Meiosis Unit Student Design Cover Page (see guidelines on page 10) 40 | P a g e Meiosis Unit Front Page At the end of this unit, I will: Know the difference between sexual and asexual reproduction. Understand the difference between haploid and diploid cells. Understand the steps involved in meiosis with regard to gametes and chromosome number. Interpret a karyotype, being able to identify gender or potential disorder from the karyotype. Roots, Prefixes and Suffixes I will be able to understand when I see them in words are: Homo-, chromo-, hap-, di-, karyo-logous, -some The terms I can completely define are: Gene, homologous chromosome, gamete, haploid, fertilization, diploid, meiosis, crossing over Karyotype, telomere, nondisjunction The assignments I will have completed by the end of this unit are: Meiosis Unit Cover Page Meiosis unit notes Completed the “Using Karyotypes to Predict Genetic Disorders” web activity Completed the “Patient Histories” web activity Acted out Meiosis using pipe cleaners as chromosomes Memorized and sung the Meiosis Square Dance for Extra Credit Completed the Meiosis Review Worksheet Meiosis Unit Backpage 41 | P a g e Meiosis and Reproduction Notes Warm-up: Humans have 46 chromosomes in all of their body cells. The first cell of the organism is made by joining egg and sperm. 1. How many chromosomes in a human egg or sperm cell? Explain. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. Can cell division by mitosis (duplication of cells) produce egg or sperm? Explain. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 42 | P a g e Meiosis and Sexual Reproduction: Asexual Reproduction What is Asexual Reproduction? Called _________________ reproduction in plants • A form of duplication using only ____________. – Example: _________________________ _________________________________ What are the limitations of asexual reproduction? Produces only genetically ___________________ offspring since all divisions are by mitosis. • Offspring called meaning that each is an exact copy of the original organism • This method of reproduction is __________ and effective allowing the spread of an organism – • Example: _________________________ Since the offspring are identical, there is no mechanism for introducing • What are some specific examples of asexual reproduction? ______ . In prokaryotes and some one-celled eukaryotes, cells undergo ____________ _____________ • Hydra reproduce by _______________ • Planaria reproduce by ____________________ • Several plants reproduce through _______________ reproduction. – Most of these organisms can reproduce _______________ as well. 43 | P a g e Understanding haploid and diploid If N=2, 2N would look like: = A chromosome = A chromosome There are 2 different types of chromosomes in this cell. 2N means that this cell is diploid (or there are two copies of each chromosome). How many total chromosomes are present in this cell? _____ 1. Draw the chromosomes in a diploid cell of an organism where N=3. 2. How many combinations of haploid (eggs or sperm) cells are possible if N=2? Draw the possible combinations. 3. How many combinations of haploid cells are possible if N=3? Draw the possible combinations. 44 | P a g e Sexual Reproduction Why do organisms have sex? Sexual reproduction increases ______________ by producing new ______________ combinations. What does sexual reproduction consist of? 1. ______________: Formation of two haploid sex cells (or _______________). • Meiosis is a process to convert a ________ cell to a ________ gamete, and cause a change in the genetic information to increase diversity in the offspring. • In humans, meiosis only occurs in the ___________ – Spermatogenesis: In the ___________ (in males) – Oogenesis: In the _________________ (in females) 2. Fertilization: Combination of genetic information from two separate cells that have one ________ the original genetic information. Where do gametes come from? • ______________ for fertilization usually come from separate parents • o Female produces an ___________ o Male produces _____________ Both gametes are haploid (1__), with a single set of ____________________ . What are is the ploidy levels of gametes? • The new individual is called a _____________, with two sets of chromosomes (____________ or 2___). • Once the zygote begins to divide, it is called an _________________. What is the name for the process in which two gametes combine? _________________________ 45 | P a g e What is the name for the way these chromosomes are organized? ___________________ Circle the sex chromosomes. What is the gender of this person? ____________________ 46 | P a g e Chromosomes and Karyotypes How many chromosomes do humans have? Humans have ______ chromosomes. What are some characteristics of chromosomes? • There is a __________ set for humans; __n = 46 • There are two types: 1. ______________ (#1 – 22) 2. _______ Chromosomes (#____) What are some characteristics of autosomes? • ______________ chromosomes • Humans have _____ sets of 2. o What are some characteristics of sex chromosomes? What can Chromosomes tell us? One from each parent • Humans have 1 set of ____. • Female sex chromosomes are ___________________ (X__) • Male sex chromosomes are _____________________(X__) Scientists can organize chromosomes in a cell into a ________________. In a karyotype, chromosomes are arranged in order of: 1. _____________ 2. _____________ _________________ 3. ___________________ ______________ 47 | P a g e Meiosis is often called / Meiosis can be broken up into two phases: and . Meiosis I: Prophase I is much like the prophase of mitosis: 