BIOL 1000 Lecture Notes - Lecture 9: Prophase, G0 Phase, Microtubule
7/2/18
BIOL 1000- MITOSIS AND MEIOSIS
•There are 23 chromosomes from mother and 23 chromosomes from father.
•There are 2 cell types based on chromosome contents: A) Gametes: in which there are 23
dif-
ferent chromosomes that are haploid (n) and include ova (eggs) and sperm. B) Somatic Cells:
which include all cells of the body except cells undergoing or resulting from meiosis; like mus-
cle and nerve cells.
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7/2/18
•There are 46 chromosomes which are diploid (2n); 23 homologous pairs.
•Homologous Chromosomes: a chromosome pair (1 from each parent) that are identical in
length, centromere position and have genes for the same trait like eye colour in the same loca-
tion or locus.
•Gene: it is the unit of heredity and is the region of DNA which contains information for syn-
thesis of proteins, BUT they may have different versions of that trait; like blue eyes (chromo-
some from father) and brown eyes (chromosomes from mother).
•Each somatic cell contains 23 different chromosome pairs. 23 chromosomes form mother
(ovum) which are paired with 23 chromosomes from father (sperm) and that equals 46 chro-
mosomes which are diploid (2n somatic cell).
•The chromosome pairs are numbered from 1-23 and the first 22 pairs are autosomal chromo-
somes or autosomes that contain genes for somatic characteristics like hair and eye colour
and height. The 23rd chromosome contains genes that determine the sex of the child; like
XY from father and XX from mother.
•The somatic ‘parent’ cell (2n) and the genetically identical somatic ‘daughter’ cells (2n). There
are 2 stages to it: Interphase and Mitotic or the cell division phase.
1.1 INTERPHASE: (G1, S AND G2 PHASE):
•Chromosomes present as chromatin. There is normal cellular metabolic activities occurring
like protein synthesis.
•The phases are: A) G1 PHASE: helps in growth and metabolism. At the end of G1 phase the
centromeres replicates.
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•In some cells that do not divide again once mature i.e. they remain in G1 phase in these cells it
is termed as G0 phase; like nerve and some muscle cells.
•B) S PHASE: the chromosomes replicate, but are still present as chromatin which are not indi-
vidually visible. They always occur before the mitotic division. They replicate as ‘sister chro-
matids’ which are attached to each other at an area of DNA called the ‘centromere’. The kine-
tochore proteins (produced during S phase) attach to each centromere to form the kinetochore
(protein and DNA complex).
•A kinetochore is the site of attachment of spindle micro tubules.
• G2 PHASE: it helps in growth, metabolism; the production of enzymes and other proteins
needed for cell division.
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Document Summary
Biol 1000- mitosis and meiosis: there are 23 chromosomes from mother and 23 chromosomes from father, there are 2 cell types based on chromosome contents: A) gametes: in which there are 23 ferent chromosomes that are haploid (n) and include ova (eggs) and sperm. B) somatic cells: which include all cells of the body except cells undergoing or resulting from meiosis; like mus- dif- cle and nerve cells: there are 46 chromosomes which are diploid (2n); 23 homologous pairs. The 23rd chromosome contains genes that determine the sex of the child; like. Xy from father and xx from mother: the somatic parent" cell (2n) and the genetically identical somatic daughter" cells (2n). There are 2 stages to it: interphase and mitotic or the cell division phase. 1. 1 interphase: (g1, s and g2 phase): chromosomes present as chromatin. There is normal cellular metabolic activities occurring like protein synthesis: the phases are: a) g1 phase: helps in growth and metabolism.