Biology Ch. 8
What is the difference between a benign tumor and a malignant tumor?
Benign tumors do not metastasize; malignant tumors do.
Which of the following occurs during mitosis?
Chromatids separate.
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.
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
Which of the following is a key difference between meiosis and mitosis?
Synapsis occurs.
Which event occurs only during prophase I of the first meiotic division?
Synapsis of homologous pairs occurs.
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.
Chromatids are _____.
identical copies of each other if they are part of the same chromosome
When we say that an organism is haploid, we mean that _____.
its cells each have one set of chromosomes
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
In humans, the _____ determines the sex of the offspring because _____.
male ... the male can contribute either an X or a Y chromosome
Variation occurs when chromosomes are shuffled in _____.
meiosis
At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?
metaphase
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
Down syndrome can be the result of _____.
nondisjunction of chromosome 21 during meiosis
The term binary fission is best applied to _____.
prokaryotes
At which point do centrosomes begin to move apart to the opposite poles of the cell in a dividing human liver cell?
prophase
In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.
prophase
Crossing over occurs during _____.
prophase I
Synapsis occurs during _____.
prophase I
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
At a critical point in meiosis, the chromosomes do not replicate. This occurs between _____.
telophase I and prophase II
Chromatids form during _____.
the S phase of interphase
DNA replication occurs in _____.
the S phase of interphase
One event occurring during prophase is _____.
the beginning of the formation of the 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
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
During anaphase I, _____.
homologues separate and migrate toward opposite poles
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
How many pairs of autosomes do humans have?
22
In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing _____ different gametes.
2^23
Each 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
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. There are _____ chromatids.
92
Which of the following indicates Turner syndrome?
XO
Which of the following is a normal human female?
XX
Consider the photograph of a karyotype. This is _____.
a photograph of all a person's chromosomes
Crossing over is important because it _____.
allows the exchange of genes between homologous chromosomes
Unless the chromosomes were stained to show band patterns, a karyotype would usually be unable to show _____.
an inversion
The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____.
anaphase
Single sister chromatids are found in cells at mitotic _____.
anaphase and telophase
A cleavage furrow forms in an animal cell during _____.
cytokinesis
The function of mitosis is to produce daughter cells that _____.
are genetically identical to the parent cell (assuming no mutation has occurred)
Which of the following conditions would result in inhibition of cell division due to density-dependent factors?
being completely surrounded by other cells
In the picture below, the chromosomal region where the nonsister chromatids are crossing over is called a(n) _____.
chiasma
In bacterial cells, binary fission involves _____.
distribution of a copy of the single parental chromosome to each daughter cell
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
The diploid phase of the human life cycle begins with _____.
fertilization
Cytochalasin B is a chemical that disrupts microfilament formation. This chemical would interfere with _____.
formation of a cleavage furrow
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
An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis?
four
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
During asexual reproduction, yeast cells can produce _____
genetically identical offspring
Consider the two mice shown below. They have the same chromosomes, carrying genes for the same traits in the same loci, but specifying different versions of the same traits—for example, coat and eye color. These chromosomes are called _____.
homologous chromosomes
In anaphase I, _____.
homologous chromosomes move toward opposite poles
