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    why is meiosis important for organisms? it allows for genetic variation among organisms. it determines which genes are dominant and which are recessive. it produces genetically identical cells. it provides a means of asexual reproduction.

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    Meiosis assignment and quiz Flashcards

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    Meiosis assignment and quiz

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    Identify the phases of meiosis I described below.

    Homologous chromosomes are separated.

    Homologous chromosome are paired.

    Nuclear envelopes form around separated chromosomes.

    The centrosome replicates.

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    anaphase 1 prophase 1 telophase 1 metaphase 1

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    Identify the phases of Meiosis II described below.

    Chromosomes are lined up by spindle fibers.

    Nuclear envelope forms around each set of DNA.

    Sister chromatids are pulled apart.

    Centromeres move toward the poles of the cell.

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    metaphase II telophase II anaphase II prophase II

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    Campbell Biology (AP Edition)

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    Cain, Jackson, Minorsky, Reece, Urry, Wasserman

    715 explanations

    Fundamentals of Biochemistry: Life at the Molecular Level

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    Charlotte W. Pratt, Donald Voet, Judith G. Voet

    980 explanations

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    Terms in this set (19)

    Identify the phases of meiosis I described below.

    Homologous chromosomes are separated.

    Homologous chromosome are paired.

    Nuclear envelopes form around separated chromosomes.

    The centrosome replicates.

    anaphase 1 prophase 1 telophase 1 metaphase 1

    Identify the phases of Meiosis II described below.

    Chromosomes are lined up by spindle fibers.

    Nuclear envelope forms around each set of DNA.

    Sister chromatids are pulled apart.

    Centromeres move toward the poles of the cell.

    metaphase II telophase II anaphase II prophase II

    Explain the relationship between crossing over and genetic variation.

    What information did you include in your response?

    Crossing over is the process by which genetic material is exchanged by non-sister chromatids during meiosis.

    Crossing over results in a new combination of genetic information for the cell for a specific trait.

    Crossing over ensures that organisms are not identical from generation to generation.

    Genetic recombination allows for a variation in genetic material that is passed through the generations.

    Explain how independent assortment occurs in cells and explain its importance.

    What information did you include in your response?

    Independent Assortment is the second law of inheritance

    Traits are passed from parents to offspring independently of one another.

    Independent assortment is random and occurs during Metaphase I of meiosis.

    There are two possible alignments for the chromosomes.

    Since the alignments are random and not assigned, genetic variation occurs.

    Which discovery did Gregor Mendel make?

    Traits are inherited independently of each other.

    Traits are inherited as a tetrad.

    Traits are inherited as homologous pairs.

    Traits are inherited as a set, from one parent.

    Traits are inherited independently of each other.

    During which phase of meiosis does crossing over of chromosomes occur?

    prophase I metaphase I anaphase I telophase I prophase I

    How many chromosomes does a child inherit from his or her parents?

    23 from the mother and 23 from the father

    46 from the mother 46 from the father

    46 from the mother and 46 from the father

    23 from the mother and 23 from the father

    Why is meiosis important for organisms?

    It allows for genetic variation among organisms.

    It determines which genes are dominant and which are recessive.

    It produces genetically identical cells.

    It provides a means of asexual reproduction.

    It allows for genetic variation among organisms.

    Which consist of sperm cells and egg cells?

    gametes tetrads diploids chromosomes gametes

    Genetic variation occurs through genetic recombination.

    mc011-1.jpg (The one with the chromosomes in the cells)

    Which method of genetic recombination is illustrated in the diagram?

    independent assortment

    fertilization crossing over sexual reproduction

    independent assortment

    The diagram illustrates one method of genetic recombination.

    mc014-1.jpg (With just the pink and blue chromosomes)

    Which method of genetic recombination is illustrated in the diagram?

    crossing over

    independent assortment

    fertilization tetrad formation crossing over

    Which best illustrates how Gregor Mendel used creativity that lead to scientific discovery?

    He noticed that traits were passed on from parents to offspring.

    He chose a parent generation and carefully studied its traits.

    He used pea plants to study the patterns of heredity.

    He observed how specific traits were passed from parent to offspring.

    He used pea plants to study the patterns of heredity.

    Three cells undergo meiosis. How many haploid cells are produced?

