Iowa State University



Exam 4 Study Questions CELL DIVISION!!! Exam 3 Worksheet 1 Where do new cells come from?Preexisting cells (part cell theory)The two types of cell division are __Meiosis__ and __Mitosis__.Meiosis produces __gametes (eggs and sperm)__.Mitosis produces somatic cells. What are these? …all of the other cells in the body that are not reproductive cells Mitosis and Meiosis are both accompanied by __Cytokinesis__, which is what? …The division of the cytoplasm How many daughter cells does Meiosis form? How about Mitosis? Are the daughter cells identical or nonidentical?Meiosis produced 4 daughter cells that have half the amount of material as the parent cell, so they are NOT identical Mitosis produces 2 daughter cells because the genetic material is copied and divided equally between the two. Therefore, daughter cells are genetically IDENTICAL to the parent cellWhat are the three key events that mitosis and cytokinesis are responsible for in multicellular eukaryotes?Growth Wound repair Asexual reproduction How many types of chromosomes are in the human genome? Do all species have this same number of chromosomes?23…but we are diploid (2n, 2 copies of each) so 46 No, every speices has a different amount of chromosomes Draw a chromatid and label each part. *chromatids from the same chromosome are referred to as sister chromatids What happens in the M phase of the cell cycle?Mitotic phase; cell divides here Does division happen in Interphase?NOWhen in replication occurring?The S phase (synthesis phase) which is part of interphase What are the two gap phases? G1: first gap phase; occurs before S phase G2: second gap; occurs between S phase and mitosis Now put all of those steps in order, starting with the fist gap phase. G1 S phase G2 Mitosis Which lasts longer, interphase or m phase?InterphaseWhat has happened in the picture below?the chromosomes just went through S phase and have been replicated! What has happened in the picture below and what phase are we in?the chromosomes have condensed; this is the start of Mitosis (m phase)Complete the chart by saying what happens in each phase of Mitosis.Prophase PrometaphaseMetaphase Anaphase Telophase -Chromosomes condense and become visible in the light microscope.-spindle apparatus begins to form -start to see a breakdown of the nuclear envelope-formation of the mitotic spindle is complete -chromosomes line up in the middle on metaphase plate -centromeres split -sister chromatids are pulled by the spindle fibers toward opposite poles. Now that they’ve split they are individual unreplicated chromosomes.-as soon as they are no longer attached at the centromere, sister chromatids become daughter chromosomes -new nuclear envelope begins to form around each set of chromosomes -the mitotic spindle disintegrates-the chromosomes begin to decondense -mitosis is over when two independent nuclei have formed Cytokinesis occurs immediately after mitosis. What happens here?The cytoplasm divides to form daughter cellsEach daughter cell has its own nucleus and complete set of organelles A human cell (n=46) has __92__ chromatids and __46__ chromosomes during metaphase of Mitosis. Why is this?There will always be 46 chromosomes in a cell in the human genome. So when one of these is being replicated, that number will double. How do kinetochore microtubules shorten to pull daughter chromosomes apart during anaphase?The kinetochore microtubules shorten at the kinetochore to pull daughter chromosomes apart during anaphase SO microtubules break down at kinetochore and are pulling daughter chromosomes to sides of cell At cytokinesis, what type of organism has a cell plate?Plant At cytokinesis, what type of organism has a cleavage furrow?Animals, fungi and slime molds *end at Control of the Cell Cycle CELL DIVISION DAY 2!!! KEY Exam 3 Worksheet 2 Objective Questions and Answers What types of cells do mitosis and meiosis produce and how do these differ in terms of their chromosomes?Meiosis – produces gametes, 4 chromosomes that are not genetically identical the the parent, haploidMitosis – produces somatic cells, 2 chromosomes that are genetically identical to the parent, diploidWhat are the two main phases of the cell cycle? What are their subphases?Interphase includes G1, S phase and G2M phase includes Prophase, prometaphase, metaphase, anaphase and telophaseWhat is the purpose of the Gap phases of interphase?They are checkpoints that make sure the cell is ready to move on the next phase. How do chromosomes differ between the G1 and G2 phases?G1 = unreplicated G2 = replicated When do chromosomes condense during M phase? Prophase of Mitosis; right at the beginning What are the two types of microtubules and how do they differ functionally?Kinetochore microtubules – pulling chromosomes toward opposite poles Polar microtubules – pushing on poles to pull ends apart During what M-phase subphase do chromosomes line up along a central plane in the cell?MetaphaseDuring what subphase do sister chromatids divide?Anaphase How can the cell cycle differ across cell types?The speedFor example, brain cells last a very long timeCells in digestive tract do not How do chromosomes migrate toward the cell poles