Exam 3 Study Guide
Exam 3 Study Guide EBIO 1210-001
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This 25 page Study Guide was uploaded by Tatiana Tabares on Friday November 13, 2015. The Study Guide belongs to EBIO 1210-001 at University of Colorado taught by Dr. Barbara Demmig-Adams in Fall 2015. Since its upload, it has received 202 views. For similar materials see General Biology 1 in Biology at University of Colorado.
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Date Created: 11/13/15
EXAM 3 ______________________________________________________________________ Cell Cycle Cell division: the cell cycle and the functions of different types of cell division 1. What are the functions of mitotic cell division ● The vast majority of cells in the adult body are not dividing! ● To renew naturally used up cells ● To replace cells after injury ● During development ● During reproduction of single celled organisms ● Most cells in your body never go past G1 they go to G0 (part of interphase) ○ These cells are not going to progress through the cycles ○ Are performing specialized functions ○ Doing things for you, to keep you alive List several biological functions or processes in which cell division plays a key role. 1. What are the functions of mitotic cell division ● The vast majority of cells in the adult body are not dividing! ● To renew naturally used up cells ● To replace cells after injury ● cuts, scrapes ● During development ● zygotes ● During reproduction of single celled organisms Explain reasons why the cell cycle must be regulated in order for any human to be healthy during growth, development, and maintenance of the body. What happens when cell division goes WRONG? ● Cancers ○ A tumor grows from a single cancer cell ○ Cancer cells invade neighboring tissue ○ Cancer cells spread through lymph and blood vessels to other parts of the body ○ A small % of cancer cells may metastasize to another part of the body Understand the concept of “checkpoints” as applied to the cell cycle; explain how checkpointing can be accomplished with molecules Regulation of the Cell Cycle 1. Checkpoints ● Mitotic checkpoints: move on to the next phase only if conditions are right ● Prevents sick or precancerous cells from dividing and maintains proper cell number Checkpoint sensing mechanisms monitor: ○ Progression of the current phase ○ DNA integrity ○ Cell density ○ Cell anchorage ● what you are anchored to or attached too ● Multiple checkpoints within the cell cycle to regulate going forward ○ G1 checkpoint ● sends things that need to remain in G0 back, they have important functions that keep you alive ○ G2 checkpoint ○ M checkpoint ● Like stoplights or gates 2. he cell cycle is regulated by proteins in the cytoplasm Cyclin Accumulation ● Cyclin ○ protein ○ sounds like cycle is a protein that has a read out or determines where it is in the cycle ○ during S and G2 ○ can bind to other proteins ● like CDK ● CDK enzyme that binds with cyclin ○ becomes active which makes it a "mitosis promoting factor" ○ happens during S and G2 ● Cyclin is degraded during M and G1 Important take home message of the Cyclin accumulation Concentrations of proteins in the cytoplasm regulate the cell cycle Cyclins are ONE EXAMPLE > there are other checkpoints and other molecules at work Cyclin and checkpoints ● If anything is out of whack, the cell cycle is stopped by: ○ increasing rate of cyclin degradation ○ inhibiting interaction of cyclin and CDK ● Both of these processes act to prevent the cell from crossing the checkpoint between G2 and the mitotic phase! Describe how cancer relates to checkpoints, mutations, and loss of proper regulation of the cell cycle. Genetic material inside cells: the molecules of heredity and the processes they undergo during the cell cycle and different types of cell division 2 Regulation of the Cell Cycle 1. Checkpoints ● Mitotic checkpoints: move on to the next phase only if conditions are right ● Prevents sick or precancerous cells from dividing and maintains proper cell number What happens when cell division goes WRONG? ● Cancers ○ A tumor grows from a single cancer cell ○ Cancer cells invade neighboring tissue ○ Cancer cells spread through lymph and blood vessels to other parts of the body ○ A small % of cancer cells may metastasize to another part of the body Cancer cells → usually continue to divide well beyond a single layer, forming a clump of overlapping cells. They do not exhibit anchorage dependence or densitydependent inhibition Anchorage dependence → to divide they must be attached to a substratum, such as the inside of a culture flask or the extracellular matrix of tissue. Densitydependent inhibition → a phenomenon in which crowded cells stop dividing; one single layer. Cancer cells do not stop with the normal signals that regulate the cell cycle. They continue to divide regardless of the cell cycle checkpoints. Explain what a chromosome is to someone who is not a biologist; describe where chromosomes are in the cell and what they are made of. Chromosome → A cellular structure consisting