Biology 112 Chapters 12-14
a. non-dividing cells exit cell cycle b. at this point, cell commits to go through the cycle c. DNA replicates d. two centrosomes have formed e. mitotic spindle begins to form f. cell divides, forming two daughter cells
Label each appropriate target
two... haploid
Meiosis I produces _____ cells, each of which is _____.
1 AB : 1 aB
In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?
prometaphase
Spindle fibers attach to kinetochores during _____.
in the S phase
Students in a biology lab isolated cells in various phases of the cell cycle. A population of cells that have 1 1/2 times the DNA of G1 phase cells was most likely isolated from which of the following parts of the cell cycle?
They have different sequences of DNA nucleotides
What makes alleles different from each other?
C and D
Which of these cells is (are) haploid?
ttpp
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?
sister chromatids separate during anaphase
Meiosis II is similar to mitosis in that
four... haploid
Meiosis II typically produces _____ cells, each of which is _____.
23
Normal human gametes carry _____ chromosomes.
prophase I
Synapsis occurs during _____.
1. lengthen 2. lengthen, shorten 3. disassemble
1. During prophase, the microtubules of the mitotic spindle ________. 2. During anaphase, the nonkinetochore microtubules ________ and move past each other, and the kinetochore microtubules _______. 3. During telophase, the nonkinetochore microtubules _______.
dihybrid
A cross between two individuals that are heterozygous for eye and skin color would be an example of a _____ cross.
16 (16 is half of 32)
A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
92
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?
a sperm
A human cell containing 22 autosomes and a Y chromosome is
III only
Amount of DNA per nucleus over the cell division cycle. Which numbered regions of the accompanying figure represent the DNA content associated with cells at metaphase?
telophase II
At the end of _____ and cytokinesis there are four haploid cells.
telophase I
At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.
32
Beginning with a fertilized egg (zygote), how many cells will be present in the embryo following five rounds of cell division?
G1
Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in
anaphase
Centromeres divide and sister chromatids become full-fledged chromosomes during _____.
nonsister chromatids of homologous chromosomes
Crossing over, resulting in an increase in genetic variation, occurs between _____.
1. DNA nucleotides 2. locus 3. homologous pairs 4. twice 5. alleles 6. genes
Every gene is a sequence of (1) at a specific position along a chromosome called a (2). Diploid cells have two sets of chromosomes, one set inherited from each parent, that form (3). The homologs of a chromosome pair contain the same genetic loci. Therefore, each genetic locus is represented (4) in a diploid cell. Variations in inherited characteristics is due to the presence of (5), which are alternative versions of (6).
anaphase I
Homologous chromosomes migrate to opposite poles during _____.
anaphase
In which phase of mitosis do the sister chromatids become daughter chromosomes?
True
True or false? The same phenotype can be produced by more than one genotype.
an alternative version of a gene
What is an allele?
It describes the inheritance of different genes relative to one another.
Which of the following statements about the law of independent assortment is correct?
Traits can be dominant or recessive, and the recessive traits were "hidden" by the dominant ones in the F1.
Which of the following statements correctly describes how Mendel accounted for the observation that traits had disappeared in the F1 generation and then reappeared in the F2 generation?
B, C, F, and G
Which of these gametes contain one or more recombinant chromosomes?
the cell has 18 total chromosomes in 6 sets
A triploid cell contains three sets of homologous chromosomes. Which of the following describes the chromosomes in a triploid cell where n=6? - The cell has 24 sister chromatids when in prophase I. - The cell has 12 total chromosomes at the end of mitosis. - The cell has 3 homologous pairs of chromosomes at the beginning of mitosis. - The cell has 18 total chromosomes in 6 sets.
metaphase I
Homologous pairs of chromosomes are lined up independently of other such pairs during _____.
2-3
In human gamete production there is an average of _____ crossover events per chromosome pair.
shortening of microtubules
Movement of the chromosomes during anaphase would be most directly affected by a drug that prevents which of the following events?
interphase
Nucleoli are present during _____.
II
Which chromosomal configuration would be observed at prometaphase of mitosis?
It is homozygous at two loci
Which of the following is true about a plant with the genotype AABbcc?
