BIO 1012 Chapter 8
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
A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
16
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
In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing __________ different gametes.
2^23
Each somatic cell in an individual with Down syndrome contains _____ chromosomes.
47
In a cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.
5
Which of the following checkpoints does not occur late in G1?
A check that chromosome replication has been successfully completed
Polyploidy is involved in which of the following examples?
A normal watermelon has 22 chromosomes but seedless watermelons have 33 chromosomes.
asexual reproduction is when
A single individual is reproducing.
Which of the following statements regarding prokaryotes is false? A) Prokaryotic chromosomes are more complex than those of eukaryotes. B) Most prokaryotes reproduce by binary fission. C) Prokaryotic cells are generally smaller and simpler than eukaryotic cells. D) In prokaryotes, daughter chromosomes are separated by an active movement away from each other and the growth of a new plasma membrane between them.
A) Prokaryotic chromosomes are more complex than those of eukaryotes.
You are asked to culture an unidentified sample of animal tissue. You notice that the cells seem to fail to exhibit density-dependent inhibition. The source of this tissue sample is most likely A) a cancerous tumor. B) skin from a human. C) a liver from a cow. D) the sperm-producing tissue of the testis.
A) a cancerous tumor.
Which of the following is a feature of plant cell division that distinguishes it from animal cell division? A) formation of a cell plate B) formation of a cleavage furrow C) lack of cytokinesis D) production of four (rather than two) new cells per mitotic division
A) formation of a cell plate
Two chromosomes in a nucleus that carry genes controlling the same inherited characteristics are A) homologous chromosomes. B) heterologous chromosomes. C) complementary chromosomes. D) parallel chromosomes.
A) homologous chromosomes.
Eukaryotic cells spend most of their cell cycle in which phase? A) interphase B) prophase C) metaphase D) telophase
A) interphase
At the start of mitotic anaphase, A) the centromeres of each chromosome come apart. B) the chromatid DNA replicates. C) nuclear envelopes begin to form around the chromosomes. D) equivalent and complete collections of chromosomes have reached the two poles.
A) the centromeres of each chromosome come apart.
Looking into your microscope, you spot an unusual cell. Instead of the typical rounded cell shape, the cell has a very narrow middle separating two bulging ends. It sort of looks like the number 8! You realize that this cell is A) undergoing cytokinesis. B) in the S phase of interphase. C) in the G1 phase of interphase. D) about to undergo mitosis.
A) undergoing cytokinesis.
The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
Anaphase
Asexual reproduction requires ________ individual(s), whereas sexual reproduction requires _______ individual(s). A) 1; 1 B) 1; 2 C) 2; 1 D) 2; 2
B) 1; 2
Which of the following statements regarding the function of mitosis is false? A) Mitosis allows organisms to grow. B) Mitosis allows organisms to generate genetic diversity. C) Mitosis allows organisms to reproduce asexually. D) Mitosis allows organisms to repair tissues.
B) Mitosis allows organisms to generate genetic diversity.
Which of the following statements best represents the theory of pangenesis developed by Hippocrates? A) Pregnancy is a spontaneous event, and the characteristics of the offspring are determined by the gods. B) Particles called pangenes, which originate in each part of an organism's body, collect in the sperm or eggs and are passed on to the next generation. C) Offspring inherit the traits of either the mother or the father, but not both. D) Heritable traits are influenced by the environment and the behaviors of the parents.
B) Particles called pangenes, which originate in each part of an organism's body, collect in the sperm or eggs and are passed on to the next generation.
Which of the following must occur for a plant or animal to grow and develop normally? A) The organism must receive a supply of the appropriate hormones from its parents. B) The organism must be able to control the timing and rate of cell division in different parts of its body. C) Sufficient light must be available to stimulate cell division. D) Sufficient oxygen must be available to stimulate cell division.
B) The organism must be able to control the timing and rate of cell division in different parts of its body.
A pair of sex chromosomes found in a human male is most like A) a pair of blue jeans. B) a bride and groom. C) a knife, fork, and spoon. D) identical twins.
B) a bride and groom.
Which of the following shows the greatest promise as a cancer chemotherapy agent? A) a drug that interferes with cellular respiration B) a drug that prevents mitotic spindle from forming C) a drug that prevents crossing over D) a drug that prevents tetrad formation
B) a drug that prevents mitotic spindle from forming
The process by which the cytoplasm of a eukaryotic cell divides to produce two cells is called A) mitosis. B) cytokinesis. C) binary fission. D) telophase.
B) cytokinesis.
As a patch of scraped skin heals, the cells fill in the injured area but do not grow beyond that. This is an example of A) density-independent inhibition. B) density-dependent inhibition. C) anchorage independence. D) growth factor inhibition.
B) density-dependent inhibition.
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 A) cell constraint. B) density-dependent inhibition. C) cell division repression. D) growth factor desensitization.
B) density-dependent inhibition.
Sister chromatids are A) found right after a cell divides. B) joined together at a centromere. C) made only of DNA. D) unique to prokaryotes.
B) joined together at a centromere.