of one DNA molecule and associated protein molecules. A eukaryotic cell typically has multiple linear chromosomes, which are located in the nucleus. A prokaryotic cell often has a single, circular chromosome, which is found in the nucleoid, a region not enclosed by a membrane. They are also the structure in which DNA molecules are packaged. Chromatin → the entire complex of DNA and proteins that is the building material of chromosomes ______________________________________________________________________ Mitosis and Meiosis Describe what happens to chromosomes during the cell cycle and mitosis. CELL CYCLE Interphase G1, S, G2 Mitotic Phase When cells are not dividing: interphase Cell cycle from the time a cell is formed (from the division of its parent cell), to the time it undergoes its own division into two cells Most of the time is spent in interphase ( G1 [growth], S [synthesis], G2 [growth]) then Mitotic phase The Mitotic Phase (where division actually happens) Mitotic Phase (M Phase) ● When the cell divides ● Has 2 parts ○ Mitosisdivision of nucleus and nuclear material ○ CytokinesisDivision of rest of cell The organization of genetic material in animal cells ● Nucleus ○ Multiple chromosomes (46 in most) [during G1] ● 1 DNA molecule ● accessory proteins During Replication of DNA (happens during S phase of interphase) First stage of mitosis ● Duplication of genetic material ● One DNA molecule is made into 2 DNA molecules ● Separation of the sister chromatids (the duplication of DNA is still stuck together and considered to be 1 chromosome) occurs in Mitosis phase MITOSIS ● Prophase 1. Chromosomes condense > they become supercoiled for efficient movement during subsequent processes 2. Preparation of the mitotic spindle > a molecular scaffold that will help guide chromosomes Second stage of mitosis ● Prometaphase 1. Nuclear membrane breaks down 2. Spindle attaches to chromosomes Third stage of mitosis ● Metaphase Chromosomes line up in the middle of the cell Fourth stage of mitosis ● Anaphase Sister chromatids separate, pulled by spindle Fifth stage of mitosis ● Telophase 1. Nuclear membranes reform 2. Cytokinesis can begin at the same time Describe what happens to chromosomes during meiosis. ● My toes do mitosis my ovaries do meiosis ● Meiosis = the division of a diploid cell leading to the eventual production of ○ gametes only have 23 chromosomes and are haploid 3) A detailed look at meiosis First Cell Division = Meiosis 1 ● We separate homologous chromosomes ● 2 cells with 2 sister chromosomes stuck together ● Looks very different to Mitosis 2nd Cell Division = Meiosis 2 ● Sister chromatids are separated Early in Meiosis I: ● Homologous chromosomes loosely pair up, aligned gene by gene ● In crossing over, nonsister chromatids exchange homologous DNA segments ○ Importance will become apparent soon Middle of Meiosis I: ● Pairs of homologous chromosomes line up in the middle of the cell, with one chromosome facing each pole ● Spindle attaches to chromosomes Compare and contrast the similarities and differences between mitosis and meiosis. Meiosis II is very similar to mitosis at the end: 4 daughter cells, all haploid, all genetically different Question Mitosis Meiosis Preceded by replication of Yes Yes chromosomes? # of rounds of cell division 1 2 # of daughter cells 2 4 # of chromosomes in daughter Same Half cells compared to parent cell daughter cells genetically Yes No identical to parent cell? sister cells thus produced Yes No identical to one another? happens in diploid cells, both (depending diploid (because you need haploid cells, both, or neither? on organism) 2 chromosomes to split them) crossing over No Yes p. 200 figure 10.9b Summary of diff. and similarities of Mitosis and Meiosis What is MAJORLY different here from what you saw mitosis? ● Prophase I ● Anaphase I ○ Lined up 2 by 2 because the chromosomes are still in pairs ○ In mitosis they are lined up 1 by 1 because they are no longer in pairs of chromosomes ○ The way that they line up does not affect the way the next one line up, example red on top blue on bottom, blue on top red on bottom ○ The chromosomes are being separated ○ Chromatids are NOT being separated (sister chromatids remain attached) Describe the relationship between a DNA molecule, a chromatid, and a chromosome. Chromosome → A cellular structure consisting of one DNA molecule and associated protein molecules. A eukaryotic cell typically has multiple linear chromosomes, which are located in the nucleus. A prokaryotic cell often has a single, circular chromosome, which is found in the nucleoid, a region not enclosed by a membrane. They are also the structure in which DNA molecules are packaged. Chromatin → the entire complex of DNA and proteins that is the building material of chromosomes Define and understand the concept of ploidy; describe the cyclic changes in ploidy that are universal to the life cycles of all sexually reproducing organisms Polyploidy → a chromosomal alteration in which some organisms have more than two complete chromosome sets in all somatic