during anaphase?Disassembled at kinetochore and chromosomes are being pushed during disassembly towards the poles so the cell is ready to divideDuring cytokinesis, describe how plants and animals divide their cytoplasm. Plants – vesicles line up Animals – actin and myosin filaments pinch until there is two daughter cells What are the components of MPF and how do they differ?Mitosis Promoting Factor…2 components are cylin and kinase. Cylin is regulating when the cell division occurs (telling kinase what to do) and kinase actually carrying out phosphorylation (which means the addition of a phosphate group)When is concentration of the Cyclin component of MPF the highest and what triggers MPF’s activation for mitosis?Two phosphates will join, then one is removed, and that’s what activates the MPF and then the cell begins MitosisWhen does MPF degrade?Happens in Anaphase The enzymes are targeting the cyclin Kinase stays same concentration throughout cell cycle When do the checkpoints for the cell cycle occur and what is their purpose?In interphase:G1G2In M phase: Two in M phase If they don’t pass these checkpoints, they are marked for Apoptosis using p53What is the function of p53?Signal saying cell needs to be degraded because it’s having problems.If it’s not degraded, it will cause cancer. What is cancer caused by?Cells that grow in an uncontrolled fashionInvade nearby tissuesSpread to other sites on the body What is the difference between a benign tumor and a malignant tumor?Benign tumors are noninvasive and noncancerous. Malignant tumors are invasive, cancerous, can spread throughout body via the blood or lymph, initiate secondary tumorsWhen malignant tumors detach from the original tumor and invade other tissues, it is called what?Metastasis Chapter 13 – Meiosis…What is formed through the process of fertilization? Zygotes What is a karyotype? Give an example. An organisms characteristic number and type of chromosomes if referred to as its karyotype Ex: humans have 46 chromosomes; 1 pair sex chromosomes and 22 pairs autosomesWe have __23__ pairs of homologous chromosomes. Different versions of the same gene are called __alleles__. Give an example of this. Eye color – blue, green, brown, etc. Gene that controls eye color, on certain chromosome, 2 different alleles. One causes blue eyes and one causes green eyesSince 46 in the diploid number of chromosomes in humans, what would be the haploid number? 23 What is it that holds sister chromatids together?Centromere Describe the relationship between the red chromosome the blue chromosome. Non-sister chromatids Meiosis is known as reduction division. When is the reduction division within the cell actually occurring and what does this mean?Meiosis I, going from diploid to haploid What is separating in Meiosis II? Sister chromatids which will go to different daughter cells How do you go from a haploid state in the gametes to a diploid state in the zygotes?One from mom, one from dad, fertilization forms the zygote Meiosis in an adult produces haploid gametes that combine during fertilization to form a diploid zygoteIn mitosis, what was separating? How about Meisosis I? Chromosomes (sister chromatids) in MitosisHomologs in Meiosis I Sister chromatids in Meiosis II Based on the image below of replicated chromosomes removed from a wild maize cell at the metaphase stage of meiosis I, what is the haploid number (n) of maize?10 because we are still diploid in metaphase of Meiosis I, so we divide by 2. Remember that the diploid homologs have not yet separated. What is the major difference between meiosis II and mitosis in a diploid animal? Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cellsCrossover takes place in meiosis II (takes place in Meiosis I during homologue separation)Homologues align on the metaphase plate in meiosis II Sister chromatids separate in mitosis, and homologues separate in meiosis II Complete the chart by describing what happens in each phase of Meiosis I.Early prophase ILate prophase IMetaphase IAnaphase ITelophase I -chromosomes condense-spindle apparatus forms-nuclear envelope breaks down -homolog pairs come together in a pairing process called synapsis-non-sister chromatids begin to separate- chiasmata are formed so crossing over occurs btwn non-sister chromatids -line up at metaphase plate-paired HOMOLOGS separate -start to migrate to opposite poles-finish migrating to opposite poles-nuclear envelope forms **Cytokinesis takes places after this to divide the cell into 2 What is the result of Meiosis I?One chromosome of each homologous pair is distributed to a different daughter cell, a reduction division has occurred. SO the daughter cells are haploid but are still in the form of sister chromatids Complete the chart by describing what happens in each phase of Meiosis II. Prophase IIMetaphase IIAnaphase IITelophase II-spindle apparatus forms-one spindle fiber attaches to centromere of each sister chromatid-replicated chromosomes line up at metaphase plate -sister chromatids separate -daughter chromosomes moving to opposite side of cell-chromosomes arrive at opposite side of cell-nuclear envelope forms around each haploid set of chromosomes **Cytokinesis What