1. ______________________________________________ 2. ___________________________________________ ____________________________________________ 3. ___________________________________________ _____________________________________________ However, unlike mitosis, where the chromosomes of a homologous pair are randomly scattered within the nucleus, in meiosis, 1. ________________________________________ _______________________________________________________ 2. ___________________________________________________________________________ _____________________________________________________________________________ 48 | P a g e Metaphase I Anaphase I Telophase I Metaphase I: align at the metaphase plate. Microtubules are attached to the . Anaphase I: Homologous pairs separate with together. remaining Telophase I: Two daughter cells are formed with each daughter containing only one of the homologous pair. Each daughter cell is now . Meiosis II: formation Prophase II: does not replicate, this is just like mitotic prophase. Metaphase II: Chromosomes align at the Anaphase II: pole. Telophase II: Cell division is complete. obtained. divide and sister chromatids migrate separately to each daughter cells are 49 | P a g e USING KARYOTYPES TO PREDICT GENETIC DISORDERS Use the following website to help you fill in the blanks and answer the following questions. http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/ 1. A normal human karyotype has ______ chromosomes: _____ pairs of autosomes and ____ sex chromosomes. Cells don’t always end up with these chromosomal numbers, though. The following text outlines what happens when cells end up with too much or too little genetic information. 2. Too many or too few chromosomes a. To understand how our cells might end up with too many or too few chromosomes, we need to know how the cells normally get _____ chromosomes. b. First we need to understand meiosis. Meiosis is the cell division process that produces egg and sperm cells (___________), which normally have ______ chromosomes each. c. If eggs and sperm only have one set of _____________________, then how do we end up with 46 chromosomes? During ______________________, when the egg and sperm fuse, the resulting _________________ has two copies of each chromosome needed for proper development, for a total of ________. 3. How can cells end up with too many or too few chromosomes? a. Sometimes chromosomes are incorrectly distributed into the egg or sperm cells during _______________. When this happens, one cell may get __________ copies of a particular chromosome, while another cell gets none. b. What happens if a sperm or egg cell with an abnormal number of chromosomes participates in fertilization? It depends on how many chromosomes the gamete has. For example, if a ___________ with an extra chromosome fertilizes an egg with a normal chromosome number, the resulting zygote will have _____ copies of one chromosome. This is called _______________. c. If a sperm that is missing a ___________________ fertilizes an egg, then the resulting zygote will have only one copy of that chromosome. This is called ________________________ d. People who are born with an abnormal number of chromosomes often have genetic disorders because their cells contain too much or too little genetic information. Scientists can predict genetic disorders by looking for extra or missing chromosomes in a ___________________. 50 | P a g e 4. Missing pieces of chromosomes a. In some cases, genetic material is missing from a chromosome. Such chromosomes are said to have __________________. b. Deletions large enough to be seen in a karyotype result in the loss of many _____________. In humans, these are less comman than deletions that remove small portions of a chromosome. c. A _________________________ is a chromosome rearrangement in which part of a chromosome breaks off and then reattaches to a different chromosome. QUIZ: Use the options listed below and your knowledge to answer the following questions. Some options will be used more than once. Normal female Turner Syndrome Normal male Klinefelter Syndrome Down Syndrome 1. _______________________ 5. _______________________ 2. _______________________ 6. _______________________ 3. _______________________ 7. _______________________ 4. _______________________ 8. _______________________ 51 | P a g e Patient Histories: Karyotyping Activity Introduction This exercise is a simulation of human karyotyping using digital images of chromosomes from actual human genetic studies. You will be arranging chromosomes into a completed karyotype, and interpreting your findings just as if you were working in a genetic analysis program at a hospital or clinic. Karyotype analyses are performed over 400,000 times per year in the U.S. and Canada. Imagine that you were performing these analyses for real people, and that your conclusions would drastically affect their lives. G Banding During mitosis, the 23 pairs of human chromosomes condense and are visible with a light microscope. A karyotype analysis usually involves blocking cells in mitosis and staining the condensed chromosomes with Giemsa dye. The dye stains regions of chromosomes that are rich in the base pairs Adenine (A) and Thymine (T) producing a dark band. A common misconception is that bands represent single genes, but in fact the thinnest bands contain over a million base pairs and potentially hundreds of genes. For example, the size of one small band is about equal to the entire genetic information for one bacterium. The analysis involves comparing chromosomes for their length, the placement of centromeres (areas where the two chromatids are joined), and the location and sizes of G-bands. 