Cell Cycle Unit 3

Cell Cycle ========== - Every phase but the miotic phase is called the interphase - Miotic Phase - Division phase - G1 phase - Growth phase - Replication - S phase - Synthesis phase - Replication happens - G2 Phase - Second growth phase (short...

Cell Cycle ========== - Every phase but the miotic phase is called the interphase - Miotic Phase - Division phase - G1 phase - Growth phase - Replication - S phase - Synthesis phase - Replication happens - G2 Phase - Second growth phase (shorter) - Maximum size - Prepare for division - G0 - Non dividing cell - May be temporary or permanent Mitotic Phase ============= - Mitotic phase of the cell cycle involves a pair of related processes: mitosis and cytokinesis - Mitosis: - Division of the nucleus that results in two identical nuclei - Cytokinesis - Division of the cytoplasm that results in two daughter cells - (Usually occurs in conjunction with mitosis but not always) Discussion Question ===================  A. 1 is rapid increase in DNA so it is the S phase B. 3 Has rapid decrease so it is the correct answer C. 4 has low count of DNA but is staying the same probably the G1 phase D. 2 Is staying the same so it is probably the G2 phase If a fruit fly zygote goes through mitosis four\ times but never undergoes cytokinesis, which\ of the following outcomes would be observed? A. eight cells that each contain a nucleus B. one cell that has sixteen identical nuclei C. sixteen cells that each contain a nucleus D. one cell that has eight identical nuclei One cell because without cytokinesis the cell will not actually divide 124816 Mitosis: Prophase ================= (chromosomes already replicated) - Chromosomes will condense into compact structures - Yellow thing is called a spindle - Protein structure that moves chromosomes Prometaphase ============  ===================== - Nuclear envelope disappears - The blue ring - Spindle will attach to the chromatids - Attaches to the centromere through the kinetochore - The center of the chromosome but on the different ends - Pulls on the two ends of the chromosome Metaphase ========= - Chromosomes align in the center of the cell Anaphase ========  - Chromatids separate and get pulled to opposite ends - The moment they break apart they are called chromosomes - Because they are now acting independently without each other Telophase ========= - Cell is done nearly done dividing - Cell membrane reassembles around each set of chromosomes, forming two separate nuclei - Chromosomes begin to decondense back into a chromatin state Cytokinesis ===========  - Contractile ring - Protein ring - Very similar to muscle tissue Discussion Question =================== Cytokinesis differs in plants and animals due\ to the presence of which structures in plants? A. vacuoles\ B. chloroplasts\ C. cell membranes\ D. mitochondria\ E. cell walls - Starts with the cell plate in the middle - Builds onto it until it separates into two nuclei - Like splitting a room in half by building a wall in the middle How many chromosomes does a cell with 64\ chromosomes during the G1 phase of the cell\ cycle have during prometaphase of mitosis?\ A. 32 B. 128. C. 64 D. 256 E. none - Go into synthesis twice as many chromatids but still only 64 chromosomes - Will not have twice as many chromosomes until anaphase when the chromosomes split their chromatids which make the chromatids technically chromosomes Mitotic Division ================ - Used for: - Growth - Regeneration - Repair and replace - Asexual reproduction - Plants and fungi Mitotic Division ================ - Several checkpoints regulate the cycle by pausing cell division if certain conditions are not yet satisfied - Checkpoints failures lead to uncontrolled division and cancer - G1 phase - Appropriate cell size before it can move on - Signaling - DNA damage - G2 phase - Did the chromosomes get completely replicated - DNA damage - M phase - If the spindles are not attached to the chromosomes correctly - Spindles should detect that there is not even attachment and should pause the M phase - If a problem does occur 2 options: - Stop and fix it - Apoptosis (cell death) - If cancer does still happen it is because the molecules in the checkpoints that look for issues to pause/stop the cycle stop working. Discussion Question =================== If colchicine disrupts formation of the spindle,\ how would this substance affect the cell cycle? A. Cell will not commit to DNA replication - Replication is in the "S" phase B. Cell cycle will stop before mitotic phase. - Spindle is not a condition until metaphase C. Colchicine will not impact the cell cycle. D. Cell cycle would stop during metaphase. - M checkpoint will stop it E. Cell will exit the cycle into the G0 phase. Homologous Chromosomes ====================== - Homologous chromosomes are same size, contain same genes, and pair for meiosis - One of each pair is inherited from dad (paternal) and one from the mom (maternal) - Y chromosome is not homologous - 22 chromosomes are called autosomes and last 23^rd^ pair is called the sex chromosome - Sex chromosome creates the gender - XY Man XX Women Alleles ======= - Gene is a section of DNA that codes for one or more related proteins or RNA - Alleles are different forms of the same gene - DNA sequence is not the same HBA is a gene on chromosome 16 in humans\ that codes for part of hemoglobin. This gene\ was duplicated during our evolutionary past\ into HBA1 and HBA2. How many copies are\ found in a somatic cell during the G1 phase? 4\. Because both mom and dad have it (that's just how that works for genes there's always two) and then it got duplicated so there's another 2 1 from each parent. Ploidy ====== - Ploidy is the number of chromosome SETS present in the nuclei - Haploid: single chromosome set (n) - Diploid: two chromosome set - Polyploid: greater than two sets of chromosomes (3, 4n, 5n, etc.) - Most crop/plants are polyploid Diploid plants with somatic cells that contain\ 18 chromosomes are used to produce triploid\ plants (3n). How many chromosomes will be\ found in the somatic cells of a triploid plant? 