chapter 12 and 13 notes
chapter 12 and 13 notes BIOL 1020
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This 6 page Class Notes was uploaded by Kendall Mansfield on Friday October 23, 2015. The Class Notes belongs to BIOL 1020 at Auburn University taught by Min Zhong in Fall 2015. Since its upload, it has received 12 views.
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Date Created: 10/23/15
Biology Test 3 Chapters 12 and 13 Intracellular activity between one cell division to the next 0 Cell Growth Process by which a parent cell divides into two or more daughter cells cell splits into two nearly equal halves period from the start of one cell division to the start of the next cell division asexual reproduction sexual reproduction the genetic code sugar base phosphate chain of nucleotides double helix with hydrogen bonds between strands combination of DNA and protein molecules less OOOO condensed formed when chromatin coils up when it is about to divide more condensed middle region where two sister chromatids come in contact 0 mprior to mitosis by DNA duplication 0 pairs during meiosis with genes for the same biological features one from mom and one from dad varies widely but is usually 820 hours I Most cells usually never die and they then enter GO chromosomes duplicate gap recovery DNA synthesis to form sister chromatids gap prepare chromosomes condensed centrioles OOOO replicate the mitotic cytokinesis phasewhen cell division occurs I Nuclear Division I Cytoplasmic Division p prepare 0 Chromosomes condense o Mitotic spindle forms I organizes between the two poles of the cell Each pole has a microtubule organizing center MTOC In animals and some other eukaryotes centrioles are found in the MTOC Plants do not have centrioles Nuclear envelope dissolves Chromosomes are captured by the spindle 0 Short microtubules extended from centrosomes mmiddle o Spindle microtubules pull the chromosomes to align them at the center of a the cell 0 Metaphase plate imaginary plane through the center of the cell where the chromosomes align aapart 0 Removal of cohesion proteins causes the centromeres to separate 0 Microtubules pull the sister chromatids toward the poles 0 Cell elongates 0 Sister chromatids separate ttwo cells Mitotic Spindle breaks down Two daughter cells nuclear envelopes form Chromosomes begin to uncoil Nucleolus reappears in each new nucleus Cytokinesis occurs 0 O O O O o Cytoplasmic Division I late anaphase to end of telophase 0 Two mechanisms 0 I Golgi vesicles line up and fuse I Splits the cell in two I Microfilament actin ring contracts I This process pinches the cell apart 0 1 parent cell 9 2 identical daughter cells 0 Chromosome number remains the same from one generation to the next Plant Vs Animal Cells absent present cell plate cleavage furrow three checkpoints in G1 G2 and mitosis Goahead or stop signal 0 Cyclins and Cyclindependent protein 0 kinases Cdks I Protein kinases phosphorylate proteins to activate or inactivate them 5 divide excessively and can invade other tissues and displaces normal cells abnormal mass of cells tumors do not spread cancerous these tumors can spread growth of cancer cells beyond the original site cancer cells may travel through the circulatory system high energy radiation is used to destroy cells that are dividing targets cancer cells but can destroy normal cells drugs that disrupt cell division Surgery offspring s genetically identical to the parent cells clones Mitotic cell division Split bud or fragment Rapid and efficient Gametes fuse to form a single cell called a zygote Meiosis The offspring are not genetically identical to their parents Genetic recombination A set of chromosomes n has one member for each homologous pair A diploid cell has two complete sets 2n A haploid call has one set n Sometimes cells have extra sets 3n or more and are polyploid 0 common in plants rare and usually fatal in animals Eukaryotic reproductive cells eggs and sperms Meiosis reduces chromosome number Consists of one round of DNA replication followed by two rounds of nuclear divisions These events occur in two stages 0 Meiosis I o Meiosis II o I synapsis I tetrad o I Exchange of genetic material I Cause genetic variation the site of crossing over o Homologous chromosome pairs randomly line up 2abreast I Line up in different ways causing randomly genetic variation 0 Homologous chromosome pairs separate and move to opposite 1 Spindle microtubules disappear 2 Cytokinesis occurs 3 Nuclear envelopes may reappear 4 Chromosomes usually remain condensed 0 Between meiosis I and meiosis II o Varies in length and distinctiveness o Interkinesis differs from interphase because there is no SPhase DNA replication 0 Typically interkinesis is brief some cells skip it altogether o Spindle microtubules reform and capture duplicated chromosomes 0 Duplicated chromosomes line up singly perpendicular to the spindle 0 Sister chromatids separate 0 Cytokinesis occurs 0 Spindle microtubules disappear 0 Nuclear membranes reform o Chromosomes relax The phases of meiosis have the same names as the equivalent phases in mitosis followed by I or II to distinguish the two nuclear divisions that occur in meiosis Crossing over homologous chromosomes separate sister chromatids separate Fertilization combines two chromosome sets to produce diploid 2n zygotes Mitosis is one round of DNA duplication one round of division and results in two diploid daughter cells Meiosis is one round of DNA duplication two rounds of division and results in four haploid daughter cells Occurs during interphase before mitosis begins Occurs during interphase before meiosis I begins one including prophase metaphase anaphase and telophase Two each including prophase metaphase anaphase and telophase does not occur Occurs during prophase I along with crossing over between nonsister chromatids resulting chiasmata hold pairs to ether due to sister chromatid cohesion o i two each diploid 2n and genetically identical to the parent cell 0 Four each haploid n containing half as many chromosomes as the parent cell genetically different from the parent cell and from each other Enables multicellular adult to arise from a zygote produces cells for growth repair and in some species asexual reproduction o Produces gametes reduces number of chromosomes by half and introduces genetic variability among the gametes chromosomes physically connect and exchange genetic information 0 At the metaphase plate there are paired homologous chromosomes tetrads instead of individual replicated chromosomes 0 At anaphase I it is homologous chromosomes instead of sister chromatids that separate o Randomized line up and separation of homologous chromosomes in Meiotic Metaphase I and Anaphase I increase variation 0 The number of possible combinations is 2quotn where n number of homologous pairs 0 So in humans possible combinations in one gamete 2quot23 or about 8 million 0 Crossing Over in Meiotic Prophase I creates chromosomes with new allele combinations 0 Fusion of gametes from two individuals further increases possible 2n combinations 0 Gametes from two humans could produce about 64 trillion different combinations 0 Crossing over adds even more variation 0 Each zygote has a unique genetic identity
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