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Concepts of Genetics
Seventh Edition
Klug, Cummings, Spencer, Palladino
Chapter 2
Mitosis and Meiosis
Copyright © 2009 Pearson Education, Inc.
Introduction
• Every living thing, except
some viruses, contains
DNA as the genetic material
that houses the information
to control cell structure and
function.
• A molecule of DNA is
organized into units called
genes; the products of gene
expression direct the
metabolic activity of cells.
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Introduction
• DNA is also organized
into chromosomes
which serve as the
vehicles for transmitting
genetic information.
• Chromosomes are only
visible during mitosis
and meiosis. During
interphase DNA is
organized as chromatin.
Copyright © 2009 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc.
Mitosis
• Leads to the
production of two
new cells, each
with the same
number of
chromosomes as
the original parent
cell.
• Occurs in Somatic
(body) cells.
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Meiosis
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• Reduces the genetic
content and the number
of chromosomes precisely
in half. This reduction is
essential if sexual
reproduction is to occur
without doubling the
amount of genetic
information in each
generation.
• Occurs in Gametic/Germ
line (sex) cells.
Copyright © 2009 Pearson Education, Inc.
Figure 2.1
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Figure 2.2
Prokaryote vs. Eukaryote
Prokaryotic Cell
Eukaryotic Cell
Example: Bacteria
E. coli
Example: All Plant and Animal cells
Lacks: A nuclear envelope/nucleus
Contains: nucleus
Lacks: nucleolus and other membranebound organelles
Contains: nucleolus and membranebound organelles
DNA present as: long circular molecule
DNA present as: organized, extensively
coiled structures.
DNA does not: undergo extensive coiling
DNA does: super coil into chromosomes
fro cell division.
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Structure
General Function
Genetic Function
Cell Membrane
Defines and limits cell boundary to
external environment
Offers protection from mutations
Glycocalyx
Provides cell identity markers
Provides genetic identity for
chemical signaling
Nucleus
Houses and protects DNA from external environment
Chromatin
Uncoiled, functioning DNA; cell instructions for work
Chromosomes
Supercoiled/condensed structures that permit equal division of DNA during
Mitosis and Meiosis
Nucleolus
Produces rRNA for use in gene expression (protein production)
Cytoplasm
Houses organelles; location of cell work
Location for gene expression
Endoplasmic
reticulum
(rough)
Fold and process newly made proteins
Translation of RNA to proteins
Mitochondria
Energy for cell work
Energy for cell division and gene
expression
Chloroplast
Traps sun energy to produce glucose
Provides energy for plant cell
division.
Centrioles
Produces spindle fibers for Mitosis and Meiosis
Spindle
Fibers
Important in proper movement/separation of chromosomes during Mitosis and
Copyright © 2009 Pearson Education, Inc.
2.2: Chromosomes Exist in Homologous
Pairs in Diploid Organisms
• Each chromosome contains a
constricted region called the
centromere; this provides a
general appearance of each
chromosome.
• p-arm: “short arm”
• p = petite
• Located above the centromere
• q-arm: “long arm”
• Located below the centromere
Copyright © 2009 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc.
Figure 2.3
Diploid Number (2n)
• Found in Somatic cells; contains the genome
for an organism.
• Homologous chromosomes: each pair of
matching chromosomes with identical size,
shape, and centromere location.
• Contains identical genes.
• Locus: gene location; each chromosome has
several loci along its length.
• In humans, all chromosomes EXCEPT sex
chromosomes (the 23rd pair) are homologous.
• Alleles: alternate forms of a gene; options.
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Term Example
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Karyotype
• Photograph of Mitotic chromosomes to
examine for chromosomal aberrations.
• Sister Chromatids: parallel structures.
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Copyright © 2009 Pearson Education, Inc.
Figure 2.4
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Figure 2-4b
Copyright © 2006 Pearson Prentice Hall, Inc.
Haploid Number (n)
• Equal to ½ of the diploid number.
• Contains the genome of the species.
Copyright © 2009 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc.
Table 2.1