is the result of Meiosis II?Four haploid cells, each has one type of chromosome Now that you know what goes on Meiosis I and Meiosis II, put them together and DRAW out the whole process of Meiosis. This will help you remember it. Exam 3 Worksheet 3What does the G1 checkpoint check for?Is the cell size is adequate Nutrients are sufficient Social signals are present DNA is undamaged What does the G2 checkpoint check for?Chromosomes have replicated successfully DNA is undamaged Activated MPF is present How many M-phase checkpoints are there and what do they check for?2 checkpoints 1 checks that the chromosomes have attached to the spindle apparatus the other checks that the chromosomes have properly segregated and MPF is absent Mature cells get permanently stuck in the G1 phase. What is this arrested state called?G0Mature cells are nondividing cellsCell stops dividing permanently*real life application: some cells are terminally differentiated. Neurons and red blood cells are examples of terminally differentiated cells. When these cells reach their final mature state, they do not need to divide ever again. For this reason, the cells leave G1 and enter an alternative state called G0 (read G-zero) where they stop dividing permanently. Not all cells can enter the G0 phase. Cells in G0 may not undergo mitosis, but they are still very metabolically active. For example, half of a human brain consists of neurons that are in G0. Yet the brain consumes about 25% of the body’s metabolic energy each day You did not need to know this it is just an example that may help some people.What about cell cycles can vary among different cell types?The length of the cell cycleVariation in the length of G1 phase is responsible for differences In the simplest way possible, how would you describe to someone what cancer is?Out of control cell division due to cell cycle checkpoints failing (usually G1) What two types of defects can cancerous cells have?Defects that make the proteins required for cell growth active when they should not be Defects that prevent tumor suppressor genes from shutting down the cell cycle*note that both of these result in out of control cell growth 8. Describe the difference between a benign tumor and a malignant tumor. Benign tumors are noninvasive and noncancerous Malignant tumors are invasive, cancerous, can spread through body via the blood or lymph, initiate secondary tumors when cancer cells detach from the original tissue and invade other tissues, what is this called?Metastasis what is the difference between homologs and sister chromatids?Homologs consist of 1 paternal chromosome and 1 maternal chromosome (1 from mom and 1 from dad) that are similar in size, shape and gene content Sister chromatids are two identical chromatid copies in a replicated chromosome what is a bivalent (or tetrad)?Homologous replicated chromosomes that are joined together during prophase I and metaphase I of meiosisAt the end of Meiosis I, are we left with 2 diploid or haploid cells?Haploid At the end of Meiosis II, are we left with 4 diploid or haploid cells?Haploid Draw out the process of Meiosis WITHOUT LOOKING AT YOUR NOTES. Do your best! This will help you figure out what you are not understanding and what you need to work on. Also do your best do describe what is happening in each phase. Early prophase ILate prophase IMetaphase IAnaphase ITelophase I -chromosomes condense-spindle apparatus forms-nuclear envelope breaks down -homolog pairs come together in a pairing process called synapsis-non-sister chromatids begin to separate- chiasmata are formed so crossing over occurs btwn non-sister chromatids -line up at metaphase plate-paired HOMOLOGS separate -start to migrate to opposite poles-finish migrating to opposite poles-nuclear envelope forms **Cytokinesis takes places after this to divide the cell into 2 Prophase IIMetaphase IIAnaphase IITelophase II-spindle apparatus forms-one spindle fiber attaches to centromere of each sister chromatid-replicated chromosomes line up at metaphase plate -sister chromatids separate -daughter chromosomes moving to opposite side of cell-chromosomes arrive at opposite side of cell-nuclear envelope forms around each haploid set of chromosomes **Cytokinesis Meiosis and Mendel – Chapter 13 and 14 KEY Exam 4 Worksheet 4 First, a review from last time…What cell cycle checkpoint most frequently fails in cancerous cells?G1 What is the difference between a benign and malignant tumor?Benign is noninvasive and noncancerous Malignant is invasive, invading surrounding tissues, can give rise to other tumors How do malignant cells travel through the body?Lymphatic and circulatory systemsWhat protein actually triggers the production of S-phase proteins?E2FWhat are the components of an organism’s karyotype?Number of chromosomes the type of chromosomes that a particular organism has What is the relationship between homologous chromosomes and alleles?Alleles are gene that are encoding same trait, homologous is one from mom one from dad What does the term “ploidy” mean?How many copies of chromosomes Describe the main difference between Meiosis I and Meiosis II. In Meiosis I, homologs splitIn meiosis II, sister chromatids