1.
There are a number of differences between fission of a bacterium and human cell division. Which of the following is not one of them?
Correct Answer
D. Bacteria have to duplicate their DNA before dividing; human cells do not
Explanation
The statement "Bacteria have to duplicate their DNA before dividing; human cells do not" is not a difference between fission of a bacterium and human cell division. Both bacteria and human cells need to duplicate their DNA before dividing. This is a crucial step in the process of cell division to ensure that each daughter cell receives a complete set of genetic information.
2.
You would be unlikely to see which of the following human cells dividing?
Correct Answer
A. Muscle cell
Explanation
Muscle cells, also known as muscle fibers, are specialized cells that make up muscle tissue. Unlike other types of cells, such as skin cells, cancer cells, cells from an embryo, and intestinal lining cells, muscle cells have a unique characteristic of being multinucleated. This means that they have multiple nuclei within a single cell, which is a result of the fusion of multiple myoblasts during development. Due to this multinucleated nature, muscle cells do not undergo typical cell division, known as mitosis, making it unlikely to see them dividing.
3.
Which of the following correctly matches a phase of the cell cycle with its description?
Correct Answer
D. G1- immeadiately follows cell division
Explanation
The correct answer is G1- immediately follows cell division. The cell cycle consists of several phases, including G1, S, G2, and M. G1 is the first gap phase, which occurs immediately after cell division. During this phase, the cell grows in size and prepares for DNA replication in the S phase. Therefore, G1 immediately follows cell division.
4.
In telophase of mitosis, the miotic spindle breaks down and nuclear membranes form. This is essentially the opposite of what happens in
Correct Answer
A. PropHase
Explanation
In prophase of mitosis, the nuclear membrane breaks down and the miotic spindle begins to form. This is the opposite of what happens in telophase, where the miotic spindle breaks down and nuclear membranes form.
5.
Sister Chromatids
Correct Answer
C. Are produced during s pHase between cell division
Explanation
During the S phase of the cell cycle, DNA replication occurs. Sister chromatids are produced during this phase, where each replicated chromosome consists of two identical chromatids held together by a centromere. These sister chromatids are then separated during the first meiotic division, ensuring that each resulting daughter cell receives one copy of each chromosome. Therefore, the correct answer is that sister chromatids are produced during the S phase between cell divisions.
6.
Which of the following is not a function of miotic cell division in animals?
Correct Answer
D. Production of gametes
Explanation
Miotic cell division in animals is responsible for asexual reproduction, growth, repair of damaged organs, and cell replacement. However, the production of gametes is not a function of miotic cell division. Gametes, which are reproductive cells, are produced through a different process called meiosis. Meiosis involves two rounds of cell division and results in the formation of haploid cells with half the number of chromosomes. Therefore, the production of gametes is not a function of miotic cell division.
7.
Meiosis
.
Correct Answer
B. Halves the number of chromosomes in cells
Explanation
Meiosis is the process in which cells undergo two divisions to produce gametes (sperm and eggs). During meiosis, the number of chromosomes in the cells is halved, resulting in haploid cells with half the number of chromosomes as the parent cell. This reduction in chromosome number is important for sexual reproduction, as it ensures that when the gametes combine during fertilization, the resulting offspring will have the correct number of chromosomes. Therefore, the answer "halves the number of chromosomes in cells" accurately describes the process of meiosis.
8.
Crossing over is
.
a)important in genetic recombination
b)what makes a cell become cancerous c) a key process that occurs during mitosis d)an important mechanism of chromosome repair e) what prevents cells from multiplying indefinently in cell culture
Correct Answer
A. Important in genetic recombination
Explanation
Crossing over is an important process in genetic recombination. It involves the exchange of genetic material between homologous chromosomes during meiosis. This exchange results in the creation of new combinations of genes, increasing genetic diversity. Therefore, crossing over plays a crucial role in the generation of genetic variation and is essential for the evolution of species.
9.
Human __ are diploid, and human __ are haploid
.
Correct Answer
C. Somatic cells...gametes
Explanation
Somatic cells in humans are diploid, meaning they have two sets of chromosomes (one set from each parent). On the other hand, gametes (such as sperm and egg cells) are haploid, meaning they have only one set of chromosomes. Therefore, the correct answer is "somatic cells...gametes".
10.