During which phase of mitosis do the chromosomes line up on a plane equidistant from the two spindle poles? A) prophase B) metaphase C) anaphase D) telophase
B) metaphase
The phase of mitosis during which the mitotic spindle begins to form is A) interphase. B) prophase. C) metaphase. D) anaphase.
B) prophase.
Which of the following helps maintain the structure of chromosomes and control the activity of genes? A) the nuclear membrane B) proteins C) centromeres D) ribosomes
B) proteins
Which of the following statements is false? A) Gametes are haploid cells. B) Two haploid cells fuse during fertilization. C) An X chromosome is an autosome. D) A zygote is a fertilized egg.
C) An X chromosome is an autosome.
Which of the following statements regarding mitosis and meiosis is false? A) Meiosis only occurs in the ovaries and testes. B) All sexual life cycles involve an alternation of diploid and haploid stages. C) Mitosis produces daughter cells with half the number of chromosomes as the parent cell. D) A normal human zygote has 46 chromosomes.
C) Mitosis produces daughter cells with half the number of chromosomes as the parent cell.
Which of the following features likely accounts for the difference between plant and animal cell cytokinesis? A) Animal cells lack the microfilaments required for forming a cleavage furrow. B) Animal cells lack chloroplasts. C) Plant cells have cell walls. D) Plant cells have two sets of chromosomes; animal cells have one set of chromosomes.
C) Plant cells have cell walls.
Strictly speaking, the phrase "like begets like" refers to A) all forms of reproduction. B) sexual reproduction only. C) asexual reproduction only. D) production of gametes from a premeiotic cell.
C) asexual reproduction only.
Which of the following occurs during interphase? A) a reduction in the size of the nuclear membrane B) cytokinesis C) cell growth and duplication of the chromosomes D) separation of newly formed DNA to opposite ends of the cell
C) cell growth and duplication of the chromosomes
A benign tumor differs from a malignant tumor in that a benign tumor A) is cancerous. B) spreads from the original site. C) does not metastasize. D) never causes health problems.
C) does not metastasize.
The genetic material is duplicated during A) the mitotic phase. B) G1. C) the S phase. D) G2.
C) the S phase.
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 of the following statements regarding cell division is false? A) Cell division can reproduce an entire organism. B) Cell division is necessary for development to occur. C) Cell division is the basis of both sexual and asexual reproduction. D) Cell division is common in eukaryotes but rare in prokaryotes.
D) Cell division is common in eukaryotes but rare in prokaryotes.
Which of the following statements regarding sexual and asexual reproduction is true? A) Cell division only occurs after sexual reproduction. B) Only offspring from asexual reproduction inherit traits from two parents. C) Sexual reproduction typically includes the development of unfertilized eggs. D) Sexual reproduction is more likely to increase genetic variation than is asexual reproduction.
D) Sexual reproduction is more likely to increase genetic variation than is asexual reproduction.
Which of the following statements regarding the cell cycle control system is false? A) The cell cycle control system receives messages from outside the cell that influence cell division. B) The cell cycle control system triggers and controls major events in the cell cycle. C) The cell cycle control system includes three key checkpoints to complete a cell cycle. D) The cell cycle control system operates independently of the growth factors.
D) The cell cycle control system operates independently of the growth factors.
With the exception of identical twins, siblings who have the same two biological parents are likely to look similar, but not identical, to each other because they have A) identical chromosomes but different genes. B) identical genes but different chromosomes. C) the same combination of traits but different genes. D) a similar but not identical combination of genes.
D) a similar but not identical combination of genes.
Eukaryotic chromosomes differ from prokaryotic chromosomes in that they A) are simpler. B) are circular in structure. C) include fewer proteins. D) are housed in a membrane-enclosed nucleus.
D) are housed in a membrane-enclosed nucleus.
Mature human nerve cells and muscle cells A) become cancerous more easily than other cell types. B) continue to divide throughout their lifetime. C) are permanently in a state of nondivision. D) cease dividing after a predetermined number of cell generations.
D) cease dividing after a predetermined number of cell generations.
Which of the following is probably the main factor responsible for the phenomenon of density-dependent inhibition? A) a local accumulation of growth-inhibiting factors B) cells' innate ability to "sense" when the organ of which they are a part has no need for additional cells C) a local deficiency of nutrients D) physical contact of cell-surface proteins between adjacent cells
D) physical contact of cell-surface proteins between adjacent cells
Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called A) chromatin. B) sister chromosomes. C) nucleoli. D) sister chromatids.
D) sister chromatids.
During which phase of mitosis does the nuclear envelope re-form? A) anaphase B) metaphase C) prophase D) telophase
D) telophase
Which of the following statements correctly describes the timing of DNA synthesis?
DNA is synthesized in the S phase of interphase.
The first step of bacterial replication is _____.
DNA replication
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.
When examining cells in the laboratory, you notice that a particular cell has half as much DNA as the surrounding cells. This observation can be explained if 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 cell cycle sequence of events for these reactivated cells?
G1, S, G2, M
You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?
In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.
Nucleoli are present during _____.
Interphase
During binary fission, each copy of the duplicating chromosome moves to opposite ends of the cell. What does this achieve?