The law of independent assortment describes the behavior of two or more genes relative to one another
Which of the following statements about independent assortment or segregation is correct?
1. sister chromatid(s) 2. centromere(s) 3. kinetochore(s) 4. interphase 5. mitotic spindle(s) 6. chromatin 7. cytokinesis 8. centrosome(s)
1. DNA replication produces two identical DNA molecules, called _______, which separate during mitosis. 2. After chromosomes condense, the ________ is the region where the identical DNA molecules are most tightly attached to each other. 3. During mitosis, microtubules attach to chromosomes at the _______. 4. In dividing cells, most of the cell's growth occurs during _______. 5. The _________ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division. 6. During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called _______. 7. In most eukaryotes, division of the nucleus is followed by _______, when the rest of the cell divides. 8. The ________ are the organizing centers for microtubules involved in separating chromosomes during mitosis.
it produces gametes with 23 chromosomes
A particular organism has 46 chromosomes in its karyotype. Which of the following statements is correct regarding this organism? - It reproduces asexually. - It produces gametes with 23 chromosomes. - It must be an animal. - It must be human.
both parents are heterozygous for both genes
A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.
- The chromosomes of one color make up a haploid set. - All red and blue chromosomes together make up a diploid set.
Choose the makeup of a haploid set and a diploid set in this cell. - The chromosomes of one color make up a diploid set. - Blue chromosomes make up a diploid set. - All red and blue chromosomes together make up a haploid set. - The chromosomes of one color make up a haploid set. - Red chromosomes make up a diploid set. - All red and blue chromosomes together make up a diploid set. - According to the picture, a diploid set and a haploid set cannot be identified.
prophase
Chromosomes become visible during _____.
1. sister chromatids 2. sister chromatid cohesion 3. centromere 4. chiasma 5. homologous pair 6. chromosome (duplicated) 7. gene loci 8. nonsister chromatids 9. kinetochore
Label the appropriate structures on this diagram with the following terms:
this cell is diploid
Look at the cell in the figure. Based on this figure, which of the following statements is true? - This cell is haploid. - It is impossible to tell whether the cell is haploid or diploid. - This cell is diploid.
fertilization combines chromosomes from each parent into resulting zygote
Many diploid organisms produce haploid gametes for reproduction. Which of the following best describes how the diploid number of chromosomes is restored in the offspring of these organisms? - DNA replication creates homologous chromosomes - independent assortment in meiosis allows random combinations of chromosomes - synapsis during prophase of meiosis I creates random combinations of alleles - fertilization combines chromosomes from each parent into resulting zygote
S: DNA replication M: cell growth stops and the cell divides G0: A cell's non-dividing stage G1: Cell growth and increase in energy production G2: cell growth and preparation for division
Match each cell cycle phase to what happens in that phase.
alignment of pairs of homologous chromosomes along the middle of the cell
Mendel's law of independent assortment has its basis in which of the following events of meiosis I?
Meiosis produces daughter cells with half the number of chromosome sets of the parent cell; therefore, the parent cell must be diploid.
Mitosis can occur in both haploid and diploid cells, but meiosis can only occur in diploid cells. Why?
DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.
Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?
telophase
daughter nuclei are forming. Cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.
prometaphase
discrete chromosomes are now visible; each consists of two aligned, identical sister chromatids. Later the nuclear envelope will fragment.
anaphase
the chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore microtubules shorten.
prophase
the chromosomes are condensing and the nucleolus is beginning to disappear. The mitotic spindle is starting to form.
infection causes lymphocytes to divide more rapidly
A research team used a culture of lymphocytes with radioactively labeled T nucleotides to study the cell cycle. They found that the lymphocytes incorporated the labeled nucleotide at a significantly higher rate after a pathogen was introduced into the culture. Which of the following conclusions is most consistent with the results?
HT
A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
I and V
Amount of DNA per nucleus over the cell division cycle. G1 is represented by which numbered part(s) of the cell division cycle in the accompanying figure?
II
Amount of DNA per nucleus over the cell division cycle. Which region of the accompanying figure represents S phase?
