normal human gametes carry _____ chromosomes.
23
A certain species of animal has six pairs of chromosomes. How many DNA molecules are present in the nuclei of these animals during G2 phase?
24
What occurs in meiosis II?
4 haploid cells are produced and sister chromatids sparate
A human somatic cell contains _____ chromosomes.
46
Each cell in an individual with Down syndrome contains _____ chromosomes.
47
If we assume that crossing over does not occur, how many different combinations of chromosomes are possible in a zygote derived from diploid parents who each have three pairs of chromosomes?
64
Which of the following must occur for a plant or animal to grow and develop normally? The organism must be able to control the timing and rate of cell division in different parts of its body. The organism must receive a supply of the appropriate hormones from its parents. Sufficient light must be available to stimulate cell division. Sufficient oxygen must be available to stimulate cell division. Submit
The organism must be able to control the timing and rate of cell division in different parts of its body.
The M phase of mitosis and M phase of meiosis both occur after interphase. However, the two processes differ in the arrangement and behavior of their chromosomes. How?
The pairing up of homologous chromosomes and crossing over only occur during meiosis.
Within one chromosome, what is the relationship between the sequence of bases in DNA of one sister chromatid compared to the other?
The sequences are identical.
Centromeres divide and sister chromatids become full-fledged chromosomes during _____.
anaphase
Single sister chromatids are found in cells at mitotic _____.
anaphase and telophase
The function of mitosis is to produce daughter cells that _____.
are genetically identical to the parent cell (assuming no mutation has occurred)
In many organisms, including humans, chromosomes are found in homologous pairs. Homologous chromosomes _____.
are identical in the arrangement of their genes, but some versions of the genes may differ between the chromosomes
Mature human nerve cells and muscle cells
are permanently in a state of nondivision.
What name is given to this process?
asexual reproduction
A cell replicates its entire chromosomal DNA only __________.
before it is about to divide
Here i am representing a duplicated chromosome. What structure is represented by my waist where I am joined to my twin?
centromere
In the picture below, the chromosomal region where the nonsister chromatids are crossing over is called a(n) _____.
chiasma
A cleavage furrow forms in an animal cell during _____.
cytokinesis
At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.
cytokinesis
A cell is treated with a drug that prevents the formation of intracellular (within the cell) vesicles. Which of the following processes would be blocked?
cytokinesis in a plant cell
Which of the following is a correct representation of an event that occurs in mitosis? a- anaphase - the nuclear envelope disappears. b- prometaphase - there is movement of the chromosomes to the poles. c- prophase - chromosomes uncoil. d- metaphase - chromosomes line up on the equatorial plane.
d- metaphase - chromosomes line up on the equatorial plane.
Which of the following shows mitosis in the correct chronological order? a- telophase, prophase, anaphase, prometaphase, metaphase b- anaphase, prometaphase, metaphase, prophase, telophase c- prometaphase, metaphase, prophase, telophase, anaphase d- prophase, prometaphase, metaphase, anaphase, telophase
d- prophase, prometaphase, metaphase, anaphase, telophase Submit
When animal cells are grown in a petri dish, they typically stop dividing once they have formed a single, unbroken layer on the bottom of the dish. This arrest of division is an example of
density-dependent inhibition.
Meiosis starts with _____ cells and produces _____ gametes.
diploid ... haploid
A diploid zygote develops into ______ by mitosis
diploid organisms
fertilization forms a
diploid zygote
Are haploids or diploids used during mitosis?
diploids
Are zygotes haploids or diploids?
diploids
In bacterial cells, binary fission involves _____.
distribution of a copy of the single parental chromosome to each daughter cell
When forming buds, hydras _____.
divide by mitosis
Cytokinesis refers to _____.
division of the cell outside the nuclear material
Observations of cancer cells in culture support the hypothesis that cancer cells _____.
do not exhibit density-dependent inhibition
Gametes go through ____ to become a zygote.
fertilization
Haploid gametes join in
fertilization
Cytokinesis _____.
finishes mitosis by dividing the cytoplasm and organelles of the original parent cell into two separate daughter cells
Cytochalasin B is a chemical that disrupts microfilament formation. This chemical would interfere with _____.
formation of a cleavage furrow
What is the typical result when a diploid cell undergoes meiosis?
four haploid cells
Meiosis starts with a single diploid cell and produces
four haploid cells.
