Female animals produce eggs through the process of oogenesis. Similar to what takes place in spermatogenesis, primordial diploid cells divide mitotically to produce diploid oogonia that can divide repeatedly by mitosis, or enter meiosis. An oogonium that has entered prophase I is called a primary oocyte and is diploid. Upon completion of meiosis. I, the cell divides, but unequally. One of the newly produced haploid cells receives most of the cytoplasm and is called the secondary oocyte.
The other haploid cell receives only a small portion of the cytoplasm and is called the first polar body. Ultimately, the secondary oocyte will complete meiosis II and produce two haploid cells. One cell, the ovum, will receive most of the cytoplasm from the secondary oocyte. The smaller haploid cell is called the second polar body. Typically, the polar bodies disintegrate, and only the ovum is capable of being fertilized.
Outline the processes of male gamete formation and female gamete formation in plants. Solution: Plants alternate between a multicellular haploid stage called the gametophyte and a multicellular diploid stage called the sporophyte. Meiosis in the diploid sporophyte stage of plants produces haploid spores that develop into the gametophyte.
The gametophyte produces gametes by mitosis. In flowering plants, the microsporocytes found in the stamen of the flower undergo meiosis to produce four haploid microspores. Each microspore divides by mitosis to produce the pollen grain, or the microgametophyte. Within the pollen grain are two haploid nuclei. One of the haploid nuclei divides by mitosis to produce two sperm cells. The other haploid nucleus directs the formation of the pollen tube.
Female gamete production in flowering plants takes place within the megagametophyte. Megasporocytes found within the ovary of a flower divide by meiosis to produce four megaspores.
Three of the megaspores disintegrate, while the remaining megaspore divides mitotically to produce eight nuclei that form the embryo sac or female gametophyte. Of the eight nuclei, one will become the egg. What do the two socks of a pair represent in the cell cycle? Solution: The two chromatids of a chromosome b.
In the riddle, each blind man buys his own pairs of socks, but the clerk places all of the pairs into one bag. Thus, there are two pairs of socks of each color in the bag two black pairs, two blue pairs, two gray pairs, etc. What do the two pairs four socks in all of each color represent? Solution: The two chromosomes of a homologous pair.
In the cell cycle, what is the thread that connects the two socks of a pair? Solution: Cohesin d. In the cell cycle, what is the molecular knife that cuts the thread holding the two socks in a pair together? Solution: The enzyme separase e. What in the riddle performs the same function as spindle fibers?
Solution: The hands of the two blind men f. What would happen if one man failed to grasp his sock of a particular pair and how does it relate to events in the cell cycle? Solution: If one man failed to grasp his sock, it would be difficult for the knife to cut the string holding them together.
Similarly, if each chromatid is not attached to spindle fibers and pulled in opposite directions, the two chromatids will not separate and both would migrate to the same cell. This cell would have two copies of one chromosome.
Section 2. A cell has a circular chromosome and no nuclear membrane. Its DNA is complexed to some histone proteins. Does this cell belong to a eubacterium, archaea, or eukaryote? Explain your reasoning. Solution: This cell is most likely an archaea. The cell is not eukaryotic because it lacks a nuclear membrane and has a single circular chromosome. The cell is not a eubacterium because it has histone proteins, which are present in archaea and eukaryotes but lacking in eubacteria.
A certain species has three pairs of chromosomes: an acrocentric pair, a metacentric pair, and a submetacentric pair. Draw a cell of this species as it would appear in metaphase of mitosis. A biologist examines a series of cells and counts cells in interphase, 20 cells in prophase, six cells in prometaphase, two cells in metaphase, seven cells in anaphase, and five cells in telophase. If the complete cell cycle requires 24 hours, what is the average duration of the M phase in these cells?
Of metaphase? Solution: To determine the average duration of M phase in these cells, the proportion of cells in interphase, or in each stage of M phase, should be calculated by dividing the number of cells in each stage by the total number of cells counted. To calculate the time required for a given phase, multiply 24 hours by the proportion of cells at that stage.
This will give the average duration of each stage in hours. The average duration of M phase can be determined by adding up the hours spent in each stage of mitosis. In these cells, M phase lasts 4. The table shows that metaphase requires 0. A certain species has three pairs of chromosomes: one acrocentric pair and two metacentric pairs.
Draw a cell of this species as it would appear in the following stages of meiosis. Metaphase I Solution: b. Anaphase I Solution: c. Metaphase II Solution: d. Anaphase II Solution:. Construct a table similar to that in Figure 2.
A cell in G 1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stages?
Solution: The number of chromosomes and DNA molecules depends on the stage of the cell cycle. Each chromosome contains only one centromere, but after the completion of S phase, and prior to anaphase of mitosis or anaphase II of meiosis, each chromosome will consist of two DNA molecules.
Each chromosome now consists of two DNA molecules. So a cell in G 2 will contain 12 chromosomes and 24 DNA molecules. Metaphase I of meiosis Solution: Neither homologous chromosomes nor sister chromatids have separated by metaphase I of meiosis.
Therefore, the chromosome number is 12, and the number of DNA molecules is Anaphase I of meiosis Solution: During anaphase I of meiosis, homologous chromosomes separate and begin moving to opposite ends of the cell. However, sister chromatids will not separate until anaphase II of meiosis.
The number of chromosomes is still 12, and the number of DNA molecules is Anaphase II of meiosis Solution: Homologous chromosomes were separated and migrated to different daughter cells at the completion of meiosis I. However, in anaphase II of meiosis, sister chromatids separate, resulting in a temporary doubling of the chromosome number in the now haploid daughter cell.
