Match the phase of meiosis with its correct description using the word bank provided. Compare the number and type of cells that result from meiosis vs. It involves two divisions called meiosis i and meiosis ii. At places where the maternal and paternal homologs cross called chiasmas, the chromotids may break and when repair enzymes put them back together, they may have exchanged some genetic material in the process known as crossing over. For different alleles, one will be expressed over the other segregation chromosomes separate during meiosis each gamete receives 1 copy of a gene independent assortment genes for different traits are assorted independently of each other during gamete formation. A gene is a biological unit of genetic information which is located in a definite position or locus on a filamentous or rodshaped chromosome contained in the nucleus. Meiosis reading guide new castle community school corp. This activity is perfect for clarifying the importance of crossing over in meiosis. Some lines will have more than one answer, and the stages can be used more than once or not at all. A cell has a diploid number of 60, what is the organisms haploid number. During tetrad formation, alleles can be exchanged between chromatids, a process called crossingover.
Students use colored paperclips to model the development of haploid cells. Molecular basis for mendels postulates unit factors in pairs a pair of genes controls a trait dominance recessiveness for different alleles, one will be expressed over the other segregation chromosomes separate during meiosis each gamete receives 1 copy of a gene independent assortment genes for different traits are assorted. Study 22 terms meiosis worksheet flashcards quizlet. It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase i of meiosis during a process called. A true b false crossing over occurs in a mitosis b meiosis i c meiosis il the sperm cell of a fox contains 30. Another difference is that after the first meiotic division, the cells do not reenter interphase and dna is not replicated. During meiosis, the two chromosomes in each homologous pair exchange segments, through a process called crossing over. Crossingover occurs during the stage of meiosis called. The first part in meiosis 1 is prophase where the chromosomes condense, pair up, and exchange bits of dna. The animation serves primarily as an aid to help students visualize the crossing over process so that they will be better equipped to complete the handson modeling activity that will follow. Jul 28, 2006 during meiosis, crossingoverthe exchange of genetic material between maternal and paternal chromosomesis stringently controlled to restrict the number of crossovers per chromosome pair.
Meiosis can be a difficult concept to understand because it is a reduction division that results in unique gametes due to crossingover that occurs in prophase i of meiosis. Recombination in metaphase 1 the pairs line up in the center of the cell where in the next step they will be pulled apart. In meiosis homologous chromosomes pair allows crossing over of genetic material, but homologous do not pair in mitosis. Chromosomal crossover, or crossing over, is the exchange of genetic material between two homologous chromosomes nonsister chromatids that results in recombinant chromosomes during sexual reproduction. Chromosomes carry genetic material in the form of strands of dna. Mitosis involves one division cycle and results in diploid daughter cells. From this narrated and animated powerpoint presentation, students will. Crossing over is important because it adds variation to the offspring and contributes to changes within a species. Some lines will have more than one answer, and the stages can be used more than once or. Mitosis and meiosis indiana university bloomington. In what phase do homologous chromosomes pair up and crossing over can occur.
What is crossing over and why is it important in meiosis. In simple terms, the crossing over definition equates to genetic recombination. Telophase ii nuclear membrane reforms, cytoplasm divides, 4 daughter cells formed 4. Each replicated chromosome pairs with its corresponding homologous chromosome forming a tetrad.
Join the amoeba sisters as they explore the meiosis stages with vocabulary including chromosomes, centromeres, centrioles, spindle fibers, and crossing over. Paired homologous chromosomes line up across the center of the cell. Students compare terms such as diploid and haploid, mitosis and meiosis, and germ cells and somatic cells. You now have a tetrad formed during prophase i of meiosis.