27\. 2n = 18 n = 9 3(9) = 27 Meiotic Phase ============= - Meiosis (my-osis) is division involved in sexual reproduction that - Results in four different nuclei that are each half of the original ploidy (example: 2n to n). - Cytokinesis is division of the cytoplasm that\ results in two daughter cells (happens twice). - As for mitosis, DNA replication occurs prior\ to meiosis (during the S phase of interphase). - None of them are identical Meiosis 1 ========= - 1 2 - Major differences happen here - Synapsis (unique to meiosis) - Maternal and paternal (homologous pairs) are attached to each other - Recombination (crossover) - When the chromosomes exchange segments with each other to share DNA - Result is recombinant chromosomes - Chromosomes that are no longer purely maternal or paternal but instead a combination of both - Crazy amount of replication - Where it is occurs in the chromosome is random End of Meiosis 1  - Homologous pairs are separated from each other Meiosis 2 ========= - Identical to mitosis - Have half the ploidy of the original cell - All daughter cells are different When is the ploidy reduced during meiosis? End of meiosis 1 When the homologous pairs are pulled apart  CADE Genetic Variation ================= - Offspring from sexual reproduction, which requires meiosis during the life cycle, share traits with parents and siblings yet are also genetically distinct - Independent assortment - Fertilization - Recombination Independent Assortment ====================== - Alignment of homologous chromosome pairs during meiosis 1 is independent and random Discussion Questions ==================== Somatic cells of a diploid organism contain 8\ chromosomes during the G1 phase. Assuming\ no recombination during meiosis, how many\ different gametes can the organism produce?\ A. 16 B. 128 C. 32 D. 256 E. 8 It\'s because even with replication it's only just red or black not small black big black and small red big red because during replication they are the exact same. Fertilization (gamete fusion) also generates an\ incredible amount of genetic variation. Due to\ independent assortment and fertilization, how\ many different kids can two humans produce?\ A. 4.2 million\ B. 70.4 trillion\ C. 16.8 million\ D. 35.2 trillion\ E. 8.4 million Recombination ============= - Recombination during meiosis 1 produces chromosomes with different combinations of alleles than those found in the organism Sex Paradox =========== - Asexual reproduction is far more efficient for producing offspring than sexual reproduction - Because you need two parents both a mom and a dad - There is not a lot of variation only variation is due to mutation Discussion Questions ==================== Which of the following is the original source\ of genetic variation for sexual reproduction?\ A. mutation\ B. recombination\ C. independent\ assortment\ D. fertilization Jumper ants have a single pair of chromosomes\ yet produce offspring with a significant amount\ of genetic variation. Which of the following will\ contribute the most to variation in this species?\ A. mutation\ B. recombination\ C. independent\ assortment\ D. fertilization Nondisjunction ============== - An error that occurs and chromosomes are incorrectly distributed to the daughter nuclei - Trisomy - When you end up with 3 chromosomes instead of 2 - Results in down syndrome - Klinefelter syndrome/XXY - When you have 2 Xs and a Y - Infertility Discussion Question =================== Two parents have a child with\ Down syndrome. When did the\ nondisjunction likely happen?\ A. meiosis I in parent \#1\ B. meiosis II in parent \#2\ C. meiosis II in parent \#1\ D. meiosis I in parent \#2 If a diploid cell has four chromosomes before\ meiotic division, how many chromosomes will\ daughter cells receive if a nondisjunction that\ affects one chromosome occurs in meiosis II?\ A. 2, 2, 4, 0\ B. 3, 3, 1, 1\ C. 2, 2, 3, 1\ D. 3, 3, 2, 0 Because only one chromosome is affected Gametogenesis ============= - Just means gamete production - Egg cells are way bigger than sperm cells - Egg cells are more likely to go through nondisjunction because they are so old (made in womb while sperm is made constantly) - This is why younger mothers are more likely to produce healthy babies Discussion Question =================== Jacobs or XYY syndrome is a condition where\ men have two Y chromosomes. This syndrome\ is likely due to an error during which process?\ A. meiosis I in father\ B. meiosis II in father\ C. meiosis II in mother\ D. meiosis I in mother\ E. mitosis in embryo - Mosaic - An organism with different chromosomes in different cells of their body Life Cycle ==========  Process 1: Meiotic Division Gamete ploidy: 1n Process: Fertilization Zygote ploidy: 2n Process: Mitotic Division Adult ploidy: 2n Discussion Question If a person goes outside without sunscreen and\ UV radiation from the sun mutates the DNA in\ their skin cells, who will inherit the mutations?\ A. all children\ B. daughters but not sons\ C. some random children\ D. sons but not daughters\ E. no children Plants - Happens in 2 phases - These two phases are sporophyte and gametophyte (usually think about sporophyte) - Sporophyte ploidy: 2n and then it undergoes meiotic division to make a bunch of sprouts - Then the sprouts undergo mitotic division to make gametophyte and they make sperm or eggs - Fertilization happens and from there it is pretty similar to animals Sporophyte ploidy: 2n Process: Meiotic division Spore ploidy: n Process: Mitotic division Gametophyte ploidy: n Gamete ploidy: n Process: Mitotic division Process: Fertilization Zygote ploidy: 2n Process: Mitotic Division