separate What splits when homologs split during Meiosis I?Synaptonemal complex When sister chromatids separate in Meiosis II, what is splitting apart?Cohesions What is forming when you see the Chiasma? What is occurring here?Tetrad (or bivalent)Crossing over occurs Why are you haploid at the end of Meiosis I?Because Meiosis I is when you are doing the reductive division; goes from diploid to haploid Daughter cells now only have 1 copy of each homologous chromosome Why are you still haploid at the end of Meiosis II? Because all you did in Meiosis II is break apart the sister chromatids Awesome video that explains Meiosis really well that you watched in class today!!! Watch this a lot to help you memorize it! Chapter 13 – Meiosis today… What is produced through asexual reproduction?Clones What causes genetic variation in sexual reproduction? Describe each. Independent assortment: you never know what side of Metaphase plate the homologous chromosomes will end up on. Separation and distribution of homologous chromosomes during Meiosis I can result in a variety of combinations of maternal and paternal chromosomes Crossing over: new combinations of alleles on the same chromosomes; combinations that did not exist in each parent Outcrossing: during fertilization; gametes from two different individuals combine to form offspring How is it possible for an organism that self-fertilizes itself to produce offspring that are genetically different?Still 2 copies of each chromosome so they can line up differently and be split up differently So they can still do crossing over and independent assortment If homologs or sister chromatids don’t separate completely, what is this mistake called?Nondisjunction What does nondisjunction result in?Aneuploid zygotes which means too few or too many chromosomes Typically do not survive to produce viable offspring Is this common?Yes. This happens in as many as 10 percent of meiotic divisions Down’s syndrome is an example of __trisomy__ and is caused by an extra copy of chromosome 21. Down’s syndrome occurs due to nondisjunction during Meiosis I, a result in the failure in the breakdown of what?The metaphase plateSynaptonemal complexCohesions Nuclear envelope Why would males be considered a disadvantage of sexual reproduction?Males are more prone to deleterious mutationsCompetition amongst males for mates lowers overall fitnessMales often produce aneuploidy spermMales do not directly reproduce What is the Purifying Selective Hypothesis?Anything that compromises your fitness is removed through the process of purifying selection Natural selection against deleterious alleles Ex: if you have a deleterious allele you will not survive as long or reproduce as often as someone who lacks that bad allele. What is the Changing-Environment hypothesis?Offspring that are produced by sexual reproduction are more likely to survive and produce offspring if the environment changes Sexually produced offspring can evolve quicker Chapter 14 – Mendel and the Gene Who is Gregor Mendel?What plant did he use for his experiments?Common garden peas Describe blending inheritance vs. inheritance of acquired characteristics. Blending: parental traits blend such that their offspring have intermediate traits Acquired characteristics: parental traits are modified then passed on to their offspringWhat characteristics do model systems usually have?Easy to growReproductive cycle is short Produces large numbers of seedsMatings are easy to control Traits are easily recognizable How did Mendel arrange matings?Mendel prevented self-fertilization by removing male reproductive organs Then he used pollen from other plants to fertilize these flowers thereby performing cross-fertilization What traits did Mendel look at in the peas? Seed shape Seed color Pod shape Flower color Flower and pod position Stem length *end with “The Monohybrid Cross”Mendel and the Gene Exam 4 Worksheet 4 A little review… What is the KEY difference between meiosis and mitosis? Mitosis produces identical daughter cells (ex: skin cells), undergoes 1 division Meiosis produces 4 genetically distinct daughter cells, undergoes 2 divisions, Meiosis undergoes reduction division in Meiosis I Why is meiosis a “reduction division”? Homologs are separated; goes from diploid to haploid What are the three mechanisms we discussed that generate diversity during meiosis and how do they generate diversity?Crossing over (nonsister chromatids are exchanging genetic material), independent assortment (chromosomes from mom and dad line up and randomly move around the metaphase plate) and fertilization(many different unique types of gametes are produced and it’s random which ones actually get to fertilize)How do failures in meiosis occur and what is the result of these failures?Synaptonemal complex not breaking apart in Meiosis ICohesions not breaking apart in Meiosis II Results of these failures usually results in death of baby What is the failure in meiosis called??Nondisjunction What is an adjective to describe a gamete produced after failure in meiosis?Aneuploid gametes; gametes with an irregular number of chromosomes What is an example of a disease resulting from failures in meiosis?Down’s