It ensures that each daughter cell receives one copy of the chromosome.
The chromosomes line up in the center of the cell during which phase of mitosis?
Metaphase
The likelihood of death within twenty years of a diagnosis for DCIS (ductal carcinoma in situ, a type of breast cancer) is only 3.3%. Does this mean that every individual diagnosed with DCIS has a 3.3% chance of death within twenty years from the disease?
No. Individuals within certain risk groups (such as women under age 40) have a risk notably higher than 3.3%, whereas individuals not in these risk groups have a lower risk on average.
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 functional within any given cell, regardless of the total number of X chromosomes.
The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
Prophase
Crossing over occurs during _____.
Prophase I
Synapsis occurs during _____.
Prophase I
During _____ a spindle forms in a haploid cell.
Prophase II
Which of the following is a key difference between meiosis and mitosis?
Synapsis occurs.
The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
Telophase
What must happen before a cell can begin mitosis?
The chromosomes must be duplicated.
What would be the immediate consequence of destroying a cell's centrosomes?
The mitotic spindle would not form.
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
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.
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?
XO
Which of the following represents a chromosomally normal human female?
XX
Crossing over is important because it __________.
allows the exchange of genes between homologous chromosomes
If a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction, the resulting chromosomal abnormality is called _____.
an inversion
Centromeres divide and sister chromatids become full-fledged chromosomes during _____.
anaphase
The stage of mitosis during which the chromosomes move toward separate poles of the cell is _____.
anaphase
Homologous chromosomes migrate to opposite poles during _____.
anaphase I
During _____ sister chromatids separate.
anaphase II
A cell replicates its entire chromosomal DNA only __________.
before it is about to divide
Bacteria divide by:
binary fission
Asexual and sexual reproduction differ in that sexual reproduction _____.
can produce great variation among the offspring
Meiosis differs from mitosis in that _____ only occurs in meiosis.
crossing over
At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.
cytokinesis
In bacterial cells, binary fission involves __________.
distribution of a copy of the single parental chromosome to each daughter cell
when are cells haploid?
end of meiosis 1 and 2
True or false. Mitosis takes place during M phase of the cell cycle, which is longer than interphase.
false; Mitosis does indeed take place during M phase, but M phase is shorter than interphase; cells spend most of their time in interphase.
Consider the photograph shown below. You can determine this is a plant cell rather than an animal cell because it has __________.
formed a cell plate
Meiosis II typically produces _____ cells, each of which is _____.
four ... haploid
The function of meiosis is to make __________.
four cells with a haploid number of chromosomes
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.
During asexual reproduction, yeast cells can produce _____.
genetically identical offspring
Fertilization joins _____ to produce a _____.
haploid gametes ... diploid zygote
During anaphase I, __________.
homologous chromosomes separate and migrate toward opposite poles
During prophase I of meiosis,
homologous chromosomes stick together in pairs.
Chromatids are _____.
identical copies of each other if they are part of the same chromosome
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 some organisms such as certain fungi and algae, cells undergo mitosis repeatedly without subsequently undergoing cytokinesis. What would be the consequence of this?
large cells containing many nuclei
Gametes are produced by _____.
meiosis
If it weren't for _____, chromosome number would double with every generation of sexual reproduction.
meiosis
Variation occurs when chromosomes are shuffled in _____.
meiosis
During _____ chromosomes align single file along the equator of a haploid cell.
metaphase II
Looking through a light microscope at a cell undergoing division, you see that the condensed chromosomes have lined up along the midline of the cell. The homologous pairs are NOT joined in tetrads. Each chromosome takes its own place in line, independentof its homolog. You are witnessing _____.
metaphase of mitosis
Which of the following is a correct representation of an event that occurs in mitosis?
metaphase—chromosomes line up on the equatorial plane.
After fertilization, the resulting zygote begins to divide by __________.
mitosis
During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____.
nondisjunction
Duplication of the chromosomes to produce sister chromatids _____.
occurs in both mitosis and meiosis
The term binary fission is best applied to _____.
prokaryotes
Spindle fibers attach to kinetochores during _____.
prometaphase
Chromosomes become visible during _____.
prophase
The correct order of events during meiosis is
prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.
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.
Which processes lead to most genetic variation in sexually reproducing organisms?
random fertilization,independent orientation of chromosomes in meiosis,crossing over
The exchange of parts between nonhomologous chromosomes is called _____.
reciprocal translocation
During anaphase II, __________.
sister chromatids separate and migrate toward opposite poles
An example of a cell that is 2n is a __________.
somatic cell
Mitosis occurs in _____; meiosis occurs in _____.
somatic or body cells ... germ cells in the testes or ovaries
Cytokinesis often, but not always, accompanies _____.
telophase
At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.
telophase I
At the end of _____ and cytokinesis there are four haploid cells.
telophase II
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, whether the DNA is linear or circular
Crossing over is _____.
the exchange of homologous portions of nonsister chromatids
Meiosis I produces _____ cells, each of which is _____.
two ... haploid
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
Homologous chromosomes possess the same genes arranged in the same order but may possess different __________ of some of these genes.
versions