cells. Aneuploidy → The zygote will have an abnormal number of a particular chromosome. The concept of Ploidy in general is when an organism has poly “more than one” chromosome of a certain kind. More than is needed. There are several different kinds of ploidy. Describe how a zygote has some chromosomes that were “paternally inherited” and some chromosomes that were “maternally inherited” A Zygote gets two haploid gametes (n=23) from its mother’s ovaries and its father’s testes. Together they form a diploid (2n=46) single celled Zygote These haploid gametes carry 23 chromosomes each with the genetic DNA information that will form the Zygote. ______________________________________________________________________ Mendelian Genetics Explain how and why the chromosomal makeup of an offspring produced by sexual reproduction differs from that of its parents In humans, ovaries and testes produce haploid gametes by meiosis, each gamete containing a single set of 23 chromosomes (n = 23). During fertilization, and egg and sperm unite, forming iploid 2n 46 singlecelled zygote hich goes through mitosis and becomes a multicellular organism through cell division. Describe four main processes that create genetic variation in the offspring produced from sexual reproduction Genes, heredity, and Mendelian genetics: the foundations of our understandings about genetic variation in populations and how it is passed on from one generation to the next ● The behavior of chromosomes during meiosis and fertilization reshuffles alleles and chromosomes every generation ● Four mechanisms contribute to genetic variation in offspring of sexual reproduction: ○ Mutations = change in DNA sequence ○ Independent assortment of chromosomes ○ Crossing over (early in Meiosis I) ● Each possibility is equally likely ______________________________________________ Genotype Gene makeup, what it is made up off Phenotype Appearance, what it looks like ● The view provided by (simplified presentation) Mendel's pea experiments: ○ one gene → one character ○ one allele → one phenotype ● e.g., flower color gene → color of flower ● e.g, P allele purple flower ○ two alleles of each gene, one completely dominant, the other recessive ● e.g, P dominant to p Define biological inheritance; compare and contrast the hypotheses of “blending inheritance” and “particulate inheritance”. Blending inheritance = traits of offspring will be an average of the traits of the parents a. > opposite of blending inheritance = particulate inheritance Match the specifics of Mendel’s work with corresponding general steps in the scientific method. Mendel used the scientific method to test his four hypothesis on genetic inheritance. He also used experimentation, data, questions, and research. Through this he was able to establish the Law of Segregation and the Law of independent Assortment Explanatory framework = multiple internally consistent hypothesis that together explain general phenomena of interest. In science this is also called a theory. Describe alternative hypotheses that Mendel formulated and tested about inheritance; describe what each hypothesis predicted Mendel should have observed; relate his actual findings to the falsification of some hypotheses and support for others. Mendel’s Theory: 4 related hypotheses → these can be related to what we know about genes and chromosomes!! 1. Alternative versions of heritable "particles" (i.e., different alleles of the same genes ) account for variations in inherited characters 2. For each character an organism inherits two alleles, one from each parent 3. If the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance, and the other (the recessive allele) has no noticeable effect on appearance 4. "Law of segregation" = the two alleles an individual possesses for a heritable character separate (segregate) during gamete formation and end up in different gametes Relate Mendel’s “law of segregation” to the behavior of genes and chromosomes during meiosis. Mendel's "Law of segregation" is used to construct a Punnett square "Law of segregation" = the two alleles an individual possesses for a heritable character separate (segregate) during gamete formation and end up in different gametes Relate Mendel’s “law of independent assortment” to the behavior of chromosomes during meiosis; describe a situation in which the “law” of independent assortment would be violated. Gene Linkage and mapping Law of Independent Assortment ● Alleles of genes on nonhomologous chromosomes assort independently during gamete formation. Combinations of alleles that are non parental are called "recombinant" ______________________________________________________________________ Other information on Mendelian Genetics ● with 2 alleles, P and p, there are 3 possible genotypes: PP, Pp, and pp ● PP and pp are homozygous genotypes; individuals with these genotypes are called homozygotes ● Pp is the heterozygous genotype = genotype carried by heterozygotes What about multiple characters? Are they inherited together or separately 1. Seed Color: 2. Possible phenotypes = Yellow