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Cell Division (OAT)
| Question | Answer |
|---|---|
| What are the two components of cell division? | Karyokinesis (nuclear division) followed by cytokinesis (cytoplasmic division). |
| What are homologous chromosomes? | Two copies of every chromosome in a diploid cell that form pairs. Humans have 46 chromosomes (23 homologous pairs). |
| What are centrosomes and what do they contain? | Cellular structures found in animal cells; each centrosome contains a pair of centrioles. |
| What do centrioles produce and what is their function? | Centrioles produce spindle fibers that separate sister chromatids during anaphase. |
| What are the two main phases of the cell cycle? | Interphase (G1, S, G2) and the Mitotic phase (mitosis and cytokinesis). |
| When does interphase begin? | After mitosis and cytokinesis are complete (when cells are replicated and physically separated). |
| What happens during G1 phase? | The cell increases in size; the G1 checkpoint ensures everything is ready for DNA synthesis; cells produce proteins, ribosomes, and mitochondria; organelles replicate. Most cell growth in volume occurs here. |
| What happens during S phase? | DNA synthesis — a second molecule of DNA is replicated from the first, creating sister chromatids. DNA replication occurs here, NOT during mitosis. |
| What happens during G2 phase? | Rapid cell growth continues; preparation of genetic material for cellular division; some organelles replicate. |
| What is G0? | An inactive state of cells not actively growing or dividing (e.g., nerve cells and cardiac cells). |
| What is the Surface to Volume (S/V) ratio and why does it matter? | When S/V is small (cell becomes too large), cellular exchange becomes difficult, leading to cell death or cell division to increase surface area. This is why cells are limited in how large they can grow. |
| What is the Genome to Volume (G/V) ratio and why does it matter? | As G/V decreases, the cell exceeds the ability of its genome to produce the proteins needed to regulate the cell, triggering division. |
| When does the spindle apparatus form? | During prophase. |
| What do microtubules attach to on chromosomes, and what is notable about this? | Microtubules attach to kinetochores on each sister chromatid — they do NOT attach directly to the chromosomes. |
| How do anti-tumor drugs act as microtubule inhibitors? | They stabilize microtubules, preventing chromosome and chromatid separation, causing cell cycle arrest (no cell division). |
| During which phase would a virus impacting the mitotic spindle most affect a cell? | The mitotic phase. |
| What happens during Prophase of mitosis? (chromosomes/chromatids count) | 46 chromosomes, 92 chromatids. The nucleus disassembles, nucleolus disappears, and chromatin condenses into chromosomes. The early mitotic spindle forms and the nuclear envelope fragments. |
| What happens during Metaphase of mitosis? (chromosomes/chromatids count) | 46 chromosomes, 92 chromatids. Chromosomes line up at the metaphase plate. Each metaphase chromosome consists of 2 attached sister chromatids, each complete with a centromere and attached kinetochore. |
| What happens during Anaphase of mitosis? (chromosomes/chromatids count) | 92 chromosomes, 92 chromatids. Microtubules shorten, pulling sister chromatids apart—once separated, each chromatid is counted as a chromosome, doubling the chromosome number. Chromosomes move to opposite poles, and each pole receives a full set. |
| What is disjunction and when does it occur? | pulling of chromosomes to opposite poles of cell. In mitosis, it occurs during anaphase when sister chromatids are pulled apart. In meiosis I, homologous chromosomes disjoin during anaphase I; in meiosis II, sister chromatids disjoin during anaphase II. |
| What is nondisjunction? | The failure of chromosomes or sister chromatids to separate properly during disjunction, resulting in daughter cells with an abnormal number of chromosomes (e.g., trisomy or monosomy). |
| What happens during Telophase and cytokinesis of mitosis? (chromosomes/chromatids count) | 92 chromosomes, 92 chromatids during telophase. Nuclear envelope re-forms, chromosomes decondense back into chromatin, nucleoli reappear. After cytokinesis, each resulting cell has 46 chromosomes and 46 chromatids. |
| What does meiosis produce? | Four non-identical haploid daughter cells from one diploid parent cell, by repeating nuclear division twice. |
| What separates in Meiosis I vs. Meiosis II? | Meiosis I — homologous chromosomes separate. Meiosis II — sister chromatids separate. |
