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31 Cards in this Set
- Front
- Back
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eukaryotic cell cycle ⭐️pic |
-G1➡️S➡️G2➡️M -G1/S/G2 = interphase -no active division -chromosomes are replicated in preparation for mitosis -chromosomes appear as extended filaments and cannot be seen with a light microscope 1. G1 phase: gap 1, growth, prepares for DNA replication 2. S phase: DNA is replicated, chromosomes = two sister chromatids 3. G2 phase: gap 2, prepares for cell division 4. M phase: final cell cycle phase (1/2-2 hours) -G0 = resting phase, cells that are eventually going to die |
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mitosis |
-cell division where single cells reproduce themselves -daughter cells identical to each other and the parent cell -all cells = diploid (2 copies of each chromosome) -four phases: 1. prophase 2. metaphase 3. anaphase 4. telophase -IPMAT: interphase prophase metaphase anaphase telophase |
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mitosis prophase (pic) |
-less than 1/2 of mitosis is spent in prophase 1. centrioles migrate to form poles -poles = axis for chromosomal segregation -chromatin fibers begin to condense ➡️ "hallmark feature of prophase" -threadlike chromosome become visible -double structure with 2 chromatids held together by centromere 2. spindle fibers begin to form -pull chromatids apart to opposite poles |
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mitosis prometaphase (pic) |
-nuclear membrane disappears -spindle fibers make contact with chromosomes -chromosome move to the equatorial plane "metaphase plate", led by centromere |
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mitosis metaphase (pic) |
-chromosomes are fully condensed -alignment on the metaphase plate -centromere is along the plate with chromosome arms extended toward the poles -sister chromatids remain intact but are ready for migration to opposite poles in anaphase -occurs via the spindle fibers attached to the kinetochore |
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kinetochore (pic) |
-protein structure associated with the centromere |
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anaphase (pic) |
-shortest phase of mitosis -sister chromatids disjoin and migrate to opposite ends of the cell -spindle fibers pull the chromatids apart at the centromere -each chromatid is now called "daughter chromosome" -at end of anaphase each pole has identical set of chromosomes (2n) |
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telophase (pic) |
-final stage of mitosis -complete set of chromosomes at each end -cytokinesis: division of cytoplasm into two cells (plants = cell wall develops where metaphase plate was, animals = plasma membrane is constricted/pinched into 2 cells) -chromosomes uncoil into chromatin -PM reforms -2 identical daughter cells with identical copies of the genetic material |
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mitosis vs meiosis (pic) |
-mitosis: daughter cells with same amount of genetic material as paternal - one duplication, one division (diploid ➡️ diploid) -meiosis: daughter cells with half the genetic material as paternal - one duplication, two divisions (diploid ➡️ haploid) |
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meiosis overview |
-two successive nuclear divisions (meiosis I + meiosis II) -produces 4 cells: each with only one member of each pair of pre-meiotic cell chromosomes -"meioum" = "to reduce" (Greek) -homologous chromosomes pair during meiosis to allow for reduction all division - "key feature" -interphase is prior to meiosis just like mitosis (DNA/chromosomes replicate) -stages of meiosis 1. meiosis I: first meiotic division, reductional division -prophase I, metaphase I, anaphase I, telophase I 2. meiosis II: second meiotic division, equational division -prophase II, metaphase II, anaphase II, telophase II |
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meiosis I prophase I (pics) |
-several days 1. leptotene 2. zygotene 3. pachytene 4. diplotene 5. diakinesis -main feature of meiosis -important to understanding how meiosis ⬆️genetic diversity |
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meiosis I prophase I leptotene |
-chromosomes long/threadlike structures -DNA was duplicated during prior interphase -chromosomes condense and become visible |
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meiosis I prophase I zygotene (FIND A PIC) |
-homologous chromosomes pair (synapsis) -synapsis is facilitated by the synaptomenal complex: ribbon that forms between the paired chromosomes -paired homologous = "bivalents" -four chromosomes = "tetrad" - where can see sister chromatids |
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meiosis I prophase I pachytene (pic) |
-synapsis is complete (all paired) -sister chromatids are visible -each homologous pair has 4 chromatids -crossing over occurs (not obvious until next phase): physical exchange of genetic material between chromatids of homologous chromosomes (NOT SISTER CHROMATIDS) -chromosomes become a mosaic of the maternal and paternal homologs -⬆️genetic diversity -chiasma: point of crossing over -genetic recombination |
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meiosis I prophase I diplotene |
-chromosomes get shorter/thicker -homologous chromosomes begin to separate -each chromosome pair had at least one or more chiasma -chiasma = result of breakage and rejoining between nonsister chromatids = point of crossover -crossover become visible ⭐️⭐️⭐️ |
