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27 Cards in this Set
- Front
- Back
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Mitosis
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theprocess by which millions of cells are made every second in in an animal’sbody, new skin cells, new blood cells, new bone cells etc. In plants, mitosis occurs to increase primarygrowth in shoots and roots and secondary growth in woody plants.
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SisterChromatids.
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Beforemitosis, the DNA is replicated forming chromatids. The two identical chromatids (the original + the copy) will join together;
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The sister chromatids are attached at the _______? |
Centromere |
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Chromosomes
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havehundreds of genes on each one. Humansare 2n=46. We are diploid (2n) organismswhich means we are products of 2 haploid (1n) nuclei. |
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Humans have how many.... Chromosomes? Homologous chromosomes? Genes on the chromosomes? |
46 23 20,000 *Note: Of those 46 Chromosomes; 44 (22 pairs) are autosomes and 1pair are sex chromosomes. |
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CellCycle.
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. G1 (Growth 1, also called Gap 1), S is the synthesis phase when DNAreplicates and G2( growth 2 or Gap 2) is when the DNA condenses. G1, S, and G2=Interphase of the cell cycle. 90% ofa cell’s cycle is spent in interphase. S phase-DNAreplicates-S stands for synthesis of new DNA.Sister Chromatidsform.
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Mitosis |
Cells divide into 2 daughter cells withidentical chromosomes and genes. The 2daughter cells are genetically identical to the parent cell that divided.
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5 phases of mitosis
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1. Prophase 2. Prometaphase 3. Metaphase 4. Anaphase 5. Telophase |
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Prophase |
1. Sister chromatids condense so that they are visible
2. Centrioles migrate to thepoles of the animal cell. 3. The nucleolus and nucleusbegin to fragment |
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Prometaphase |
1. Centrosomes (microtubuleorganizing centers from the centrioles) form and the spindle of microtubulesforms attaches to the sister chromatids at the centromere. The attachment point of the microtubules onthe sister chromatids is called the Kinetochore. 2. Nucleolus and NuclearEnvelope disappear |
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Metaphase |
Sister chromatids line up across the equator ofthe cell on the metaphase plate. |
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Anaphase |
Sister chromatids separate into individual chromosomes during Anaphase (they are no longer sister chromatids). The spindle pulls them towards the poles (each end) of the cell. |
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Telophase |
The nucleus and nucleolus reforms, the spindledisappears, and cytokinesis occurs to form 2 daughter cells.
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Cytokinesis |
the separation of cytoplasm to form 2 daughtercells. Inanimals cells a cleavage furrow is formed during cytokinesis, but in plantcells a cell plate from vesicles that carry cellulose fusing together. This forms the new cell wall in plants.
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G1 Checkpoint |
This checkpoint determines whether cells enter G0 stage and stop mitosis. Most of your cells are in G0. Mature muscle and neurons are in G0 as is mature liver cells etc. |
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G2 Checkpoint |
Cyclins that control mitosis degenerate at the end of Mitosis. They star to be produced during S phase and increase into G2. There are enzymes called Cylcin Dependent Kinases (CDK). |
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M Checkpoint |
Sister chromatids are retained in Metaphase until every microtubule is attached to one of the sister chromatids, then the cell can proceed to Anaphase.
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Cancer
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mitosis gone wild. Cancer arises from a single cell, when mutations occur in Protooncogenes and Tumor suppressor Genes. This causes cancer.
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Benign tumors
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normallooking cells justgo through mitosis a little faster than normal cells-noninvasive to othertissues.
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Malignant tumors
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cells do not look normal in biopsy-cells are constantly going through mitosis-No G1 or G2 phases of the cell cycle. These cells just replicate their DNA and start mitosis. These tumor cells are invasive into other tissues and will break off into the lymphatic system or the circulatory system-metastases.
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Proto-oncogenes
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genes that code for normal growth factors (cell cycle control proteins). They may become oncogenes (cancerous) when they turn on and stay turned on. Tumor suppressor genes become oncogenes when they mutate and stay turned off, so they cannot prevent tumor formation.
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Cancer caused by 4 major factors
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1. Viruses : insert their DNA into host DNA and theproto-oncogenes becomes an oncogene
2. Chemicals- chemicals can cause mutations in the genes that make the cell cycle control proteins. 3. Radiation-(from sunlight UV rays; x rays; radon) cause mutations in genes that make the cell cycle control proteins. 4. Heredity—Predisposition due to certain inherited proto-oncogenesIncrease risk of cancer. |
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Meiosis =Reduction Division
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A diploid cell divides by meiosis to make 4 haploid cells (half the number of chromosomes).Diploid cell 2n= 50 will form haploid cells n=25.
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Homologous chromosomes
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are the pairs of chromosomes in diploid organisms. We get 23 from the egg nucleus (1n) and 23 from the sperm nucleus (1n) that code for the same genes-Karyotype Because we have pairs of chromosomes we are diploid (2n) organisms. 2n = 46 chromosomes or 23 pairs of homologous chromosomes.
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Gametes
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are sex cells (eggs that are made in the ovaries) and sperm that are made in the testes. (In plants sperm is found in pollen, and eggs in ovaries). Gametes are haploid sex cells.
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Process of Meiosis
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diploid cells go through 2 rounds of cell division (meiosis I and meiosis II) and only replicate their chromosomes once in S phase of the cell cycle. The diploid cell will go through 2 rounds of division to make 4 haploid (n) cells. For humans: haploid eggs and sperm, each with 23 chromosomes. 4 x 23 = 92
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Meiosis I
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consists of Prophase I, Metaphase I, Anaphase I, and Telophase ITetrads are homologous pairs of chromosomes consisting of maternal sister chromatids and paternal sister chromatids.
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