Students will also have an opportusnity to analyze mechanism involved with loss of cell cycle control in cancer. Meiosislesson overview gene mapping in 1911, columbia university student alfred sturtevant wondered if the frequency of crossingover between genes during meiosis might be a clue to the genes locations. In meiosis ii, the sister chromatids are pulled apart from each other to give rise to four haploid daughter cells. Meiosis is a specialized type of cell division which reduces the chromosome number by half. How do the genetic contents of cells resulting from mitosis and meiosis differ. In metaphase 1 of meiosis, bivalents orient at the metaphase plate and homologous are paired. Sturtevant reasoned that the farther apart two genes were on a chromosome, the more likely it would be that a crossover event would. It can be used as classwork, homework, or as a study guide. Biology 1 worksheet iii selected answers the function of meiosis is to produce haploid gametes from a diploid cell. Meiosis is a source of genetic variation due to crossing over when homologous. A true b false crossing over is the exchange of dna segments between sister chromatids. Anaphase i spindle fibers move homologous chromosomes to opposite sides 3. This worksheet is intended to reinforce concepts related to meiosis and sexual reproduction. Chapter 5 the cell cycle, mitosis, and meiosis worksheets.
This process occurs in all sexually reproducing eukaryotes both singlecelled and multicellular including animals, plants, and fungi. Homologous pairs of chromosomes are tangled together by a process called crossing over. This meiosis activity covers the following crossing over. Each replicated chromosome pairs with its corresponding homologous chromosome. Pdf meiosis and mitosis answers worksheet biology is fun meiosis and mitosis answers 1. Exchange of genetic material between nonsister chromatids during meiosis i at synapsis, a nucleoprotein lattice called the synaptonemal complex appears between homologues holds homologues together aligns dna of nonsister chromatids allows crossing over to occur then homologues separate and are distributed to different. How many cells are present at the end of meiosis i. Which of the following best describes how the process of crossing over during.
This activity focuses on crossing over and nondisjunction an optional part of the activity. Are the gametes spermegg produced by meiosis identical. Meiosis i will separate the chromosomes and meiosis ii will separate the chromatids, making 4 daughter cells. The function of meiosis is to produce haploid gametes from a diploid cell. Chiasma show where crossing over has occurred between.
Write a brief description of each phase dont forget crossing over. Meiosis is reduction division whereby the cell divides twice to reduce the chromosome number by half. Meiosis is a source of genetic variation due to crossing over when homologous chrom osomes exchange parts. During replication, dna segments can be swapped to form chromosomes with a new combination of genetic material. Meiosis and crossing over in sordaria is also examined in this experiment.
Many eggs from the same human woman will be genetically identical to each other. Model the appearance of the four gamete cells that will result at the end of meiosis. A detailed look at the completion of meiosis i, including metaphase i, anaphase i, telophase i, and cytokinesis. Crossing over independent assortment rearrangement of genes to produce genetic variation in gametes. Phases of meiosis on the lines provided, identify the stage of meiosis i or meiosis ii in which the event described occurs. You will receive your score and answers at the end. Crossing over creates a system which allows almost infinite variation. Which of the graphs below best depicts change in chromosome number through the cell cycle, beginning at g1 and ending after meiosis. A name of phase description prophase i homologous chromosomes pair up and form tetrad 2. Label all key structures homologues, sister chromatids, centromere, nuclear membrane, spindle fibers, nucleus.
Ninth grade lesson meiosis, part 2 modeling crossing over. This process of crossing over and the resulting recombination, exchange of gene alleles across the. Comparing mitosis and meiosis preposttest with answer key. Unlike mitosis, meiosis results in the formation of. A cell with a diploid number of 20 undergoes meiosis. Crossing over each chromatid may exchange a part of itself with its homolog as it crosses over the other during late prophase i or early metaphase i of meiosis homologous pairs matching chromosomes that each came from either the father or the mother. It is in the prophase of meiosis i that crossing over of the chromosomes takes place, and the homologous chromosomes are separated into two daughter cells. Comparing and contrasting describe a similarity and a difference between meiosis i and meiosis ii. Record the four gametes chromosomes and their genes in the data table.
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