Exam 3 Ch 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
How many pairs of autosomes do humans have?
22 pairs
In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing __________ different gametes.
2^23
A human somatic cell contains __________ chromosomes.
46
In a cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.
5
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
Imagine that a human skin cell went through mitosis but did not undergo cytokinesis. How many chromosomes would be in the cell?
92
What is the difference between a benign tumor and a malignant tumor?
Benign tumors do not metastasize; malignant tumors do.
During meiosis I, homologous chromosomes form a tetrad and crossing over occurs. What is the outcome of crossing over?
Crossing over creates new combinations of genes present on a single chromosome.
Which of the following statements correctly describes the timing of DNA synthesis?
DNA is synthesized in the S phase of interphase.
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.
Crossing over occurs during _____.
Prophase I
Synapsis occurs during _____.
Prophase I
DNA replication occurs in _____.
S phase of interphase
During anaphase II, __________.
Sister chromatids separate and migrate toward opposite poles.
Which of the following is a key difference between meiosis and mitosis?
Synapsis occurs.
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.
During cell division, what role do centrosomes play?
They organize the microtubules.
Which of the following occurs during mitosis?
Two daughter nuclei, one at each pole of the cell, are generated.
Which of the following represents a chromosomally normal human female?
XX
Crossing over is important because it __________.
allows the exchange of different versions of genes between homologous chromosomes
The stage of mitosis during which the chromosomes move toward separate poles of the cell is _____.
anaphase
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
A cell replicates its entire chromosomal DNA only __________.
before it is about to divide
Asexual and sexual reproduction differ in that sexual reproduction _____.
can produce great variation among the offspring
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
In the picture below, the chromosomal region where the nonsister chromatids are crossing over is called a(n) _____.
chiasma
Meiosis differs from mitosis in that _____ only occurs in meiosis.
crossing over
A cleavage furrow forms in an animal cell during _____.
cytokinesis
The diploid phase of the human life cycle begins with _____.
fertilization
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
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
At the conclusion of meiosis I, the daughter cells are _____.
haploid and the sister chromatids are joined
During anaphase I, __________.
homologous chromosomes move to opposite poles
In anaphase I, __________.
homologous chromosomes move toward opposite poles
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
Variation occurs when chromosomes are shuffled in _____.
meiosis
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
Asexual reproduction _____.
produces offspring genetically identical to the parent
In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.
prophase
Which of the following shows mitosis in the correct chronological order?
prophase, prometaphase, metaphase, anaphase, telophase
One version of a gene may encode __________, whereas a different version of the same gene may encode __________.
red eyes; white eyes
In meiosis II, _____.
sister chromatids separate
The kinetochores are __________.
sites at which microtubules attach to chromosomes
An example of a cell that is 2n is a __________.
somatic cell
Crossing over is _____.
the exchange of homologous portions of nonsister chromatids
During mitosis, the chromosomes move because _____.
they attach to a dynamic, precisely regulated mitotic spindle
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
Homologous chromosomes possess the same genes arranged in the same order but may possess different __________ of some of these genes.
versions