OR green 3. Yellow is dominant to green 4. Seed Shape: 5. Possible phenotypes = Round or wrinkled 6. Round is dominant to wrinkled 1. Strict dependent assortment 2. Independent assortment Patterns of inheritance different from those discussed so far can be caused in many ways. Just to name a few ○ Lack of complete dominance by one allele ○ A gene has more than two alleles ○ A gene produces multiple phenotypes ○ Multiple genes affect a single phenotype ○ Environmental circumstances affect the phenotype ● A dominant allele does not subdue a recessive allele; alleles don't interact Correcting misconceptions about dominance ● Dominant alleles are NOT necessarily the most common alleles ● Dominant alleles are not necessarily the "best" ○ e.g. polydactyly (extra digits) ○ e.g. Huntington's disease caused by dominant allele of a gene found on chromosome #4 Synthesis: Genes on Chromosomes ● Mitosis: replication and division of chromosomes to multiply cells ● Meiosis: replication and division of chromosomes to make gametes ● Mendel: the particulate theory of inheritance ________________________________________________________ ● Humans and many other species have chromosomal sex determination ● Birds and Butterflies demonstrate the ZW chromosomal system ○ In the human system, females usually have two "X" chromosomes, males usually have one "X" and one "Y" ○ The females have the two different chromosomes What consequences might sex chromosomes have for patterns of inheritance and gene expression and gene expression?? Patterns of inheritance in mammals (and other XY systems) ! from female parent from male parent allele on X passed on to either sons or passed on ONLY to chromosome daughters with probability 1/2 daughters with probability 1 ("Xlinked") allele on Y typically not possessed by females passed on ONLY to sons chromosome with probability 1 ("Ylinked") Genes on Chromosomes Outline 1. Mendelian inheritance has its basis in the behavior of chromosomes 2. Genes on chromosomes 3. Gene linkage and mapping The Fruit Fly ● They breed at a high rate ● A generation can be bred every 2 weeks ● They have only four pairs of chromosomes ● Males are XY and females are XX ● By studying them carefully, rare "mutant" phenotypes could be identified that were different from the normal "wild type" __________________________________________________ (in the junior example the recombinant combination are the gametes produced with genotypes Ab and aB it is a combo he did not inherit!) Gene Linkage ● Each chromosome has hundreds of thousands of genes ● Genes located on the same chromosome that tend to be inherited together are called linkage genes Recombination of Linked Genes Morgan Discovered that: ● Body color and wing phenotype were often inherited together: offspring usually had the same combos of phenotypes as one of the parents ● BUT, linkage was incomplete , as evident from recombinant phenotypes (combos different from parental types) ○ genes on the same chromosome Some process must sometimes break the physical connection between genes on the same chromosome In 1913, Sturtevant mapped genes without modern sequencing tools and, indeed, without knowledge that DNA was the hereditary molecule! Genetic Map Info on recombination frequencies can be used to create these HOW? > Assume that genes that are farther apart will show higher recombination frequencies Gene Mapping : Some useful terms ● Linkage map = genetic map of a chromosome based on recombination frequencies ● Notion of distance: map units; one map unit = 1% recombination frequency ● Map units indicate relative distance and order, not precise locations of genes Recombination frequency = (# recombinants / total # of offspring) x 100 Recombinant is when the phenotypes (the letters) do not match those of either of the parents ___________________________________________________________________ DNA Use data from a testcross to calculate recombination probabilities in a linkage map. 3 DNA and its replication: the molecular processes that enable genetic information to be passed on from cell to cell, and from generation to generation Know the basic structure of DNA: know its monomers and the three chemical pieces of an individual monomer. Based on the work of Franklin, Watson, Crick, Meselson , Stahl, Hershey, Chase, and many others, we now know that: 1. DNA is a double stranded molecules 2. The two strands are complementary, and together wind around in the form of a double helix. DNA is deoxyribonucleic acid A Nucleic Acid → is a polymer made of nucleotide monomers. A Nucleotide consists of: 1. a nitrogenous base 2. sugar 3. a phosphate group The sugar and phosphate group are the SAME for all nucleotides! The base is what varies! The sequence of nucleotides with different bases forms the code containing all hereditary information. There are only 4 nitrogenous bases > four possible nucleotides ● diff sequences of the 4 possible nucleotides are what make them different 1. Adenine 2. Guanine 3. Thymine 4. Cytosine Describe how the monomers of DNA are joined together—in terms of