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meiosis I prophase I diakinesis |
-fully condensed chromosomes -homologous chromosomes repel each other, held together by chiasma -nuclear membrane breaks down -spindle fiber formation is initiated |
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meiosis I prophase I overview |
(pic) -leptotene: condense + visible -zygotene: synapsis -pachytene: crossover -diplotene: chiasma crossover = visible -diakinesis: fully condensed, homologs repelling each other, only held together at chiasma |
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meiosis I metaphase I |
-alignment -tetrads move and align on equatorial plane -centromeres of bivalents homologs are positioned toward opposite poles |
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meiosis I anaphase I |
-homologous chromosomes are drawn to opposite poles -homologs disjoin (disjunction occurs) -centromeres do not divide so each chromosome is still 2 sister chromatids -random separation of chromosomes -Mendelian independent assortment |
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meiosis I telophase I |
-chromosomes are at the poles -haploid set at each pole -one homolog from each bivalent at each pole -cytoplasm divides |
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interkinesis |
-period between meiosis I and II -nuclear membrane forms around each set -chromosomes uncoil/decondense and each one still consists of two sister chromatids -(formation of two daughter cells may or may not occur as in mitosis) |
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meiosis I overview (2 pics) |
-metaphase I: some are mosaics, result of crossing over |
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meiosis II overview |
-resembles normal mitosis (separation of sister chromatids) -only one member of a chromosome pair in the nucleus -the chromosome number remains the same in each cell before and after the second division (equational division) -no DNA replication occurs before meiosis II |
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meiosis II phases (pic) |
1. prophase II: chromosomes condense, nuclear envelope breaks down, begin moving toward equatorial plate, spindle fibers reform 2. metaphase II: chromosomes align on equatorial plate 3. anaphase II: centromeres (kinetochores) separate, chromatids disjoin (move to opposite poles), each chromatids is a distinct chromosome 4. telophase II: chromosomes reach the poles, nuclear membranes form around each set of chromosomes, cytokinesis occurs (cytoplasm divides) ➡️four daughter cells ➡️each contains a single (haploid) set of chromosomes that become gametes |
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animal oogenesis (pic) |
-formation of mature egg cells (oocytes = meiocytes) -in a female 3 of the haploid cells made in meiosis contain little cytoplasm and degrade -one cell contains majority of cytoplasm (majority of cytoplasm goes into that cell at each division) and becomes egg (ovum) -polar body at each step, usually just dissolve, don't divide and move forward -females are born with all of the eggs (oocytes) they will ever possess -first division begins in the embryonic ovary: stops in prophase I (suspended in diplotene), resumes prior to ovulation -second division: completed after fertilization -one diploid germ cell ➡️ one product |
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animal spermatogenesis (pic) |
-spermatogenesis: formation of mature sperm cells -all four haploid cells produced during meiosis become functional sperm cells -among the smallest cells in an organisms -consist of a head and tail: head had enzymes to break down the egg's plasma membrane so sperm can enter, tail has mitochondria to provide energy to move sperm -fertilization: occurs with the union of egg and sperm |
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plant spores |
-spores: haploid cells produced in meiosis, divides mitotically to produce a gametophyte -gametophyte: fully developed multicellular haploid organism |
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megasporogenesis (pic) |
-megasporogenesis: development of embryo sac in plants -megaspores: 4 haploid cells produced in meiosis, only one megaphone is carried forward/three degrade -⭐️in both male and female flowers? -mature female gametophyte (embryo sac): nucleus of the surviving megaspores divides mitotically 3 times but does not cytokinese (8 nuclei at end) -3 antipodal cells, 2 polar nuclei, 2 synergids, egg |
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plant microsporogenesis |
-microsporogenesis: pollen grain development -4 haploid cells produced in meiosis are called micro spores (each can become a functional pollen grain) -a microspore nucleus will divide mitotically to form 2 nuclei within the original spore wall 1. tube nucleus: makes pollen tube 2. generative nucleus: divides again producing 2 sperm nuclei ➡️ entire structure (TN + GN) = pollen grain |
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plant fertilization |
-embryo sac with a pollen grain -one sperm nucleus unites with the egg to produce zygote (embryo) -the other sperm nucleus unites with the 2 polar nuclei and becomes the endosperm ➡️ double fertilization -embryo = diploid (egg n + sperm n = 2n) -endosperm = triploid (polar nucleus n + polar nucleus n + sperm n = 3n) |
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plant gamete formation/fertilization cycle overview (pic) |
-megasporogenesis -microsporogenesis |