1. yes 2. yes 3. no
Consider three questions concerning the animal cell that has been treated with the inhibitor. 1. Will this cell elongate during mitosis? 2. Will the sister chromatids separate from each other? 3. Will the chromosomes move to the poles of the cell?
telophase
Cytokinesis often, but not always, accompanies _____.
Mitosis - End result is two diploid cells that are genetically identical to each other and the parent cell - A single division occurs, separating sister chromatids - Duplicated chromosomes line up individually on the metaphase plate in a diploid cell Meiosis - Homologous chromosomes pair up and form chiasmata - End result is four haploid cells that are genetically different from each other and the parent cell - Daughter cells contain recombinant chromosomes - The first division separates homologous pairs; the second division separates sister chromatids - Homologous pairs of chromosomes line up on the metaphase plate Both Mitosis and Meiosis - Process starts with a diploid cell - Chromosomes duplicate during interphase
Determine which events occur in mitosis, meiosis, or in both mitosis and meiosis. - End result is two diploid cells that are genetically identical to each other and the parent cell - Homologous chromosomes pair up and form chiasmata - A single division occurs, separating sister chromatids - Duplicated chromosomes line up individually on the metaphase plate in a diploid cell - Process starts with a diploid cell - Chromosomes duplicate during interphase - End result is four haploid cells that are genetically different from each other and the parent cell - Daughter cells contain recombinant chromosomes - The first division separates homologous pairs; the second division separates sister chromatids - Homologous pairs of chromosomes line up on the metaphase plate
1. False 2. False 3. False 4. True 5. True
Determine which statements are true and which are false. 1. The second division of meiosis reduces the number of chromosomes in each cell by half. 2. Meiosis occurs in both somatic (body) cells and sex cells. 3. Crossing over and synapsis occur after the homologous chromosomes separate in meiosis I. 4. In meiosis II, the daughter cells from meiosis I undergo a very similar division to mitosis. 5. The first division of meiosis reduces the number of chromosomes in each cell by half.
prophase II
During _____ a spindle forms in a haploid cell.
the mitotic phase
During _____ both the contents of the nucleus and the cytoplasm are divided.
metaphase II
During _____ chromosomes align single file along the equator of a haploid cell.
anaphase II
During _____ sister chromatids separate.
interphase
During _____ the cell grows and replicates both its organelles and its chromosomes.
meiosis I, anaphase
During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur?
These homologous chromosomes represent a materna and a paternal chromosome
Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosomes is correct? - Each of these homologous chromosomes consists of a single chromatid. Therefore, they must come from a haploid cell. - These homologous chromosomes represent a maternal and a paternal chromosome. - These homologous chromosomes are formed by DNA replication.
1. meiosis 2. homologous chromosomes 3. crossing over
How can you tell that the cell in the figure below is undergoing meiosis, not mitosis? This cell must be undergoing (1) because the two (2) are associated with each other at the metaphase plate. Also, chiasmata are clearly present meaning that (3) has occurred, another process unique to this type of cell division.
meiosis
Human gametes are produced by _____.
1. prophase 2. prometaphase 3. metaphase 4. anaphase 5. interphase
Identify a cell in each of the following stages:
metaphase I
Identify the stage of meiosis shown.
16
If a cell at metaphase of mitosis contains 32 sister chromatids, how many chromosomes will be present in a G1 cell?
none
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?
2x
If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I will be
x
If the DNA content of a diploid cell is x in the G1 phase of the cell cycle and 2x at metaphase of meiosis I, then the DNA content of the same cell at metaphase of meiosis II will be
segregation of daughter chromosomes
If the cell whose nuclear material is shown in the accompanying figure continues toward completion of mitosis, which of the following events would occur next?
1. asexual reproduction 2. genetic clone 3. no genetic variability 4. sexual reproduction 5. unique offspring 6. crossing over 7. genetic variability
In (1), the sole parent gives rise to the (2) via mitosis without the fusion of gametes. Thus, there is (3). In (4), two parents give rise to a (5) because of (6). Thus, there is (7). This will confer selective advantages or disadvantages on different individuals and will drive evolution in adverse environmental changes.
