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Sept14Lec_part2 - continued[...

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9/14/06 continued [Start of Prelim 2 material] Transcription of Dr. Winkler’s Lecture Start of Material for Prelim # 2 Reproduction & Inheritance: (ppt) ‘Cell Theory’ 1. all living things are made of one or more cells 2. cells are the basic units of life and all the chemical reactions of life occur in cells 3. all cells arise from preexisting cells (ppt) Prokaryotic cell division / cell membrane & cell wall present / binary fission [form of mitotic division] used for reproduction i.nucleus NOT present. Only one chromosome present (ppt) Eukayotic Cell Division [photo summary of cell life-cycle w/regards to DNA] / why have chromosomes at all? / When not dividing, cells don’t package their DNA into chromosomes. / When not dividing, eukaryotic cells don’t package their DNA into chromosomes / Replication (copying DAN) occurs before DNA is wound into chromosomes. (ppt) Shows Chromatin fibers (DNA) coiled into chromosome package when preparing to divide during Mitosis. NOTE: Following DNA replication you now have 2 Sister Chromatids making up the replicated chromosome. (ppt) Homologous pair of chromosomes: NOTE: each replicated chromosome is composed of 2 sister chromatids. / Matching banding patterns [location (loci) of specific genes—we will see later that the different expressions for genes (Dominant vs Recessive) are known as Alleles (alleles are each found at specific loci on specific chromosomes). Scientists use loci to match up homologous pairs of chromosomes. ppt Clicker Quiz Question : “For what pairs of chromosomes does this matching of homologous portions Not work?’ Answer: C. Heterogametic sex (X & Y) = male because males receive one X & one Y sex chromosome. 1
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9/14/06 continued [Start of Prelim 2 material] Transcription of Dr. Winkler’s Lecture (ppt) Cell Cycle – the amount of time spent in each stage of the cell cycle is biochemically controlled There are 4 distinct phases that make up the cell cycle. Three are growth phases and are collectively called Interphase ; the fourth is a period of division, therefore, referred to as M Phase. During interphase , cells typically double in size. The first part of interphase is called G 1 (Gap 1). This is a period marks a maintenance of basic cell activities and takes anywhere from 1 hour to several days depending on the cell type. This is followed by the S phase (synthesis); during this period, which typically lasts 9 hours, DNA is replicated ; this means that a copy of the DNA is made. The last stage of interphase is called G 2 (Gap 2). Here, the cell prepares to divide; certain proteins, called spindle proteins, necessary for cell division are made at this time. G2 takes about 3 hours to complete. Additionally, organelles such as mitochondria, plastids, and ribosomes double in number. After interphase is the M phase. Two critical events occur at this time. The first is mitosis , which is the division of the nuclear material. During mitosis, 2 sets of chromosomes are distributed to opposite ends of the cell and two daughter nuclei form. The other event, which happens near the end of mitosis, is cytokinesis .
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