    3 6 9 12 12

    Which definition correctly describes a haploid cell during meiosis?

    a cell that has double the number of chromosomes as the parent cell

    Source : quizlet.com

    7.1 Sexual Reproduction – Concepts of Biology – 1st Canadian Edition

    7.1 SEXUAL REPRODUCTION

    Learning Objectives

    By the end of this section, you will be able to:

    Explain that variation among offspring is a potential evolutionary advantage resulting from sexual reproduction

    Describe the three different life-cycle strategies among sexual multicellular organisms and their commonalities

    Understand why you could never create a gamete that would be identical to either of the gametes that made yo

    Sexual reproduction was an early evolutionary innovation after the appearance of eukaryotic cells. The fact that most eukaryotes reproduce sexually is evidence of its evolutionary success. In many animals, it is the only mode of reproduction. And yet, scientists recognize some real disadvantages to sexual reproduction. On the surface, offspring that are genetically identical to the parent may appear to be more advantageous. If the parent organism is successfully occupying a habitat, offspring with the same traits would be similarly successful. There is also the obvious benefit to an organism that can produce offspring by asexual budding, fragmentation, or asexual eggs. These methods of reproduction do not require another organism of the opposite sex. There is no need to expend energy finding or attracting a mate. That energy can be spent on producing more offspring. Indeed, some organisms that lead a solitary lifestyle have retained the ability to reproduce asexually. In addition, asexual populations only have female individuals, so every individual is capable of reproduction. In contrast, the males in sexual populations (half the population) are not producing offspring themselves. Because of this, an asexual population can grow twice as fast as a sexual population in theory. This means that in competition, the asexual population would have the advantage. All of these advantages to asexual reproduction, which are also disadvantages to sexual reproduction, should mean that the number of species with asexual reproduction should be more common.

    However, multicellular organisms that exclusively depend on asexual reproduction are exceedingly rare. Why is sexual reproduction so common? This is one of the important questions in biology and has been the focus of much research from the latter half of the twentieth century until now. A likely explanation is that the variation that sexual reproduction creates among offspring is very important to the survival and reproduction of those offspring. The only source of variation in asexual organisms is mutation. This is the ultimate source of variation in sexual organisms. In addition, those different mutations are continually reshuffled from one generation to the next when different parents combine their unique genomes, and the genes are mixed into different combinations by the process of meiosis. Meiosis is the division of the contents of the nucleus that divides the chromosomes among gametes. Variation is introduced during meiosis, as well as when the gametes combine in fertilization.

    The Red Queen Hypothesis

    There is no question that sexual reproduction provides evolutionary advantages to organisms that employ this mechanism to produce offspring. The problematic question is why, even in the face of fairly stable conditions, sexual reproduction persists when it is more difficult and produces fewer offspring for individual organisms? Variation is the outcome of sexual reproduction, but why are ongoing variations necessary? Enter the Red Queen hypothesis, first proposed by Leigh Van Valen in 1973.1 The concept was named in reference to the Red Queen’s race in Lewis Carroll’s book, Through the Looking-Glass, in which the Red Queen says one must run at full speed just to stay where one is.

    All species coevolve with other organisms. For example, predators coevolve with their prey, and parasites coevolve with their hosts. A remarkable example of coevolution between predators and their prey is the unique coadaptation of night flying bats and their moth prey. Bats find their prey by emitting high-pitched clicks, but moths have evolved simple ears to hear these clicks so they can avoid the bats. The moths have also adapted behaviors, such as flying away from the bat when they first hear it, or dropping suddenly to the ground when the bat is upon them. Bats have evolved “quiet” clicks in an attempt to evade the moth’s hearing. Some moths have evolved the ability to respond to the bats’ clicks with their own clicks as a strategy to confuse the bats echolocation abilities.

    Each tiny advantage gained by favorable variation gives a species an edge over close competitors, predators, parasites, or even prey. The only method that will allow a coevolving species to keep its own share of the resources is also to continually improve its ability to survive and produce offspring. As one species gains an advantage, other species must also develop an advantage or they will be outcompeted. No single species progresses too far ahead because genetic variation among progeny of sexual reproduction provides all species with a mechanism to produce adapted individuals. Species whose individuals cannot keep up become extinct. The Red Queen’s catchphrase was, “It takes all the running you can do to stay in the same place.” This is an apt description of coevolution between competing species.

    LIFE CYCLES OF SEXUALLY REPRODUCING ORGANISMS

    Fertilization and meiosis alternate in sexual life cycles. What happens between these two events depends on the organism. The process of meiosis reduces the resulting gamete’s chromosome number by half. Fertilization, the joining of two haploid gametes, restores the diploid condition. There are three main categories of life cycles in multicellular organisms: diploid-dominant, in which the multicellular diploid stage is the most obvious life stage (and there is no multicellular haploid stage), as with most animals including humans; haploid-dominant, in which the multicellular haploid stage is the most obvious life stage (and there is no multicellular diploid stage), as with all fungi and some algae; and alternation of generations, in which the two stages, haploid and diploid, are apparent to one degree or another depending on the group, as with plants and some algae.