16
In a diploid cell with four chromosome pairs (2n = 8), how many sister chromatids will be found in a nucleus at prophase of mitosis?
roan x roan
In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (CRCW) offspring of red (CRCR) and white (CWCW) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?
P ... F1 ... F2
In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations?
cells with more than one nucleus
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
Mutation in the p53 gene - Cell receives go-ahead signal at the G1 checkpoint and most likely finishes the cell cycle with damaged DNA. Mutation in the RB gene - Cell receives go-ahead signal at the G1 checkpoint, entering the S phase regardless of whether conditions are good for growth. Mutation in the MAD gene - Cell receives go-ahead signal at the M checkpoint and daughter cells may end up with extra or missing chromosomes.
Mutations in tumor-suppressor genes can lead to an out-of-control cell cycle and cancer development. What would be the consequence of a mutation in each tumor-suppressor gene? - Cell receives go-ahead signal at the G1 checkpoint and most likely finishes the cell cycle with damaged DNA. - Cell receives go-ahead signal at the G1 checkpoint, entering the S phase regardless of whether conditions are good for growth. - Cell receives go-ahead signal at the M checkpoint and daughter cells may end up with extra or missing chromosomes.
Prophase - Cohesins join sister chromatids of duplicated chromosome. - Tubulins assemble into spindle microtubules. Prometaphase - Microtubules attach to kinetochores. Metaphase - Kinetochores are motionless in relation to poles of cell. Anaphase - Kinetochores move toward poles of cell. - Cohesins break down. Telophase - Spindle microtubules disassemble.
Sort each process into the appropriate bin to indicate the stage of mitosis in which it occurs. - Cohesins join sister chromatids of duplicated chromosome. - Tubulins assemble into spindle microtubules. - Microtubules attach to kinetochores. - Kinetochores are motionless in relation to poles of cell. - Kinetochores move toward poles of cell. - Cohesins break down. - Spindle microtubules disassemble.
At the completion of mitosis and cytokinesis, the daughter cells could have missing or extra chromosomes.
The M checkpoint is an example of a checkpoint that is internally controlled by the cell. What would be the potential consequence seen in daughter cells if the cell received a stop signal at this checkpoint but was able to continue to anaphase anyway?
During mitosis, each chromatid of a duplicated chromosome becomes attached to the microtubule of one of the mitotic spindles. At anaphase, mitotic spindles pull the chromatids toward the poles of the cell, therefore forming two identical chromosomal sets at each pole.
The continuity of life is based on heritable information in the form of DNADNA. How does the process of mitosis faithfully parcel out exact copies of this heritable information in the production of genetically identical daughter cells?
1. segregation 2. diploid 3. meiosis 4. 3:1 5. monohybrids 6. heterozygous 7. dominant 8. recessive 9. homozygous 10. independent assortment 11. 9:3:3:1 12. dihybrids
The law of (1) states that genes have alternative forms, or alleles. In a (2) organism, the two alleles of a gene separate during (3) and gamete formation; each sperm or egg carries only one allele of each pair. This law explains the (4) ratio of the F2 phenotypes observed when (5) self-pollinate. Each organism inherits one allele for each gene from each parent. In (6) individuals, the two alleles are different, and the expression of the (7) allele masks the phenotypic effect of the (8) allele. In (9) individuals, the two alleles are identical. The law of (10) states that the pair of alleles for a given gene segregates into gametes independently of the pair of alleles for any other gene. This law explains the (11) ratio of the F2 phenotypes in a cross between (12)
1. false 2. true 3. true 4. false 5. true
The timing and rate of cell division is crucial to normal growth, development, and maintenance of an organism. Which of the following statements about the cell cycle control system are true? 1. If a cell does not receive a go-ahead signal at the G1 checkpoint, the cell leaves the cell cycle and dies. 2. Signals that regulate the cell cycle come from outside and inside the cell. 3. Most cells that pass the G1 checkpoint ultimately complete the cell cycle. 4. Cells move freely through the cell cycle unless they receive a stop signal at a checkpoint when something is wrong. 5. The M checkpoint occurs during prometaphase of mitosis to ensure that all chromosomes are attached to spindles by both kinetochores.