What are these?
gametes (egg and sperm cells)
Independent assortment and crossing over results in
genetic variation
During asexual reproduction, yeast cells can produce _____.
genetically identical offspring
At the conclusion of meiosis I, the daughter cells are _____.
haploid and the sister chromatids are joined
Meiosis forms
haploid gametes
Are gametes haploids or diploids?
haploids
Are haploids or diploids used during meiosis?
haploids
The _____ separate in meiosis I; the _____ separate in meiosis II.
homologous chromosomes ... sister chromatids
During prophase I of meiosis,
homologous chromosomes stick together in pairs.
Diploid organisms have
homologous pairs of chromosomes
Chromatids are _____.
identical copies of each other if they are part of the same chromosome
What occurs during meiosis I?
independent assortment and crossing over
Which processes lead to most genetic variation in sexually reproducing organisms?
independent orientation of chromosomes in meiosis, crossing over, random fertilization
Both mitosis and meiosis are preceded by
interphase
During _____ the cell grows and replicates both its organelles and its chromosomes.
interphase
During _____, the cell carries out its normal functions and the chromosomes are thinly spread out throughout the nucleus.
interphase
Eukaryotic cells spend most of their cell cycle in which phase?
interphase
Nucleoli are present during _____.
interphase
A cell preparing to undergo meiosis duplicates its chromosomes during
interphase.
A fragment of chromosome 21 reattaches to chromosome 21, but in the reverse direction. What is the name given to this change?
inversion
In humans, the _____ determines the sex of the offspring because _____.
male ... the male can contribute either an X or a Y chromosome
A _________ is an abnormally growing mass of cells that is actively spreading through the body.
malignant tumor
Homologous pairs of chromosomes include
maternal chromosomes and paternal chromosomes
Gametes are produced by _____.
meiosis
Sexual life cycle of diploid organisms involves
meiosis
Variation occurs when chromosomes are shuffled in _____.
meiosis
Looking through a light microscope at a cell undergoing meiosis, you see that the chromosomes have joined into XX-shaped tetrads. These tetrads are lined up along a plane that runs through the center of the cell. This cell is in _____.
meiosis I
Meiosis includes
meiosis I and meiosis II
If you look through a microscope and see a cell with chromosomes lined up two by two, what stage of cellular reproduction must you be looking art?
meiosis I only
At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?
metaphase
During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur?
prophase I.
A technique called flow cytometry is used by scientists and researchers to count or sort cells based on specific properties. By labeling cellular DNA with a fluorescent dye, flow cytometry can sort cells based on the amount of DNA present, thereby making it possible to distinguish between cells that are in different stages of the cell cycle. Flow cytometry is especially useful to the medical community because it can help with the diagnosis of certain types of cancers. Below is a typical set of data that you might obtain when running a flow cytometry experiment using a sample of healthy skin cells. Use this figure to help you answer the following question. If you used flow cytometry to sort a sample of cancerous cells that have been treated with a drug to prevent them from replicating their DNA, what peaks would you expect to see on the resulting flow cytometry data set?
A only
The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
Anaphase
Which of the following statements correctly describes the timing of DNA synthesis? DNA is synthesized in the S phase of interphase. DNA is synthesized only during mitosis. DNA is synthesized continuously. DNA is synthesized in G2 of interphase immediately preceding mitosis.
DNA is synthesized in the S phase of interphase.
The first step of bacterial replication is _____.
DNA replication
Which of the following statements regarding prokaryotes is false? In prokaryotes, daughter chromosomes are separated by an active movement away from each other and the growth of a new plasma membrane between them. Most prokaryotes reproduce by binary fission. Prokaryotic cells are generally smaller and simpler than eukaryotic cells. Prokaryotic chromosomes are more complex than those of eukaryotes.
Prokaryotic chromosomes are more complex than those of eukaryotes.
What are the stages of meiosis I?
Propase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis
The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
Prophase
What are the stages of meiosis II?