Which of the following does not lead to genetic variability? a)random fertilization
.
b)crossing over during meiosis
c) division of chromosomes during anaphase of mitosis
d) orientation of chromosomes during metaphase 1 of meiosis e) mutation
Correct Answer
C. Division of chromosomes during anapHase of mitosis
Explanation
During anaphase of mitosis, the chromosomes are already replicated and are being separated into two daughter cells. This process does not involve any exchange or rearrangement of genetic material, therefore it does not lead to genetic variability.
11.
Most cells will divide if they receive the proper signal at a checkpoint in the ___ phase of the cell cycle
Correct Answer
B. G1
Explanation
During the G1 phase of the cell cycle, cells undergo growth and prepare for DNA replication. At this checkpoint, cells receive signals from the environment to determine if they are ready to proceed with division. If the proper signal is received, the cells will continue into the S phase to replicate their DNA. Therefore, the correct answer is G1.
12.
Geneticists suspect that the extra chromosome seen in Down syndrome usually comes from the egg, rather than the sperm, because
Correct Answer
E. Meiosis takes longer in the ovary, increasing the likelihood of error
Explanation
Meiosis is the process by which cells divide and produce eggs or sperm. It is known that meiosis takes longer in the ovary compared to the testes. This increased duration provides more opportunities for errors to occur during the division process, such as the incorrect separation of chromosomes. As a result, geneticists suspect that the extra chromosome seen in Down syndrome usually comes from the egg rather than the sperm.
13.
Which of the following chromosomal alterations would you expect to have the most drastic consequences?
Correct Answer
D. Deletion
Explanation
Deletion is the most drastic chromosomal alteration because it involves the loss of a segment of the chromosome. This loss can result in the deletion of important genes or regulatory elements, leading to significant changes in the genetic information. In contrast, inversion, duplication, and translocation may cause disruptions or rearrangements of genetic material, but they do not involve the loss of genetic information like deletion does. Therefore, deletion has the most severe consequences among the given options.
14.
In certain fungae and algae, cells undergo mitosis repeatedly without subsequently undergoing cytokinesis. What would result from this?
a)a decrease in chromosome number b)inability to duplicate DNA c) division of the organism into many cells, most lacking nuclei d)large cells containing many nuclei e)a rapid rate of sexual reproduction
.
Correct Answer
D. Arge cells containing many nuclei
Explanation
When cells undergo mitosis repeatedly without undergoing cytokinesis, it results in the formation of large cells containing many nuclei. This is because mitosis is the process of cell division that results in the formation of two daughter cells, while cytokinesis is the process of dividing the cytoplasm and forming separate cell membranes. Without cytokinesis, the cells continue to replicate their DNA and divide their nuclei through mitosis, but the cytoplasm remains undivided, leading to the formation of cells with multiple nuclei.
15.
Which of the following is the most significant difference between mitosis and meiosis? a)chromosomes are duplicated before mitosis b)Meiosis is not followed by cytokinesis c) Homologous pairs of chromosomes are split up in meiosis
.
d) a spindle formed of microtubules moves the chromosomes in mitosis e)crossing over occurs in mitosis
Correct Answer
C. Homologous pairs of chromosomes are split up in meiosis
Explanation
The most significant difference between mitosis and meiosis is that in meiosis, homologous pairs of chromosomes are split up. This is a crucial step in meiosis that ensures genetic diversity in offspring. In mitosis, chromosomes are duplicated, but they do not undergo the same splitting process as in meiosis. This difference is important because it allows for the formation of gametes with unique combinations of genetic material during meiosis.
16.
If there are 22 chromosomes in the nucleus of a toad skin cell, a toad egg would contain __ chromosomes.
Correct Answer
C. 11
Explanation
The number of chromosomes in an organism's cells is typically halved during the process of meiosis, which occurs during the formation of eggs and sperm. Therefore, if a toad skin cell has 22 chromosomes, a toad egg would contain half of that number, which is 11 chromosomes.
17.
Which of the following carry the same genetic information?
.
a)sister chromatids
b)x and y chromosomes c)all autosomes d)homologous chromosomes e)all haploid cells
Correct Answer
A. Sister chromatids
Explanation
Sister chromatids carry the same genetic information because they are two identical copies of a single chromosome that are produced during DNA replication. They are held together by a structure called the centromere and are separated during cell division.
18.
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 seen in telophase of mitosis?