52 | P a g e Your assignment This exercise is designed as an introduction to genetic studies on humans. Karyotyping is one of many techniques that allow us to look for several thousand possible genetic diseases in humans. You will evaluate 3 patients' case histories, complete their karyotypes, and diagnose any missing or extra chromosomes. The assignment will be completed online, while the questions must be answered on the following page. Use the following website to help these patients diagnose their disorders from karyotypes and answer the following questions. http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping2.html Patient Histories Patient A Patient A is the nearly-full-term fetus of a forty year old female. Chromosomes were obtained from fetal epithelial cells acquired through amniocentesis. Complete Patient A's Karyotype (this will have to be done online). Patient B Patient B is a 28 year old male who is trying to identify a cause for his infertility. Chromosomes were obtained from nucleated cells in the patient's blood. Complete Patient B's Karyotype. Patient C Patient C died shortly after birth, with a multitude of anomalies, including polydactyly (more than five fingers on a hand) and a cleft lip. Chromosomes were obtained from a tissue sample. Complete Patient C's Karyotype. 53 | P a g e Making a diagnosis The next step is to either diagnose or rule out a chromosomal abnormality. In a patient with a normal number of chromosomes, each pair will have only two chromosomes. Having an extra or missing chromosome usually renders a fetus inviable (meaning that it will not live). In cases where the fetus makes it to term, there are unique clinical features depending on which chromosome is affected. Listed below are some syndromes caused by an abnormal number of chromosomes. Diagnosis Chromosomal Abnormality Normal # of chromosomes patient's problems are due to something other than an abnormal number of chromosomes. Klinefelter's Syndrome one or more extra sex chromosomes (i.e., XXY) Down's Syndrome Trisomy 21, extra chromosome 21 Trisomy 13 Syndrome extra chromosome 13 1. What observations can you make regarding patient A’s karyotype? _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 2. What diagnosis would you give patient A? Explain your answer. _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 3. What observations can you make regarding patient B’s karyotype? _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 54 | P a g e 4. What diagnosis would you give patient B? Explain your answer. _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 5. What observations can you make regarding patient C’s karyotype? _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 6. What diagnosis would you give patient C? Explain your answer. _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 55 | P a g e Meiosis Pipe Cleaner Play Introduction: A fruit fly’s testes are going through meiosis. What combination of alleles will be passed on in each of his gametes? Act 1: Scene 1 - Interphase a. The fruit fly has 6 chromosomes. The genotype of your fruit fly is GgBbrr. Remove these chromosomes from your bag to start the play. -Chromosome 1: with allele G (for Gray eyes) -Chromosome 2: with allele g (for green eyes) -Chromosome 3: with allele B (for black, solid body) -Chromosome 4: with allele b (for striped body) -Chromosome 5: with allele r (for shriveled wings) -Chromosome 6: with allele r (for shriveled wings) b. c. During S-phase of interphase, DNA duplication. (Exact size, color, and alleles, connecting at the centromere) Draw the arrangement of your chromosomes at this phase. Make sure to mark the alleles. Act 1: Scene 2 - Prophase I a. Homologous chromosomes pair up (not line up) b. Cross-over occurs on at least 2 homologous pair with at least 2 alleles. (Switch beads) c. Draw the new genetic combinations of your chromosomes at this phase after crossover. 56 | P a g e Act 1: Scene 3- Metaphase I a. Random line-up of homologous pairs. Act 1: Scene 4 – Anaphase I ,Telophase I, and Cytokinesis a. Homologous pairs separate b. Nuclei reform in two separate cells. c. Draw the chromosomes and alleles that exist in each of the two cells. Act 2: Scene 1 and 2 – Prophase II and Metaphase II a. Nuclei disappear b. Chromosomes line up at equator. Act 2: Scene 3 and 4 – Anapahse II ,Telophase II, and Cytokinesis a. Sister chromatids split to opposite poles b. Nuclei reform in 4 separate cells (4 haploid gametes are created) c. Draw the allele combination present in each of the haploid gametes. Act 3: Fertilization Your fly meets a female fly, and they like each other and want to have baby flies. Choose one of your four gametes to be the “sperm” Draw what kind of fly would be created if your fly’s sperm fertilized an egg in the other fly with the allele combination Gbr. Encore! Return all pipe-cleaners into the original bag! 57 | P a g e Act 1: Scene I – Interphase Act 1: Scene 2 – Prophase I Act 1: Scene 4 –After Cytokinesis of Meiosis I Act 2: Scenes 3 and 4 – After Cytokinesis of Meiosis II 58 | P a g e Fertilization Choose one of the four gametes created and write down its Genotype here __________. Have it fertilize another gamete with the genotype Gbr. What is the new offsprings full genotype? _________________ Draw the new fly offspring in the space below. Use color and make sure it matches the genotype. 