bonds between chemical groups—to make a polymer that we call a nucleic acid. q Know how hydrogen bonds hold a DNA molecule together and how the pattern of hydrogen bonding gives rise to Chargaff’s rule. Erwin Chargaff looking at chemical composition of DNA in any particular species: % adenine (A) = % thymine (T) % guanine (G) = % cytosine (C) ● Chargaff's Rule (above) In an UNPUBLISHED REPORT, Franklin postulated In an UNPUBLISHED REPORT, Franklin postulated ● The strands of DNA run in an antiparallel manner (one is upside down relative to the other one) ● The phosphate group in a single nucleotide is attached to the 5' (five prime) carbon atom of the sugar ● Sugar (deoxyribose) 3' (three prime end) ○ Like lego bricks top has dots (5') bottom has holes (3') ● adjacent nucleotides are linked phosphate to 3' carbon atom ● antiparallel arrangement allows proper base pairing ○ forms the backbone ○ hydrogen bonding keeps the two strands together and Chargaff's rule Understand what is meant by the polarity of a DNA molecule (5’ vs. 3’ ends), and why we say that two strands of a DNA molecule run “antiparallel” to one another. In an UNPUBLISHED REPORT, Franklin postulated ● The strands of DNA run in an antiparallel manner (one is upside down relative to the other one) ● The phosphate group in a single nucleotide is attached to the 5' (five prime) carbon atom of the sugar ● Sugar (deoxyribose) 3' (three prime end) ○ Like lego bricks top has dots (5') bottom has holes (3') ● adjacent nucleotides are linked phosphate to 3' carbon atom ● antiparallel arrangement allows proper base pairing ○ forms the backbone ○ hydrogen bonding keeps the two strands together and Chargaff's rule Note on directionality 1. DNA polymerase “reads” the parental template from 3’ to 5’ 2. DNA polymerase synthesizes the new strand by building onto the 3’ end of the primer or newly made strand → it builds the new strand 5’ to 3’ List the basic steps that must be accomplished in order to replicate DNA. A. Parental molecule B. Separation of parental strands into templates C. Formation of new strands complementary to template strands Describe how the DNA molecule itself acts as a “template” for accurate replication. A chromosomes composed of one chromatid = one DNA molecule A replicated chromosome composed of two chromatids = two DNA molecules ● Origin of replication ● Double stranded DNA molecule ● Bubble ● Replication fork DNA polymerases 1. match the right monomers with the template 2. catalyze formation of new sugar phosphate bonds 3. add 50 (eukaryotes) to 500 bacteria bases per second! Describe how consequences—such as differences between “leading” and “lagging” strands, and the loss of DNA from telomeres—arise from the DNA molecule’s polarity and the unidirectional synthesis performed by enzymes during replication. Leading strand → ● only one primer is needed ● continuous ● goes towards the replication fork Lagging strand → ● goes away from the replication fork ● several primers needed ● not continuous __________________________________________________ Helpful iClicker Questions and Answers: iClicker Question: Which of the following statements about interphase is FALSE? Very few of our cells are in interphase at any one time iClicker Question: Who has the highest percentage of cells in S phase (synthesis)? C) A Fetus iClicker Question: If an adult human being loses an arm in an accident, it does not regrow. Why not? D. Developmental processes for growing limbs are not reactivated when a limb is lost later in life. iClicker Question: Answer: True: Meiosis halves the number of chromosomes; fertilization restores the diploid number iClicker Question: A cell at the very beginning of meiosis has a total of 4 chromatids. What is "n" for the cell? Answer: 1 iClicker Question: At the very beginning of meiosis, a cell in your ovary/testis has 46 chromosomes. At the end of meiosis 1 (but before meiosis 2), this cell will have given rise to two cells that are each ___ and each have ___ chromosomes and ____ chromatids Answer: Haploid, 23,46 iClicker Question: 3 chromosomes were inherited from the child's mom and 3 from the child's dads. Which of the following best describes a pair of homologous chromosomes. Answer: C. Two chromosomes, one inherited from each parent, that have the same genes as each other. iClicker Question: Q: Disorders caused by recessive, sex linked alleles should be most commonly expressed in: Answer: b) female birds (ZW) and male humans (XY) ○ not homologous ○ recessive genes ○ you have inherited only one allele for each chromosome from these iClicker Question: The best explanation for the pattern of inheritance seen in the F2 generation is: Answer: The eye color gene is sex linked, on the X chromosome Counterintuitive > iClicker Question: Question: Given the conclusion from Morgan's work: If Morgan's parental generation had been white eyed FEMALES and red eyed MALES, than ____ of the males and ___ of the females in the F1 generation would have had white eyes. Answer: All;None
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