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Ch. 8
Cell Reproduction
Ch 8.1 Chromosomes
How is DNA organized?
 Usually in a cell, DNA is wrapped
histone proteins in long
around ________
strands called chromatin.
 During cell division, the chromatin
condenses into chromosomes.
__________
 The chromosome is made of two
identical DNA structures, called
chromatids, that are joined
together at the _____________.
centromere
Chromatin and Condensed
Chromosome Structure
chromatid
nucleus
centromere
chromosome
chromatin
DNA
helix
histones
Each
species has a specific
number of chromosomes.
_______
Each different
chromosome contains
information for different
traits
________.
Types of Chromosomes
Sex chromosomes: In humans,
X and __,
Y
chromosome __
determine the sex of a person.
–Females have two X, and
males have X and Y.
All other chromosomes are
autosomes
called _____________.
How many chromosomes are in
a cell?
Most
human cells normally
two sets of each
contain ____
chromosome.
diploid cells
These are called _______
and is abbreviated as ____.
2n
Reproductive
cells, sperm and
haploid
egg cells, are _______.
one
Haploid cells contain only ___
set of chromosomes. This is
n .
abbreviated as ___
Karyotype
 An
organized profile of an organism’s
complete set of chromosomes.
 Scientist pair together homologous
chromosomes based on their size,
banding pattern, and position of their
centromere.
 Then they arrange them by size from
largest to smallest.
Human male karyotype
Cell Division
Asexual vs. Sexual
Reproduction
Asexual Reproduction
Requires
only one parent.
Resulting offspring are
genetically identical.
The only source of genetic
variation comes from
mutations.
Budding
Parent produces an
outgrowth that pinches
off, forming a new
organism
Occurs in yeast, hydra,
sponges.
http://www.waycross.edu/faculty/bmajdi/hydra%20budding.jpg
Spore formation
Single
or multi-celled
spores are produced and
grow into a new
organism.
Occurs in algae, fungi,
protists, and plants
Binary Fission
DNA
replicates and one
cell divides into two
Occurs in bacteria,
protozoa, and algae.
Sexual reproduction
Requires
two gametes (sex
cells) : egg and sperm.
The egg and sperm join to
form an entirely new organism
The offspring is genetically
different from the parent
organism
Why do cells reproduce?
Produce
more offspring
(new organisms).
Organism needs to grow
or repair
Prokaryotes
Prokaryotic
cells divide by
binary fission
________
___________.
They have circular
chromosomes without any
proteins and cell division
occurs very quickly.
Eukaryotes
 Eukaryotes
divide by mitosis
 Cells spend only a small
percentage of their time dividing.
 The set of events in the life of a
cell is called the cell cycle.
 A cell spends most of its life in
interphase.
G1 Phase
Cell
size
grows to mature
S Phase
DNA
replicates.
G2
Cell
grows and prepares
to divide.
What is cancer?
 Cancer
occurs when cells do not
stop growing.
 Healthy cells regulate when and
how often they continue in the
cell cycle.
 Cancer cells continuously go
through the cell cycle without
stopping, which leads to a tumor.