59 | P a g e Meiosis Square Dance Lyrics Now coil up, coil up, coil up tight With a fiber stuck to your centromere If were to do meiosis right You’re pulled into the center here Interphase one is almost done On the central plate for metaphase two Marks the start of prophase one Just like before it’s déjà vu Face your partners and do them bow At Interphase one you duplicate Do-se-do crossover now So now that you can separate Allemande left with your left hand The fibers tugging this is it Promenade around the land Time for your chromatids to split Now grab your partner’s chromatid Anaphase, anaphase, anaphase two Crossing arms you’ll be glad you did This time you wave goodbye to you The nuclear membrane breaks down here At telophase two half the teams on hand Attach your fiber to you centromere You’re feeling sad you’re a single strand The fibers pull the dance is done Now this is just your normal state Hold on tight its metaphase one With some luck you’ll procreate Couples move to the central plate So rest a while and unwind too It’s anaphase one so you separate As the nuclear membrane surrounds you Now wave goodbye to reach your goal Now meiosis is complete Each partner move to the other pole Four nuclei from ones the treat Telophase one is mighty sad The cytoplasm will divide You’re all alone lost what you had Four gametes form with you inside Together we’ll no longer be And if we zoom out you will find These parts of you will be dear to me Many more of the same kind Prophase, prophase, prophase two And if you’re wondering what’s the use The spindles coming after you It’s all so we can reproduce… reproduce 60 | P a g e Meiosis Review 1. What terms are used to describe cells containing the normal number of chromosomes? ________________________________________ 2. What terms are used to describe cells containing half the number of chromosomes? ________________________________________ 3. Mitosis produces (circle one) diploid / haploid cells. 4. Meiosis produces (circle one) diploid / haploid cells. 5. How many pairs of chromosomes do human body cells have? _______ pairs. Chromosome Numbers of Some Common Organisms Organism Body cell (2n) Gamete (n) Human 46 _______ Garden Pea _______ 7 Fruit Fly 8 _______ Tomato _______ 12 Dog 78 _______ Chimpanzee _______ 24 Leopard Frog 26 _______ Corn _______ 10 Apple _______ 17 Indian Fern 1260 _______ 61 | P a g e Meiosis I (Prophase I, Metaphase I, Anaphase I, Telophase I) During prophase I, the _______________________ coil up and the _____________ fibers form. Then each pair of homologous chromosomes come together to form a four-part structure called a ____________ (tetra = what number?____). A tetrad consists of two homologous chromosomes, each made up of two sister chromatids. These 4 chromatids in a ____________ are held very close and tightly together. In fact, they are so close that the arms of non-sister chromatids can wind and twist around each other, and exchange genetic information (genes, DNA). This is called _______________ ____________. Crossing over results in new combinations of alleles. The Phases of MEIOSIS Before meiosis begins: Interphase Before meiosis begins, what must happen to the cell’s DNA/chromosomes? _____________________________________________ Meiosis occurs in sexual reproduction when 1 diploid germ cell produces 4 haploid cells that can mature to become ____________________ (sperm or ova). Prophase I Like prophase of mitosis: 1. The ______________ ______________ disappears. 2. ___________________ move to the opposite poles and the _______________ ___________ form between the centrioles. 3. __________________ condenses into sister _________________. Unlike prophase of mitosis: 1. Pairs of homologous chromosomes form _________. 2. _________________ _________ may occur. 62 | P a g e Metaphase I 1. Spindle fibers attach to _________________. 2. Tetrads line up at the ___________________ plate. Anaphase I 1. Tetrads, which consist of two ___________________ ________________, separate. Telophase I / Cytokinesis I 1. _______________ __________________ reappears. 2. _______________ ______________ disappears. 3. ___________________, the division of the cytoplasm and the organelles begins and ends forming two cells. Meiosis II (Prophase II, Metaphase II, Anaphase II, Telophase II) The purpose of meiosis II is to separate _______________ ___________________ of each chromosome into separate cells. 63 | P a g e Prophase II 1. _______________ _______________ disappears. 2. _______________ _____________ form. 3. __________________ condenses into sister _________________. Metaphase II 1. Sister chromatids attach to the ________________ ________________. 2. Sister chromatids line up at the ________________. Anaphase II 1. Sister chromatids separate into _____________________. 2. Chromosomes move to the opposite ___________. Telophase II 1. ______________ _________________ reforms. 2. 4 ______________ are formed. Quick Review 64 | P a g e Meiosis Unit Student Concept Map (see guidelines on page 10) 65 | P a g e Meiosis Unit Back Page The California State Standards I have come to use and understand are: (Please check all that you do feel you used and understood this unit) Meiosis is an early step in sexual reproduction in which the pairs of chromosomes separate and segregate randomly during cell division to produce gametes containing one chromosome of each type. Only certain cells in a multicellular organism undergo meiosis. New combinations of alleles may be generated in a zygote through the fusion of male and female gametes. Why approximately half of an individual’s DNA sequence comes from each parent. The role of chromosomes in determining an individual’s sex. The genetic basis for Mendel’s laws of segregation and independent assortment. 66 | P a g e