.
Correct Answer
B. 100 units
Explanation
During the G2 phase of the cell cycle, the cell undergoes DNA replication, resulting in the doubling of the amount of DNA. Therefore, if the grasshopper cells contained 200 units of DNA during the G2 phase, each daughter cell formed during telophase of mitosis would contain half of that amount, which is 100 units.
19.
What would be the quantity of DNA in one of the grasshopper cells (question 6) produced by telophase 2 of meiosis?
.
a)50 units
b)100 units c)between 50 and 100 units d)200 units e)400 units
Correct Answer
A. 50 units
Explanation
During telophase 2 of meiosis, the chromosomes have already separated and are now in separate cells. Each of these cells will have half the amount of DNA as the original cell. Therefore, the quantity of DNA in one of the grasshopper cells produced by telophase 2 of meiosis would be 50 units.
20.
The two chromosomes of a homologous pair a) carry identical genetic information at corresponding locations b) carry information for the same characteristics at different locations c) carry identical genetic information at different locations d) carry information for the same characteristics at corresponding locations e)any of the above is possible.
Correct Answer
D. Carry information for the same characteristics at corresponding locations
Explanation
The correct answer is "carry information for the same characteristics at corresponding locations." This is because homologous chromosomes contain genes that code for the same traits or characteristics, and these genes are located at corresponding positions on each chromosome. Therefore, the chromosomes carry information for the same characteristics at corresponding locations.
21.
A picture of a dividing pigeon cell taken through a microscope shows that the cell contains 7 chromosomes, each consisting of 2 chromatids. This picture might have been taken during
.
a)metaphase of mitosis b)prophase i of meiosis c)telophase 2 of meiosis d)prophase 2 of meiosis e)telophase of mitosis
Correct Answer
D. PropHase 2 of meiosis
Explanation
The picture shows 7 chromosomes, each consisting of 2 chromatids. This indicates that the cell is in the prophase 2 of meiosis. In prophase 2 of meiosis, the chromosomes have already replicated and consist of two sister chromatids. The chromosomes are also condensed and visible under a microscope.
22.
A culture of mouse cells is treated with a chemical that interferes with the activity if microfilaments. Which of the following will probably be affected the most?
a) mitosis b)chromosome duplication c)pairing of homologous chromosomes d) cytokinesis e) joining of sister chromatids at the centromere
.
Correct Answer
D. Cytokinesis
Explanation
The correct answer is cytokinesis. Cytokinesis is the process in which the cytoplasm of a cell is divided into two daughter cells during cell division. Microfilaments play a crucial role in the formation of the contractile ring, which constricts and separates the two daughter cells. Therefore, if the chemical interferes with the activity of microfilaments, it will likely disrupt cytokinesis the most.
23.
A zoologist examined an intestine cell from a crayfish and counted 200 chromosomes, each consisting of 2 chromatids, at prophase 1 of mitosis. What would he expect to see in each of the four cells at telophase 2 of meiosis if he looked in the crayfish ovary?
Correct Answer
D. 100 chromosomes, each consisting of 1 chromatid
Explanation
During prophase 1 of meiosis, the chromosomes replicate to form sister chromatids, resulting in 200 chromosomes, each consisting of 2 chromatids. However, during meiosis, there are two rounds of cell division. At telophase 2 of meiosis, the sister chromatids separate, resulting in four cells with half the number of chromosomes as the original cell. Therefore, each of the four cells would have 100 chromosomes, each consisting of 1 chromatid.
24.
A karyotype would be least likely to show which of the following?
Correct Answer
D. Part of a chromosome turned around
Explanation
A karyotype is a visual representation of an individual's chromosomes, arranged in pairs according to size and shape. It is used to identify abnormalities in the number or structure of chromosomes. In a karyotype, part of a chromosome turned around would not be easily identifiable as it would not change the overall number or size of chromosomes. Therefore, it is least likely to be shown in a karyotype.
25.
If an intestinal cell in a grasshopper contains 24 chromosomes, a grasshopper sperm cell contains __ chromosome
Correct Answer
C. 12
Explanation
During sexual reproduction, the sperm and egg cells combine to form a new individual. In most organisms, including grasshoppers, the sperm and egg cells each contain half the number of chromosomes as the other cells in the body. Since the intestinal cell in the grasshopper contains 24 chromosomes, the sperm cell would contain half that number, which is 12 chromosomes.
