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asexual reproduction production of offspring by a single parent sexual reproduction sperm & egg carry one set of genetic information (increases genetic variation) cells ____ are the basic units of life. cells All living things are composed of ___. binary fission the process in which prokaryotes (bacteria) reproduce DNA Genes are carried on circular ___. chromatin Chromosomes are composed of ____ (combo of DNA and histone proteins). centromere sister chromatids are held together by a ____, a protein disk). G1 phase period before DNA synthesis begins; refers to the gap between cell division and DNA synthesis; time when the cell increases its supply of proteins, organelles, & grows in size. S phase phase where DNA synthesis (replication) occurs; at the beginning, each chromosome is single and at the end there are two sister chromatids. mitosis nucleus and its contents divide and are evenly distributed to form two daughter nuclei. Chromosomes are visible. cytokinesis usually begins before mitosis is complete; division of cytoplasm prophase chromatin fibers condense forming discrete chromosomes; nucleoli disappear; spindle fibers begin to form from the centrosomes; nuclear envelop fragments metaphase spindle fibers are fully formed; chromosomes convene in middle of cell; centromeres are lined up at the metaphase plate; microtubules attach to the kinetochore on the sister chromatids anaphase two centromeres of each chromosome come apart; chromosomes move to opposite poles of the cell; microtubules attached to kinetochores shorten; poles move farther apart; complete when chromosomes have reached the two poles of the cell. telophase reverse of prophase; daughter nuclei appear at two poles; chromosomes uncoil and nucleoli reappear; spindle fibers disapear ;cytokinesis occurs. cleavage furrow found in animals; begins as a ring of microfilaments that eventually pinches the cell in two. cell plate found in plants; vesicles fuse with the plate carrying cell wall material (cellulose). skin ___ cells divide frequently muscle/nerve these cells never divide. anchorage dependence keeps cells that have become separated from their normal surroundings from dividing inappropriately density-dependent inhibition cell division slows as the cell population becomes denser growth factor proteins secreted by certain body cells that stimulates cells that trigger and coordinate major events in the cell cycle cell cycle control system cyclically operating sets of proteins in the cell that trigger and coordinate major events in the cell cycle benign tumors abnormal mass of normal cells malignant tumors mass of cancer cells metastasis spread of cancer cells beyond their original site carcinomas originate in external and internal coverings of the body sarcomas tissues that support the body (bond & muscle) leukemias cancer of blood-forming tissues radiation treatment that disrupts cell division chemotherapy drugs that disrupt cell division autosomes the first 22 pairs of homologous chromosomes found in males & females sex chromosomes the 23rd pair of chromosomes (male = XY, female XX) gametes ___ have a single set of chromosomes diploid cells cells who's nuclei contain two sets of chromosomes haploid cells cell with a single chromosome set (ex. gametes) Fertilization fusion of the egg and sperm zygote first cell of a new individual meiosis gametes are made through the process of ____. meiosis starts with diploid and ends with haploid mitosis starts with haploid and ends with diploid prophase I occupies over 90% of the time required for meiosis; chromosomes condense & become visable; synapses occur; crossing-over occurs; centrosomes move to opposite sides; nuclear envelope fragments; chromosome tetrads move toward center of cell prophase I crossing-over occurs during this phase metaphase I chromosome tetrads are aligned on metaphase plate; sister chromatids are still attached to each other by the centromere; spindle fibers are attached to kinetochores at the centromeres. anaphase I homologous tetrads separate and move toward opposite poles of the cell; law of independent assortment occurs anaphase I Law of Independent Assortment occurs during this phase telophase I chromosomes arrive at the poles of each cell; each pole has a haploid set of chromosomes; cytokinesis occurs DO NOT Chromosomes do/do not duplicate prior to meiosis II. Anaphase II Law of segregation occurs during this phase both both/which: chromosomes replicate only once both both/which: the steps of mitosis & meiosis II are similar Meiosis both/which: entails two nuclear divisions forming 4 haploid, non-identical cells; crossing over occurs mitosis both/which: one division of the nucleus; produce two identical offspring law of independent assortment occurs during Anaphase I; states that the movement of homologous chromosomes to opposite poles is random law of segregation occurs during Anaphase II; states that the movement of sister chromatids to opposite poles is random chaisma sites of crossing-over crossing over occurs during synapses at a chaisma alleles different versions of a gene Karyotype orderly display of magnified images of the individual's chromosomes metaphase what phase is a karyotype taken during? Nondisjunction members of a chromosome pair fail to separate; may occur in any anaphase step inversion segment is flipped around deletion piece of chromosome is missing duplication piece of chromosome is added back on to part where cross overs occupied translocation piece attaches to a non-homologous chromosome synapsis when two homo chromosomes come together haploid in Meiosis, in Telophase I, the cells are still ___. centromere protein disk that holds sister chromatids together somatic a gamete has half as many DNA as a __ cell animals centrioles are in __ only microtubules spindle fibers are made from microfilaments ___ form the cleavage furrow G0 Cells that don't divide go to this step