Prophase II, Metaphase II, Anaphase II, Telophase II, Cytokinesis
Which event occurs only during prophase I of the first meiotic division?
Synapsis of homologous pairs occurs.
The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
Telophase
What event will immediately follow the event shown in this image?
The cell will divide into two plant cells.
What would be the immediate consequence of destroying a cell's centrosomes?
The mitotic spindle would not form.
You have two flasks (labeled A and B) that each contain an equal population of normal animal cells. You place flask A in a machine called a shaking incubator, which shakes the flask at 37°C and keeps the cells moving so as to not allow them to adhere to the bottom of the flask. Flask B is allowed to sit in an incubator (without shaking) at 37°C. If you let the cells in each flask grow for a week, which of the following results are you most likely to observe?
The cells in flask B will have grown significantly, but the cells in flask A will have not grown at all.
You and your lab partner are observing a cell under a microscope, but you do not know whether it is a eukaryote or a prokaryote. Which of the following observations regarding the chromosomes would you use to immediately conclude that the cell is a eukaryote? The chromosomes contain very few proteins. The chromosomes are very simple in structure. The chromosomes are housed in a membrane-enclosed nucleus. The chromosomes are circular in structure.
The chromosomes are housed in a membrane-enclosed nucleus.
What must happen before a cell can begin mitosis?
The chromosomes must be duplicated.
If the diploid number of chromosomes in a certain animal is 6 (2n = 6), there are three sets of two homologous chromosomes each, or three pairs. How do these three pairs align and separate in meiosis?
They align and assort independently to form any of eight different combinations.
During cell division, what role do centrosomes play?
They organize the microtubules.
Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?
Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.
Label the diagram. the objects- a the x and y- b the entire thing- c
a- autosomes b- sex chromosomes c- karyotype
Which of the following occurs during mitosis? Two genetically different daughter cells result. Chromosomes replicate. Organelles replicate. Two daughter nuclei, one at each pole of the cell, are generated.
Two daughter nuclei, one at each pole of the cell, are generated.
In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos?
Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.
Which of the following indicates Turner syndrome? XXX XO XYY XXY
XO
Which of the following is a normal human female? XXY XX X XXX
XX
Label the diagram. both objects- a middle- b each strand- c
a- Pair of homologous chromosomes b- centromere c- sister chromatids
A _________ is a lump of abnormal cells that, although growing out of control, remains at its original site.
benign tumor
Bacteria divide by:
binary fission
Asexual and sexual reproduction differ in that sexual reproduction _____.
can produce great variation among the offspring
An individual with a malignant tumor is said to have _________.
cancer
The most common type of cancer is a _________; this type always originates in tissues that line organs.
carcinoma
Which of the following occurs during interphase? separation of newly formed DNA to opposite ends of the cell cell growth and duplication of the chromosomes cytokinesis a reduction in the size of the nuclear membrane
cell growth and duplication of the chromosomes
A benign and a malignant tumor differ in that _____.
cells of a benign tumor remain within the tumor, whereas cells of a malignant tumor can spread to other body tissues
Consider the process by which bacterial populations grow. What process performs a similar function in humans?
mitosis
Of the two processes we learned about, which is going on in my hand right now?
mitosis
Zygotes divide by _____ to become an embryo.
mitosis
Down syndrome can be the result of _____.
nondisjunction of chromosome 21 during meiosis
Spindle fibers attach to kinetochores during _____.
prometaphase
Chromosomes become visible during _____.
prophase
The phase of mitosis during which the mitotic spindle begins to form is
prophase
Crossing over occurs during _____.
prophase I
Synapsis occurs during _____.
prophase I
The correct order of events during meiosis is
prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.
What occurs in each stage?
prophase- mitotic spindle forming metaphase- sister chromosomes separating telophase and cytokinesis- nuclear envelopes forming
The exchange of parts between nonhomologous chromosomes is called _____.
reciprocal translocation
Benign tumors differ from malignant tumors in that the cells of a benign tumor _____.
remain confined to their original site
The function(s) of meiosis is/are _____.
reproduction (production of gametes)
Independent orientation of chromosomes at metaphase I and random fertilization are most like
shuffling cards and dealing out hands of poker.
In meiosis II, _____.
sister chromatids are separated