    Source : opentextbc.ca

    Genetic Variation in Meiosis

    Study the basics of meiosis and fertilization and learn about the connection between meiosis and genetic variation. See how genetic variation in...

    Science Courses / Course / Chapter

    Genetic Variation in Meiosis and Fertilization

    Sujata Kumari, Elizabeth Friedl

    Study the basics of meiosis and fertilization and learn about the connection between meiosis and genetic variation. See how genetic variation in meiosis occurs. Updated: 01/12/2022

    Table of Contents

    Understanding Meiosis and Fertilization

    Genetic Variation in Meiosis

    Crossing Over Lesson Summary Create an account

    Understanding Meiosis and Fertilization

    The inheritance of traits from one generation to the next via the process of reproduction ensures continuity of life in all living forms on the planet. Passing genes that control certain traits through the generations is known as heredity. The transmission of genetic information occurs differently in lower or simpler organisms than that of complex ones via asexual and sexual reproduction, respectively.

    Unicellular organisms like bacteria or yeast reproduce via asexual reproduction, wherein genetic material is duplicated and one identical copy is passed onto the daughter cells via cytokinesis during the mitosis process. Asexual reproduction produces progenies, which are clones of their parent cells. Sexual reproduction, on the other hand, occurs in larger multicellular organisms like humans, plants, and animals. In sexual reproduction, genetic traits from two individuals (male and female) are passed onto their offspring creating a hybrid of the two parent organisms. In certain plants, flowers are bisexual, bearing both male (stamen) and female (ovary) reproductive organs. Sex cells, or gametes, from both the parents or reproductive organs participate and combine during sexual reproduction. Such offspring has genetic and physical traits from both parents (such as blue eyes from mother and dark skin from father), along with some newer traits not found in the parents. Sexual reproduction is accomplished by the production of sex cells or gametes through the process of meiosis and subsequent random fertilization of these gametes. Different modes of fertilization are seen in nature through internal fertilization, as in mammals, or external fertilization, as found in some frogs, fishes and flowering plants. Through the process of meiosis and random fertilization, sexual reproduction allows for the exchange and recombination of genetic material contributing to genetic variation in a population.

    Meiosis is a special kind of cell division occurring in the body with the purpose of making gametes, or sex cells. Unlike mitosis which occurs in all the other types of cells, meiosis only occurs in gamete-forming cells. The end products of meiotic cell division are cells with half the number of chromosomes contained in the parent cells. Thus, meiosis forms haploid cells (cells with only one set of chromosomes; denoted as n) when starting from a diploid parent cell (cells with two sets of chromosomes; denoted as 2n). In humans (diploid organisms), cells undergoing meiosis are diploid with 46 total chromosomes, or 23 pairs of chromosomes. After meiotic division, one diploid cell gives rise to four haploid cells. In humans, the haploid cells made in meiosis are sperm (in males) and eggs (in females).

    Sexual reproduction proceeds with the fertilization process wherein a sperm cell and an egg are combined to produce a zygote. In this process, two haploid gametes join and restore a complete diploid set of genomes in the zygote.

    How Does Meiosis Increase Genetic Variation?

    Genetic variation is defined as the differences in the genetic composition of organisms in a population. Genetic variation in a population is very crucial in order to adapt to an environment and develop better survival and reproduction. Thus, genetic variation acts as a driving force towards natural selection and evolution. A few examples of genetic variation include:

    Skin color, hair color, blood types, or the shape of eyes within a human population

    Modified leaves of carnivorous plants to trap prey

    Modifications in flowers to attract pollinators

    Camouflage and blending characteristics including animals mimicking leaves or sticks, and cheetah stripes that blend in with the surrounding environment

    Major causes for genetic variation include DNA heritable mutation, gene flow (also known as gene migration, or the introduction of new genes into a population via migration of organisms into a new environment), and sexual reproduction through the process of meiosis and random fertilization.

    Overview of the meiosis process during gamete formation in a diploid organism:

    Interphase Cell grows in size

    DNA is replicated

    Cell prepares for division

    Meiosis-I (Reductional Division)Prohase-I Chromosomes condense and pair up as homologous chromosomes

    Tetrad (composed of four chromatids) formation occurs

    Genetic recombination via crossing over

    Metaphase-I Tetrads align at the metaphase plate

    The centromeres of homologous chromosomes are oriented toward the opposite cell poles

    Anaphase-I Homologous chromosome pairs separate and move to opposite poles

    Either one of each pair goes to a respective pole

    Telophase-I and cytokinesis Each pole has a haploid number of chromosomes

    Nuclear membranes reform around them

    Source : study.com

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