Biology 97 Lecture 2 Class Notes
Biology 97 Lecture 2 Class Notes 61860
Irvine Valley College
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This 4 page Class Notes was uploaded by Idda Colcol on Thursday August 25, 2016. The Class Notes belongs to 61860 at Irvine Valley College taught by Amy McWhorter in Fall 2016. Since its upload, it has received 90 views. For similar materials see Genetics and Evolutionary Biology in Biology at Irvine Valley College.
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Date Created: 08/25/16
Bio 97 (#61860): Lecture 2 Class Notes (Slides 22-52) 8/24/2016 I. Cell division plays many important roles in the lives of organisms A. Two methods of reproduction 1. asexual reproduction - offspring inherits genes from single parent and is therefore identical to original cell (parent) 2. sexual reproduction - offspring inherits unique set of genes with variation in traits from two parents and have characteristics similar to both parents II. Prokaryotes reproduce by binary ﬁssion A. Prokaryotes do not undergo mitosis or meiosis but instead undergo reproduction by 1. binary ﬁssion - dividing in half a) replicated circular DNA separates b) 3 stages (1) chromosome duplicates and the copies separate (2) as the cell elongates, the copies continue to move and separate, eventually forming a cluster of cells called a colony (3) the cell is divided into daughter cells by the middle of the cell pinching off III.Eukaryotic cell cycle and mitosis A. Eukaryotic cells are 100x larger and have a lot more DNA B. genes are linear, meaning there is a beginning and end compared to circular genes in prokaryotes IV. Eukaryotic chromosomes A. chromosomes - self-replicating (replicate on their own) that contain linear set of genes in nucleotide sequences 1. visible at division time B. chromatin - a complex of DNA and protein molecules found in nucleus 1. histones - protein molecules that bind to DNA, largely contain amino acids lysine and arginine, foundation for nucleosomes a) responsible for keeping things neat and tidy C. nucleus looks like a cloud, DNA is super thin D. DNA is so long that in order to ﬁt in the cell it needs to be packed in a complex system of coiling and folding 1. some DNA are tightly packed while others are loosely packed depending on whether genes are expressed or not a) Heterochromatin - DNA are tightly packed where genes don’t need to be expressed (1) incapable of being expressed (2) like a closet or drawer, you store clothes you aren’t wearing or using so they are “tightly packed” b) Euchromatin - DNA are loosely packed where genes are expressed (1) as if they are clothes you are wearing at the moment (being expressed), so they are “loosely packed” V. Humans A. somatic cell - cells in an organism that are not gametes 1. soma = body B. karyotype - a visual of the arrangement of chromosomes illustrating their size, number, and shape 1. we use karyotypes to note for any abnormalities in chromosomes 2. the bright colors that illustrate each chromosome are ﬂuorescent strains VI. Homologous Chromosomes A. homologous chromosomes - matching pair of chromosomes that contain same genes but not necessarily same alleles 1. same arrangement, number, and types of chromosomes B. sister chromatid - copy of original chromosome that is bundled with original chromosome by a centromere after DNA replication VII.Ploidy A. Ploidy is deﬁned as how many sets of chromosomes there are B. Diploid (2n) - refers to diploid chromosome number, set of 23 chromosomes from mom, another set of 23 chromosomes from dad C. Haploid (n) - refers to haploid chromosome number, having one set of homologous chromosomes 1. occurs in gametes D. Having extra genes can be deleterious, not a good thing VIII.ell Cycle A. somatic cells divide to form new cells through the cell cycle 1. 2 phases a) Interphase (1) cells spend most of their time in interphase (2) 3 parts: G1, S, G2 (a)G1 (gap phase or growth phase) i) chromosomes are not dividing or duplicating ii) the cell prepares for replication in S phase iii)the critical point for replication occurs in between the G1 and S phases (b)S (synthesis phase) i) cell duplicates to form an identical set of chromosomes called sister chromatids ii) At the end of S phase, there are 46 chromosomes (c)G2 (gap phase or growth phase) i) this part is after chromosomes have been duplicated and before cell division ii) the cell grows, but for a shorter period of time compared to the G1 phase iii)proteins are synthesized b) Mitotic phase (mitosis) (1) cell division IX. Chromosome Duplication A. A cell must duplicate its chromosomes before it can undergo division B. this duplication results in two copies of sister chromatids C. sister chromatids are joined together by chromatids that are later pulled apart to form daughter cells X. Mitosis and Cytokinesis A. Mitosis is nuclear division where the cell divides to form two nuclei and where identical chromosomes are produced B. Cytokinesis is not ofﬁcially part of mitosis but usually accompanies it XI. Mitosis A. 4 phases 1. Prophase, Metaphase, Anaphase, Telophase XII.Prophase A. 3 important things happen 1. chromatin condense into chromosomes 2. nuclear envelope breaks down 3. centrosomes migrate to opposite sides of cell XIII.etaphase A. instantaneous phase B. sister chromatids break apart really quick to line up at plate 1. equivalent forces of microtubules force chromosomes to line up XIV.Anaphase A. sister chromatids migrate to opposite poles B. the cell temporarily becomes tetraploid XV. Telophase A. reverse of prophase 1. returning cell to normal state a) nuclear envelope forms b) sister chromosomes attach at opposite ends of cell c) chromosomes unfold back into chromatin XVI.Cytokinesis A. separate event not necessary for mitosis to be complete B. cytoplasm divides C. cytokinesis different in animal and plant cels XVII.Cytokinesis - Animals Cells A. cleavage furrow forms in a cell to form daughter cells XVIII.Cytokinesis - Plant Cells A. In plant cells, there is a presence of cell wall 1. Golgi apparatus sends cell wall material in vesicles (like cell plate) to form a new cell wall that divides the cell into daughter cells XIX.Cell Division: Meiosis A. reduction division B. end up with haploid set C. having extra copy of chromosomes is deleterious XX. Gametes and the Life Cycle of a Sexual Organism A. only sex cells can go through meiosis XXI.Cell Division: Meiosis A. similar mechanisms to mitosis in how chromosomes are manipulated B. different in the presence of roman numerals 1. meiosis has two nuclear divisions called meiosis I and meiosis II XXII.Overview of Meiosis A. in meiosis I, they are haploid but not gametes B. in meiosis II, ploidy doesn’t change XXIII.Interphase A. chromosomes duplicate XXIV. Meiosis I A. Prophase I - homologous chromosomes synapse together and ﬁnd each other B. Metaphase I - tetrad chromosomes line up C. Anaphase I - no centromeres are broken apart D. Telophase - I restore cell, depends on speed of meiosis XXV. Meiosis II A. Prophase II - 23 chromosomes, each chromosome has sister chromatin B. Metaphase II - no more pairs, each individual chromosome lines up C. Anaphase II - immediately occurs, sister chromatids pull apart, daughters migrate, centromeres separate D. Telophase I-I each daughter chromosome gets own nuclear envelope 1. 4 haploid gametes are produced XXVI. Review Comparing Mitosis and Meiosis A. Meiosis II is similar to mitosis except haploid XXVII.Spermatogenesis vs Oogenesis A. in seminiferous tubule cells tend to be large toward the along perimeter, but get smaller toward the center B. volume decreases as it divides C. After meiosis II and once the spermatids have formed, further maturation occurs, growing them into spermatozoa
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