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Northeastern University - BIOL 2301 - Class Notes - Week 2

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Northeastern University - BIOL 2301 - Class Notes - Week 2

School: Northeastern University
Department: Engineering
Course: BIOL2301
Professor: Brian Conlon
Term: Fall 2017
Tags: Genetics
Name: Chapter 3
Description: Meiosis/Mitosis and Chromosomes
Uploaded: 01/22/2018
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background image Chapter 3  Discovery of Chromosomes o Chromosomes and mitosis were discovered by Walther  Flemming in the 1880s Flemming didn’t know Darwin’s results o It took several decades before the connection between  chromosome segregation and assortment of traits was 
appreciated
Somatic Cells o Somatic cells are cells of the body (basically everything  except gametes) o Diploid means there are two copies of each chromosome in each diploid cell  o Human somatic cells contain 23 pairs of chromosomes for  a total of 46 Gametes o Gametes are reproductive cells Ex: Sperm, oocytes, and pollen o Haploid means there is one copy of each chromosome in  each haploid cell o Haploid gametes unite in fertilization to produce a diploid  embryo  Mitosis  o Mitosis is a process of chromosome segregation and cell  division that results in two genetically identical diploid 
daughter cells 
Cell Cycle 
background image Chromosomes during the cycle    Nomenclature in Chromosome Replication  Interphase (G1, S, G2) o Everything except mitosis
o Chromosome are not lined up and are not as condescend
Stages of Mitosis   o Prophase  Chromosomes condense  Chromatids are attached to each other at the 
centromere
o Metaphase Mitotic spindle forms and attaches to the
chromatids near the centromere at a structure called 
a kinetochore 
Chromosomes move to the metaphase plate  Proper chromosome alignment is essential  o Anaphase Centromeres divide  Sister chromatids separate and move to opposite 
poles 
o Telophase and Cytokinesis  Nuclear membrane forms around each compact 
group of chromosomes 
Homologous 
background image Chromosomes become de-condensed  In cytokinesis, the cell divides to form two daughter 
cells
o Mitosis vs Meiosis Mitosis produces duplicate somatic cells Meiosis produces haploid germ cells Meiosis  o Meiosis is a process of chromosome segregation and cell  division that results in four haploid daughter cells  This requires two divisions, meiosis I and meiosis II, 
and is known as reductional division
o Meiosis I  One cell duplicates its DNA, then divides, but the 
chromosomes are handles differently from mitosis 
Prophase I – chromosomes condense, pair, and cross 
over
Synapsis – pairing of homologous 
chromosomes 
Chiasmata – connections between homologous 
chromosomes 
o Results from physical exchange of DNA  between chromatids of homologous 
chromosomes 
o Two important purposes of chiasmata Stick the homologous 
chromosomes together so the 
chromosomes can align correctly at
the metaphase plate in Metaphase 
Exchange genetic information 
between homologs to increase 
genetic diversity 
Crossing over (or recombination) is a genetic 
exchange between homologous chromosomes 
Metaphase I – bivalents align at the center  Bivalents are a pair of homologous 
chromosomes (each consisting of two 
chromatids) associated with meiosis I 
Alignment is random  o Independent assortment of genes on  separate chromosomes  Anaphase I – chromosomes separate to the poles  Telophase I – cells get set up for Meiosis II  During telophase, the spindle breaks down 

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School: Northeastern University
Department: Engineering
Course: BIOL2301
Professor: Brian Conlon
Term: Fall 2017
Tags: Genetics
Name: Chapter 3
Description: Meiosis/Mitosis and Chromosomes
Uploaded: 01/22/2018
11 Pages 37 Views 29 Unlocks
  • Better Grades Guarantee
  • 24/7 Homework help
  • Notes, Study Guides, Flashcards + More!
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