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Concepts of GeneticsSeventh Edition

Klug, Cummings, Spencer, Palladino

Chapter 2

Mitosis and Meiosis

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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.

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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

• 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

Copyright © 2009 Pearson Education, Inc. Figure 2.2

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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 membrane-

bound organelles

Contains: nucleolus and membrane-

bound 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

Meiosis.

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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. Figure 2.3

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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 2-4b Copyright © 2006 Pearson Prentice Hall, Inc.

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Haploid Number (n)

• Equal to ½ of the diploid number.

• Contains the genome of the species.

Copyright © 2009 Pearson Education, Inc.Table 2.1