Bio Notes 3-4-2016
Bio Notes 3-4-2016 BIOL 1014
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This 3 page Class Notes was uploaded by Crystal Florman on Sunday March 6, 2016. The Class Notes belongs to BIOL 1014 at University of Northern Iowa taught by Dr. Kurt Pontasch in Spring 2016. Since its upload, it has received 25 views. For similar materials see Life: Continuity and Change in Biology at University of Northern Iowa.
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Date Created: 03/06/16
Life: Continuity and Change Lecture Notes 3-4-2016 Differentiation All the cells in our body were formed by cell division- therefore, except for mutations, all cells have the same DNA/ genes All cells are not identical- how can cells with the same genes be so different? o Think of genes as being individual recipes in a cookbook o Although all the information is present in each cell, only parts of that information are expressed in a given cell Differentiation- formation of undifferentiated cells into specific cells (stem cells any type of cell) o Some differentiated cells lose their ability to divide and remain in interphase- Nerve cells o Sometimes these cells undergo mitosis, but not cytokinesis- the cell ends up with many nuclei- muscle cells Abnormal Cell Division All cells do not divide at the same rate Each cells has a regulated division rate o Regulated by DNA Sometimes the regulation of cell division breaks down and the cells begin to divide uncontrollably- too many white blood cells Leukemia o Too many undifferentiated cells in any part of the body is called a tumor Benign tumor- cells do not fragment off and spread to other parts of the body- can become large enough to interfere with nearby tissues Malignant tumor- cells break off from original tumor and spread throughout the body making new tumors- metastasize o Cancer- an abnormal group of cells with the potential to be malignant Meiosis Sexual Reproduction- formation of a new individual by the union of sex cells o Male- sperm o Female- eggs o Gametes- general term for any sex cell Fertilization- the uniting of a sperm and an egg Zygote- formed as a result of fertilization and undergoes mitosis to form the organism Most cells in our body contain two complete sets of chromosomes- diploid (2N) Homologous chromosomes- similar genes throughout their length Male and female gametes contain one set of chromosomes- haploids (1N) o When the two haploid gametes come together during fertilization they form a diploid zygote Meiosis- process of reducing the number of chromosomes from diploid to haploid (2N 1N) o If meiosis did not occur the number of chromosomes would double each generation o Only occurs in specialized organs Animals Gonads- in females the ovaries produce the eggs and the testes produce the sperm in the males Plants In females the ovules produce the eggs and in the males the stamen produces the pollen that contains the sperm Meiosis is divided into two different phases- M1 and M2 o Meiosis I- sometimes called reduction division because the daughter cells end up with half the chromosomes o 4 stages Prophase I- Chromatin coils and thickens Nuclear membrane disintegrates Spindles form Homologous chromosomes come to lie next to each other- synapsis Metaphase I Synapsed homologous chromosomes move to equilateral plane Attached to spindle fiber The way the homologous chromosomes line up is determined by chance Anaphase I Homologous chromosomes separate and move to the poles- diploid to haploid Centromeres holding chromosomes together do not divide Segregation- homologous chromosomes being separated Each pair segregates independently of the other pairs- it’s called independent assortment of chromosomes Telophase I Nuclear membrane reforms Cytokinesis occurs Chromosomes uncoil and become long thin threads Following telophase I the cell enters a period called interkinesis- similar to interphase in mitosis, but no DNA replication occurs Meiosis I- divided homologous chromosome pairs equally between the daughter cells- we have gone from 2N to 1N (46 chromosomes to 23) o Each chromosome is still composed of two chromatin held together by a centromere