| What are the three sources of genetic variation in meiosis/sexual reproduction? | 1) Crossing over during prophase I, 2) Independent assortment during metaphase I, 3) Random joining of gametes (which sperm fertilizes which egg). |
| What is crossing over? | Non-sister chromatids of two homologous chromosomes exchange genetic material during prophase I. |
| What is independent assortment? | During metaphase I, the random orientation of homologous chromosomes allows gametes to be produced with many different assortments of alleles. |
| What happens during Prophase I? (chromosomes/chromatids count) | 46 somes, 92 chromatids. Spindle forms, nuclear envelope breaks down. Homologous chromosomes pair (synapsis) to form tetrads, enabling crossing over at chiasmata. Microtubules attach to kinetochores and begin moving chromosomes toward the metaphase plate. |
| What is synapsis? | The process by which homologous chromosomes pair up lengthwise during prophase I, forming tetrads. |
| What are tetrads and chiasmata? | Tetrads are the paired homologous chromosomes (each consisting of 4 chromatids) formed during synapsis. Chiasmata are the regions where crossing over occurs, physically linking the pairs. |
| What happens during Metaphase I? (chromosomes/chromatids count) | 46 chromosomes, 92 chromatids. Homologous chromosomes are arranged at the metaphase plate. Independent assortment occurs because the arrangement of homologous chromosomes is random. |
| What happens during Anaphase I? (chromosomes/chromatids count) | 46 chromosomes, 92 chromatids. Homologous chromosomes separate and the spindle apparatus guides them to opposite poles. |
| What happens during Telophase I and cytokinesis? (chromosomes/chromatids count) | 46 chromosomes, 92 chromatids. Homologous chromosomes are separated to each end of the cell. Cytokinesis produces two haploid daughter cells, each containing one chromosome from every homologous pair. At the end, 23 chromosomes, 46 chromatids. |
| What happens during Prophase II? (chromosomes/chromatids count) | 23 chromosomes, 46 chromatids. Spindle apparatus forms and microtubules move chromosomes toward the metaphase plate. |
| What happens during Metaphase II? (chromosomes/chromatids count) | 23 chromosomes, 46 chromatids. Sister chromatids are no longer genetically identical due to crossing over. Chromosomes line up at the metaphase plate. |
| What happens during Anaphase II? (chromosomes/chromatids count) | 46 chromosomes, 46 chromatids. Chromatids separate and move toward opposite ends. Separated chromatids are now considered chromosomes. |
| What happens during Telophase II and cytokinesis? (chromosomes/chromatids count) | 46 chromosomes, 46 chromatids. Nuclei form and chromosomes decondense. Results in four genetically distinct daughter cells total, each with 23 chromosomes and 23 chromatids (1n). |
| What is genetic linkage? | Genes closer together on a chromosome are more likely to be inherited together. Genes physically closer together are less likely to be separated during crossing over. |
| How does meiosis compare to mitosis in chromosome number? | Meiosis reduces chromosome number by half; mitosis keeps it the same. |
| How does meiosis compare to mitosis in number of daughter cells produced? | Meiosis produces 4 haploid (1n) cells (e.g., spermatozoa); mitosis produces 2 diploid (2n) cells. |
| How does meiosis compare to mitosis genetically? | Meiosis produces genetically different cells; mitosis produces genetically identical cells. |
| How does meiosis compare to mitosis in rounds of cell division? | Meiosis undergoes 2 rounds; mitosis undergoes 1 round. |
| How does the division of genetic information differ between meiosis and mitosis? | Meiosis — sister chromatids separate at anaphase II, homologous chromosomes separate at anaphase I. Mitosis — sister chromatids separate during anaphase. |
| Why are sister chromatids in metaphase II no longer genetically identical? | Because crossing over occurred during prophase I, exchanging genetic material between non-sister chromatids of homologous chromosomes. |
| How many daughter cells does mitosis produce, and what are they? | 2 genetically identical diploid (2n) cells, each with 46 chromosomes and 46 chromatids. |
| How many daughter cells does meiosis I produce, and what are they? | 2 haploid daughter cells, each with 46 chromosomes and 92 chromatids (one chromosome from every homologous pair). |
| How many daughter cells does meiosis II produce, and what are they? | 4 genetically distinct haploid (1n) cells total, each with 23 chromosomes and 23 chromatids. |
Created by:
smurtab