1. True 2. False 3. True 4. True
True or False 1. For crossing over to occur, homologous chromosomes must align precisely early in prophase I so that nonsister chromatids can exchange corresponding segments of DNA. 2. Crossing over prevents homologous chromosomes from separating during meiosis I. 3. As a result of crossing over, sister chromatids are no longer identical to each other. 4. Crossing over occurs at the ends of chromosomes, rather than near the centromeres.
False
True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.
25%
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
one long DNA molecule, associated with many proteins
What is the best description of the structure of a chromosome in the nucleus of a non-dividing cell?
the cell is diploid because it contains two sets of chromosomes
What is the best evidence telling you whether this cell is diploid or haploid?
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
What is the difference between heterozygous and homozygous individuals?
44 autosomes and 2 sex chromosomes
What number and types of chromosomes are found in a human somatic cell?
Traits are inherited in discrete units and are not the result of "blending"
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
gametes, progeny
When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.
A? x aa
Which of these is a testcross? A? x A? A? x Aa aa x aa A? x AA A? x aa
E
Which of these phases encompasses all of the stages of mitosis but no other events?
V
Which chromosomal configuration would be observed in one daughter cell after telophase of mitosis?
the exchange of homologous portions of nonsister chromatids
Which of the following answers describes the phenomenon of crossing over in meiosis?
- To allow cells to respond to cues from their internal state and from their environment. - To make sure daughter cells end up with the right number of chromosomes. - To make sure cells only divide when conditions are favorable for growth and development of the organism
Which of the following are reasons the cell cycle must be regulated? Select all that apply - To allow cells to respond to cues from their internal state and from their environment. - To make sure daughter cells end up with the right number of chromosomes. - To make sure daughter cells are genetically different from the parent cell. - To make sure cells only divide when conditions are favorable for growth and development of the organism
the inheritance of a particular copy of one chromosome does not affect the inheritance of a different chromosome
Which of the following best describes how an individual with genotype AaBbCCDdEE can make gametes with eight different genotypes. - mutations during meiosis form new alleles that are incorporated into the gametes - dominant alleles tend to be inherited together - crossing over during prophase I leads to increased genetic diversity - the inheritance of a particular copy of one chromosome does not affect the inheritance of a different chromosome
synapsis occurs
Which of the following occurs during meiosis, but not during mitosis? - chromosomes align at the metaphase plate - a spindle apparatus forms - chromosomes condense - synapsis occurs - chromosomes migrate to opposite poles
In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring
Which of the following statements about reproduction is correct? - In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring. - Asexual reproduction produces only haploid offspring. - Asexual reproduction, but not sexual reproduction, is characteristic of only plants and fungi. - In asexual reproduction, offspring are produced by fertilization without meiosis.
Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.
Which of the following statements correctly describes how sister chromatids and homologous chromosomes differ from each other? - Homologous chromosomes are closely associated with each other in both mitosis and meiosis. Sister chromatids are only associated with each other during mitosis. - Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication. - They are not different.; homologous chromosomes and sister chromatids are both identical copies of each other. - Homologous chromosomes are identical copies of each other. One sister chromatid comes from the father, and one comes from the mother. - Sister chromatids are only formed during mitosis. Homologous chromosomes are formed during meiosis.
All of the genes controlling the traits behaved as if they were on different chromosomes
Which of the following statements correctly explains the fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment?
A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.
Which of the following statements is correct in describing the terms monohybrid cross and dihybrid cross? - A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations. - A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio. - A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents. - A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.
each diploid cell has eight homologous pairs of chromosomes
Which of the following statements is true of a species that has a chromosome number of 2n = 16? - The species has 16 sets of chromosomes per cell. - Each diploid cell has eight homologous pairs of chromosomes. - A gamete from this species has four chromosomes. - The species is diploid and has 32 chromosomes per cell.
1/2
kin color in a certain species of fish is inherited via a single gene with four different alleles. One fish of this type has alleles 1 and 3 (S1S3) and its mate has alleles 2 and 4 (S2S4). If each allele confers a unit of color darkness such that S1 has one unit, S2 has two units, and so on, then what proportion of their offspring would be expected to have five units of color?
metaphase
the spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the plate.