26.
A biochemist meausred the amount of DNA in cells growing in the labratory and found that the quantity of DNA in a cell doubled
Correct Answer
C. During the m pHase of the cell cycle
Explanation
During the M phase of the cell cycle, the cell undergoes mitosis, which is the process of cell division. In mitosis, the DNA replicates and then separates into two identical sets, one for each new cell. Therefore, the quantity of DNA in a cell doubles during the M phase of the cell cycle.
27.
Which of the following is not a function of mitosis in humans?
Correct Answer
C. Production of gametes from diploid cells
Explanation
Mitosis is the process of cell division that results in the formation of two identical daughter cells. It is responsible for various functions in humans, such as repair of wounds, growth, replacement of lost or damaged cells, and multiplication of somatic cells. However, the production of gametes from diploid cells is not a function of mitosis. Gametes, which are sperm and egg cells, are produced through a different process called meiosis, which involves two rounds of cell division to reduce the number of chromosomes in the resulting cells.
28.
A micrograph of a dividing cell from a mouse showed 19 chromosomes, each consisting of two sister chromatids. During which of the following stages of cell division could this picture have been taken?
Correct Answer
E. PropHase 2 of meiosis
Explanation
During prophase 2 of meiosis, the sister chromatids separate and move towards opposite poles of the cell. This results in the formation of haploid cells with half the number of chromosomes as the parent cell. Since the picture showed 19 chromosomes, each consisting of two sister chromatids, it suggests that the cell is undergoing meiosis and has not yet completed the second round of division. Therefore, the picture could have been taken during prophase 2 of meiosis.
29.
Cytochalisin B is a chemical that disrupts microfilaent formation. This chemical would interfere with
Correct Answer
C. Cleavage
Explanation
Cytochalisin B disrupts microfilament formation, which is essential for the process of cleavage. Cleavage is the division of a cell into two daughter cells during cell division. Microfilaments play a crucial role in the formation of the contractile ring, which constricts the cell membrane during cleavage. Therefore, if Cytochalisin B interferes with microfilament formation, it would hinder the process of cleavage.
30.
It is difficult to observe individual chromosomes during interphase because
Correct Answer
B. Hey are in the form of long thin strands
Explanation
During interphase, chromosomes are in the form of long thin strands called chromatin. This is because the DNA has not yet condensed and replicated to form distinct chromosomes. Therefore, it is difficult to observe individual chromosomes during this phase.
31.
A fruit fly somatic cell contains 8 chromosomes. This means that _ different combinations of chromosomes are possible in its gametes
.
Correct Answer
C. 16
Explanation
A fruit fly somatic cell contains 8 chromosomes. During meiosis, the chromosomes undergo recombination and independent assortment, resulting in different combinations of chromosomes in the gametes. Each chromosome can independently assort, so the total number of possible combinations is 2^8, which equals 256. However, since the question asks for the number of different combinations, we divide this number by 2 to account for the fact that each combination can be produced in two different ways (e.g., AB and BA). Therefore, the correct answer is 256/2 = 128.
32.
If a fragment of a chromosome breaks off and then reattaches to the original chromosome but in the reverse direction, the resulting chromosomal abnormality is called
.
Correct Answer
B. An inversion
Explanation
An inversion is a chromosomal abnormality that occurs when a fragment of a chromosome breaks off and reattaches to the original chromosome, but in the reverse direction. This results in a rearrangement of genetic material within the chromosome.
33.
Why are individuals with an extra chromosome 21, which causes down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?
a) there are probably more genes on chromosome 21 than on the others b) chromosome 21 is a sex chromosome and chromosomes 3 and 16 are not c) down syndrome is not more common, just more serious d) extra copies of the chromosomes are probably fatal e) nondisjunction of chroosoe 21 probably occurs more frequently
.
Correct Answer
D. Extra copies of the chromosomes are probably fatal
Explanation
The correct answer is that extra copies of the chromosomes are probably fatal. This means that individuals with an extra chromosome 3 or chromosome 16 are less likely to survive, resulting in fewer individuals with these extra chromosomes compared to individuals with an extra chromosome 21. This could be due to the fact that having extra copies of certain genes on chromosome 21 may be less detrimental to survival compared to having extra copies of genes on chromosomes 3 or 16.