The number of chromosomes and the number of DNA molecules present will both be The haploid cells will contain six chromosomes and 12 DNA molecules. After cytokinesis following mitosis Solution: After cytokinesis following mitosis the daughter cells will enter G 1. Each cell will contain 12 chromosomes and 12 DNA molecules.
How are the events that take place in spermatogenesis and oogenesis similar? How are they different? Solution: Both spermatogenesis and oogenesis begin similarly in that the diploid primordial cells spermatogonia and oogonia can undergo multiple rounds of mitosis to produce more primordial cells, or both types of cells can enter into meiotic division.
In spermatogenesis, cytokinesis is equal, resulting in haploid cells of similar sizes. Upon completion of meiosis II, four haploid spermatids have been produced for each spermatogonium that began meiosis.
In oogenesis, cytokinesis is unequal. At the completion of meiosis I in oogenesis, a secondary oocyte is produced, which is much larger and contains more cytoplasm than the other haploid cell produced, called the first polar body. At the completion of meiosis II, the secondary oocyte divides, producing the ovum and the second polar body.
Again, the division of the cytoplasm in cytokinesis is unequal, with the ovum receiving most of the cytoplasmic material. Usually, the polar bodies disintegrate, leaving the ovum as the only product of meiosis. All of the following cells, shown in various stages of mitosis and meiosis, come from the same rare species of plant.
Solution: To determine the diploid chromosome number in this plant, the number of centromeres present within a cell that contains homologous pairs of chromosomes must be determined. Remember, each chromosome possesses a single centromere. The location and presence of a centromere are determined by the attachment of the spindle fibers to the chromosome, which occurs at the centromere in the above diagram.
Only the cell in stage a clearly has homologous pairs of chromosomes. So the diploid chromosome number for cells of this species of plant is six. Give the names of each stage of mitosis or meiosis shown. Solution: Cell 1 is undergoing anaphase of meiosis I, as indicated by the separation of the homologous pairs of chromosomes. Cell 2 in the diagram contains six chromosomes, the diploid chromosome number for this species.
Also in this cell, sister chromatids have separated, resulting in a doubling of the chromosome number within the cell from six to Based on the number of chromosomes, the separation of sister chromatids in this cell must be occurring during anaphase of mitosis. In cell 3 again, sister chromatids are being separated, but the number of chromosomes present in the cell is only six.
This indicates that no homologs are present within the cell, so in this cell the separation of sister chromatids is occurring in anaphase II of meiosis. Give the number of chromosomes and number of DNA molecules per cell present at each stage.
Solution: Cell 1, which is in anaphase I of meiosis contains six chromosomes and 12 DNA molecules or sister chromatids. Cell 2 has 12 chromosomes and 12 DNA molecules in anaphase of mitosis.
The amount of DNA per cell of a particular species is measured in cells found at various stages of meiosis, and the following amounts are obtained: Amount of DNA per cell 3.
Search Ebook here:. Pierce Publisher: W. Book Preface The new seventh edition continues this mission by expanding upon the powerful pedagogy and tools that have made this title so successful.
Designed by readallbooks. Download here Download Now here. Each chapter ends with an extensive bibliography so that the students and researchers may find it relevant to consult more literature on the subject than a book of this size can offer. The book is intended to fulfill the needs of undergraduate and post graduate students of botany, zoology and agriculture besides, teachers and researchers engaged in the field of genetics, cytogenetics, and molecular genetics. In general the readers will find each chapter of the book informative and easy to understand.
This introductory text assumes little prior scientific knowledge on the part of the student. It includes sufficient information for some shorter introductory botany courses open to both majors and nonmajors, and is arranged so that certain sections can be omitted without disrupting the overall continuity of the course.
Stern emphasizes current interests while presenting basic botanical principles. The first book devoted exclusively to the principles and practice of genetic counseling—now in a new edition First published in , A Guide to Genetic Counseling quickly became a bestselling and widely recognized text, used nationally and internationally in genetic counseling training programs.
Now in its eagerly anticipated Second Edition, it provides a thoroughly revised and comprehensive overview of genetic counseling, focusing on the components, theoretical framework, and unique approach to patient care that are the basis of this profession. The book defines the core competencies and covers the genetic counseling process from case initiation to completion—in addition to addressing global professional issues—with an emphasis on describing fundamental principles and practices.
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A fascinating text that addresses the clinical and educational challenges of treating psychiatric patients from a truly multidisciplinary perspective using a case-based format, Approach to the Psychiatric Patient: Case-Based Essays is the only book of its kind and an indispensable addition to the mental health practitioner's library.
The new edition builds upon the strengths that distinguished the first, with composite cases that are carefully constructed to capture real-world problems, followed by essays that provide clear and cogent perspectives on the case. These essays cover a wide range, from the more conventional such as differential diagnosis of anxiety or the clinical characteristics of delirium to the unusual and intriguing such as creativity and mental illness or an analysis of the case in relation to the classic, Strange Case of Dr.
Jekyll and Mr. Every chapter has been revised, and the book boasts many new co-contributors, as well as the addition of completely new essays. For example, in the chapter on geriatric depression, several new essays have been added on the topics of collaborative care and the embedded psychiatrist, depression and medical illness, and biomarkers to identify depression subtypes, while the chapter on terminal illness features new essays on spirituality and meaning-centered therapy.
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The Handbook of the Biology of Aging, Sixth Edition, provides a comprehensive overview of the latest research findings in the biology of aging. Intended as a summary for researchers, it is also adopted as a high level textbook for graduate and upper level undergraduate courses. Though a selected few topics are similar to the Fifth Edition, these chapters are authored by new contributors with new information.
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