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Mol and Cell Bio
Dr. Andraso's final
| Question | Answer |
|---|---|
| Eukaryotic Chromosomes | When cells get ready to divide, the chromosomes compactg enough to be seen with a light microscope |
| Sister Chromatid/Centromere | Sister Chromatid-are the result of DNA replication followed by condensation of chromosomes ~have identical genetic information Centromere- the narrow "waist" of the duplicated chromosome, where the two chromatids are most closely attached. |
| # of chromosomes in the human body | we have 23 pairs of chromosomes or 46 total chromosomes -autosomes (non sexual)- 22 pairs -sex chromosomes- 1 pair, either XX or XY |
| Ploidy | Diploid (2n)-humans have 23 pairs of chromosomes Haploid (n)- human gametes have 1 member of each pair of chromosomes or 23 total chromosomes |
| Homologous | members of a pair of chromosomes are called this because each chromosome (homologue) is nearly identical in size and genetic composition |
| The Cell Cycle | consists of the Mitotic phase (mitosis and cytokinesis) and Interphase |
| Interphase | -90% of the cell cycle -can be divided into subphases: -G1- first gap -S phase- Synthesis -G2 phase- Second gap -The cell grows during all three phases, but chromosomes are duplicated only during the S phase |
| How does a cell decide to divide? | By external factors: -Evnironmental conditions -Signaling molecules and Internal Factors: -Cell cycle control molecules -Checkpoints |
| Checkpoint Proteins | Cyclins and Cyclin-dependent kinases (cdks) are responsible for advancing a cell through the phases of the cell cycle -Amount of cyclins varies through cycle -Kinases controlling cell cycle must bind to a cyclin to be active |
| 3 critical checkpoints in eukaryotes | G1 checkpoint, G2 checkpoint, and metaphase checkpoint -checkpoint proteins act as sensors to determine if the cell is in proper condition to divide -loss of checkpoint function can lead to mutation and cancer |
| Mitotic Cell Division | -A cell divides to produce 2 new cells genetically identical to the original -Involves mitosis and cytokinesis |
| Functions of Mitotic Cell Division | 1) asexual reproduction 2) growth 3)replacement of cells 4)repair of damaged tissue |
| Prophase of Mitosis | -Chromatids shorten and thicken through condensation -Centrioles continue to move to opposite poles -Mitotic Spindle beings to form between them -Nucleoli begin to diappear |
| Prometaphase of Mitosis | -Nuclear envelope breaks -Astral fibers radiate from the aster -Chromosomes move to the equatorial pleate (metaphase) plate |
| Anaphase of Mitosis | -Sister chromatids separate and begin to move toward opposite poles -Chromatids are now called chromosomes |
| Telophase of Mitosis | -Spindle fibers break down -Cleavage furrow in animals, cell plate in plants -nuclear envelope reforms |
| Mitotic Spindle | an apparatus of microtubules that controls chromosome movement during mitosis |
| Centrosome | During prophase, assembly of spindle microtubules begins in here, the microtubule organizing center -it replactes, forming two that migrate to opposite ends of the cell, as spindle microtubules grow out from them |
| Kinetochore | During prometaphase, some spindle microtubules attch to this and begin to move the chromosomes. |
| Metaphase Plate (Equitorial Plate) | At metaphase, the chromosomes are all lined up at this, the midway point between the spindle's two poles |
| Kinetochore Microtubules | In anaphase, sister chromatids separate and move along these toward opposite ends of the cell -These shorten by depolymerizing at their kinetochore ends |
| Non-kinetochore microtubules (polar microtubules) | -these are at opposite poles and overlap and push against each other, elongating the cell |
| Meiosis | -Is the process by which ploidy is reduced by half -Diploid to haploid (2n to n) -Tetraploid to diploid (4n to 2n) -Octaploid to tetraploid (8n to 4n) |
| Sexual Reproductions | two parents give rise to offspring that have unique combinations of genes inherited from the two parents -Sexual repro= meiosis+fertilization |
| Gametes | sexual cells -are the only haploid cells in animals -fuse to form a diploid zygote that divides by mitosis to develop into a multicellular organism |
| Sporophyte | -The sexual cell in plants and algae -a diploid organism that makes haploid spores by meiosis |
| Gametophyte | Each spore from the meiosis of a sporophyte, grows by mitosis into this organism -This makes haploid gametes by mitosis |
| Zygote | -Single-celled -In most fungi and some protists, the only diploid stage is this -Produces haploid cells by meiosis |
| Meiosis I | -Homologous chromosomes separate -results in two haploid daughter cells with replicated chromosomes (i.e 2 chromatids per chromosome) |
| Meiosis II | -Sister Chromatids separate -results in four haploid daughter cells with unreplicated chromosomes (i.e 1 chromatid per chromosome) |
| Comparison of Mitosis and Meiosis | -Mitosis conserves the number of chromosome sets , producing cell that are genetically identical to the parent cell while Meiosis reduces the number of chromosomes sets from two (diploid), to one (haploid) producing cells that differ genetically from each |
| When does DNA replication happen in mitosis and meiosis | Mitosis=during interphase Meiosis=interphase before meiosis I |
| How many divisions occur in mitosis and meiosis? | Mitosis: one Meiosis: two |
| When does synapsis of homologous chromosomes occur in mitosis and meiosis? | Mitosis: Doesn't occur Meiosis: occurs druing prophase I |
| How many daughter | |
| Metaphase of Mitosis | -Double-stranded chromosomes lie on the equatorial plate. Two sister chromatids are held together by the centromere |
| Prophase of Meiosis I | -Chromosomes begin to coil and condense -centrioles move to the opposirte poles of the nucleus synapsis happens (pairing of homologous pairs of chromosomes) -has a tetrad (two pairs of homologous chromosomes) |
| Metaphase of Meiosis I | -tetrads lie on the equatorial plate -Spindle fibers from one pole attach to the centromere of one homologue while the other one attaches to the other set |
| Aanaphase of Meiosis I | -homologous chromosomes separate from each other and move to opposite poles of the cell -Number of chromosomes has been reduced by one half (N=2) |
| Telophase of Meiosis I | -The two nuclie now fom -cytokinesis 0Each daughter cell produced has half as many chromosomes as the starting cell. |
| What is the difference between Meiosis II and mitosis? | None. |
| Aneuploidy | -Alteration number or particlular chromosomes Types: -Trisomy: normal 2 copies of a chromosome plus a 3rd --> 2n+1 -didnt seperate the homologous pair in meiosis I -Monosomy: missing one normal copy of a chromosome 2n+1 |
| Nondisjunction | -Chromosomes do not sort properly during cell division -During meiosis can produce3 gametes with too many or too few chromosomes -can happen in metaphase of Mei I or Mei II, possible missing spindle fibers |
| Aneuploidy in humans | -5-10% embryos affected -Approx. 50% of all miscarriages are due to alterations in chromosome number -Can survive some abnormalities like trisomies, but no monosomies (except sex chromosomal monosomies) |
| Where can abnormalities happen that are not fatal? | Chromosome 1, 13, 18, 21 and the XY |
| Mutations create different versions of genes called | Alleles |
| Reshuffling | causes genetic variation in alleles |
| Three mechanisms that contribute to genetic variation | -Independent assortment of chromosomes -Crossing over -Random fertilization |
| how many combinations of a gamete are possible | for humans : 23 chromosomes 2 chromatids per chromosome 2^23 8 million! |
| Recombiant chromosomes | -combine genes inherited from each parent |
| Crossing over | -Happens in very early prophase I -homologous portions of two nonsister chromatids trade places |
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haley6719
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