syndromeWhy might asexual organisms have an advantage over sexual organisms?Asexual organisms do not have male so they can all reproduce What are two hypothesis that predict sexual reproduction may have an advantage over sexual reproduction?Purifying hypothesisChanging environment hypothesis How have scientists tested the advantage of sexual reproduction?Roundworms; exposed half to pathogen and that half switched from asexual to sexual reproduction because they needed genetic diversity to survive What is a trait?Physical characteristic of an organism What two hypothesis of inheritance were widely believed at the time Mendel started his work?Blending hypothesis (red dad + white mom = pink)Acquired characteristics (characteristics from mom and dad are modified and passed on to offspring)Why did Mendel choose the garden pea for his experiments?Reproduced quickly and easily Life cycle short Easy to take care of Small Easy to control fertilization by emasculating the flowers What is the distinction between phenotype and genotype?An organism's?genotype?is the set of genes that it carries. An organism's?phenotype?is all of its observable characteristicsToday’s material… What does F1 stand for?First filial generation, first generation after parental generation Describe the meaning of dominant and recessive traits. For a recessive?allele to produce a?recessive?phenotype, the individual must have two copies, one from each parent. An individual with one?dominant?and one?recessiveallele for a?gene?will have the?dominant?phenotype.Describe what a reciprocal cross is. A pair of crosses between a male of one strain and a female of another, and vice versaex: male is round and female is wrinkled first cross, then female is round and male is wrinkled second cross. We do this to see if the traits we are testing are linked to whether it is male or female What do we now identify as the “particles” in Mendel’s hypothesis of particulate inheritance?GenesChromosomesNucleotidesGenomes What are alleles?Different versions of each gene Do individuals with the same genotype always have the same phenotype? Why or why not?No. Environmental conditions will cause them to appear different Ex: twins can be different heights due to different nutrition A gene that has two copies of the same allele is referred to as __homozygous__. A gene that has two different alleles is referred to as __heterozygous__. True or false: dominant alleles always mask recessive alleles when they are paired together. What is the difference between a monohybrid cross and a dihydrid cross?Monohybrid: crossing a single trait (ex: round vs wrinkled)Dihybrid: crossing two traits (ex: round vs wrinkled AND yellow vs green)Did Mendel’s experiments support the hypothesis of independent assortment or dependent assortment?Independent assortment Means that different traits don’t depend on each other What is a testcross?a parent that is homozygous recessive for a particular trait is mated with a parent that has the dominant phenotype but unknown genotype While doing a testcross, what are the possible genotypes of the unknown parents?Either heterozygous or homozygous dominant What is a wild type?The most common phenotype for each trait Mendel crossed a wrinkled pea pure line to an individual with round peas but an unknown genotype. All of the progeny had round peas. What was the unknown individuals genotype?Hint: draw a punnet square! RR What is the difference between a mutation and mutant?Mutation: phenotypes that differed from the wild type, results from the change in a gene Mutants: individuals with traits attributable to mutation Genes on autosomes are said to show __autosomal inheritance__. What is sex-linked inheritance?The pattern of inheritance that may result from a gene located on either the X or Y chromosome What is the different between sex-linked and linked genes?Sex-linked means that it is on a sex chromosome Linked genes are often transmitted together during gamete formation Multiple allelism is when genes have more than two alleles. When more than two two distinct phenotypes are present in a population due to multiple allelism, the trait is called what?Polymorphic What is the difference between incomplete dominance and codominance?Incomplete: The heterozygotes have an intermediate phenotype Codominance: a heterozygous organism that displays the phenotype of both alleles of a gene Genes that influence many traits are __pleiotropic__. What is the difference between a discrete and quantitative trait?Discrete traits are characteristics that are qualitatively different (ex: green vs yellow, nothing in between)Quantitative traits are traits that are not discrete but fall into a continuum (ex: height, weight)What is a pedigree?Family tree used to analyze existing human crosses Record gender and genetic relationships among individuals in a family Help reveal patterns of inheritance Do males or females determine the gender of the zygote?Males Because egg will have X chromosome Sperm will have X or Y XX will be female, XY will be male EXAM 4 REVIEW is Monday, March 20th at 4:10pm in GILMAN 1002. Will you be there?Yes Yes ................
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