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Mitosis and the Cell Cycle
Interphase and the mitotic phase
alternate in the Cell Cycle.
Cytokinesis
Meiosis
Fig. 13-3
APPLICATION
TECHNIQUE
5 µm
Pair of homologous
replicated chromosomes
Centromere
Sister
chromatids
Metaphase
chromosome
Fig. 13-4
Key
2n = 6
Maternal set of
chromosomes (n = 3)
Paternal set of
chromosomes (n = 3)
Two sister chromatids
of one replicated
chromosome
Two nonsister
chromatids in a homologous pair
Centromere
Pair of homologous
chromosomes
(one from each set)
Fig. 13-5
Key
Haploid gametes (n = 23)
Haploid (n)
Diploid (2n)
Egg (n)
Sperm (n)
MEIOSIS
Ovary
FERTILIZATION
Testis
Diploid
zygote
(2n = 46)
Mitosis and
development
Multicellular diploid
adults (2n = 46)
Fig. 13-6a
Key
Haploid (n)
Diploid (2n))
n
Gametes
n
n
MEIOSIS
FERTILIZATION
Zygote
2n
Diploid
multicellular
organism
(a) Animals
Mitosis
2n
Fig. 13-6b
Key
Haploid (n)
Diploid (2n)
Mitosis
n
Haploid multicellular organism
(gametophyte)
Mitosis
n
n
n
n
Spores
Gametes
MEIOSIS
FERTILIZATION
2n
Diploid
multicellular
organism
(sporophyte))
2n
Mitosis
(b) Plants and some algae
Zygote
Fig. 13-6c
Key
Haploid (n)
Haploid unicellular or
multicellular organism
Diploid (2n)
Mitosis
n
Mitosis
n
n
n
Gametes
MEIOSIS
FERTILIZATION
2n
Zygote
(c) Most fungi and some protists
n
Fig. 13-7-3
Interphase
Homologous pair of chromosomes
in diploid parent cell
Chromosomes
replicate
Homologous pair of replicated chromosomes
Sister
chromatids
Diploid cell with
replicated
chromosomes
Meiosis I
1 Homologous
schromosomes
separate chromosome
Haploid cells with
replicated chromosomes
Meiosis II
2 Sister chromatids
separate
Haploid cells with unreplicated chromosomes
Fig. 13-8a
Prophase I
Metaphase I
Centrosome
(with centriole pair)
Sister
chromatids
Chiasmata
Spindle
Centromere
(with kinetochore)
Sister chromatids
remain attached
Metaphase
plate
Homologous
chromosomes
separate
Homologous
chromosomes
Fragments
of nuclear
envelope
Telophase I and
Cytokinesis
Anaphase I
Microtubule
attached to
kinetochore
Cleavage
furrow
Fig. 13-8
Metaphase I
Prophase I
Centrosome
(with centriole pair)
Sister
chromatids
Chiasmata
Spindle
Centromere
(with kinetochore)
Prophase II
Metaphase II
Anaphase II
Telophase II and
Cytokinesis
Sister chromatids
remain attached
Metaphase
plate
Homologous
chromosomes
separate
Homologous
chromosomes
Fragments
of nuclear
envelope
Telophase I and
Cytokinesis
Anaphase I
Microtubule
attached to
kinetochore
Cleavage
furrow
Sister chromatids
separate
Haploid daughter cells
forming
Fig. 13-9a
MITOSIS
MEIOSIS
Parent cell
Chromosome
replication
Prophase
Chromosome
replication
Prophase I
Homologous
chromosome
pair
2n = 6
Replicated chromosome
MEIOSIS I
Chiasma
Metaphase
Metaphase I
Anaphase
Telophase
Anaphase I
Telophase II
Haploid
n=3
Daughter
cells of
meiosis I
2n
Daughter cells
of mitosis
MEIOSIS II
2n
n
n
n
Daughter cells of meiosis II
n
Fig. 13-9b
SUMMARY
Property
Mitosis
Meiosis
DNA
replication
Occurs during interphase before
mitosis begins
Occurs during interphase before meiosis I begins
Number of
divisions
One, including prophase, metaphase,
anaphase, and telophase
Two, each including prophase, metaphase, anaphase, and
telophase
Synapsis of
homologous
chromosomes
Does not occur
Occurs during prophase I along with crossing over
between nonsister chromatids; resulting chiasmata
hold pairs together due to sister chromatid cohesion
Number of
daughter cells
and genetic
composition
Two, each diploid (2n) and genetically
identical to the parent cell
Four, each haploid (n), containing half as many chromosomes
as the parent cell; genetically different from the parent
cell and from each other
Role in the
animal body
Enables multicellular adult to arise from
zygote; produces cells for growth, repair,
and, in some species, asexual reproduction
Produces gametes; reduces number of chromosomes by half
and introduces genetic variability among the gametes
Fig. 13-11-3
Possibility 2
Possibility 1
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Daughter
cells
Combination 1
Combination 2
Combination 3
Combination 4
Fig. 13-12-5
Prophase I
of meiosis
Pair of
homologs
Nonsister
chromatids
held together
during synapsis
Chiasma
Centromere
TEM
Anaphase I
Anaphase II
Daughter
cells
Recombinant chromosomes
Mendelian Genetics
Fig. 14-2
TECHNIQUE
1
2
Parental
generation
(P)
Stamens
Carpel
3
4
RESULTS
First
filial
generation
offspring
(F1)
5
Fig. 14-3-3
EXPERIMENT
P Generation
(true-breeding
parents)
F1 Generation
(hybrids)

Purple
flowers
White
flowers
All plants had
purple flowers
F2 Generation
705 purple-flowered
plants
224 white-flowered
plants
Table 14-1
Fig. 14-4
Allele for purple flowers
Locus for flower-color gene
Allele for white flowers
Homologous
pair of
chromosomes
Fig. 14-5-3
P Generation
Purple flowers
Appearance:
Genetic makeup:
PP
Gametes:
White flowers
pp
p
P
F1 Generation
Appearance:
Genetic makeup:
Gametes:
Purple flowers
Pp
1/
2
1/
P
2
Sperm
F2 Generation
P
p
PP
Pp
Pp
pp
P
Eggs
p
3
1
p
Fig. 14-7
TECHNIQUE

Dominant phenotype,
unknown genotype:
PP or Pp?
Recessive phenotype,
known genotype:
pp
Predictions
If PP
Sperm
p
p
P
Pp
Eggs
If Pp
Sperm
p
p
or
P
Pp
Eggs
P
Pp
Pp
pp
pp
p
Pp
Pp
RESULTS
or
All offspring purple
1/2
offspring purple and
offspring white
1/2
Fig. 14-8
EXPERIMENT
YYRR
P Generation
Gametes
yyrr
YR

F1 Generation
yr
YyRr
Hypothesis of
dependent
assortment
Predictions
Hypothesis of
independent
assortment
Sperm
or
Predicted
offspring of
F2 generation
1/
4
Sperm
1/
2
YR
1/
2
1/
4
yR
1/
4
yr
YR
YYRR YYRr
YyRR
YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR
YyRr
yyRR
yyRr
YyRr
Yyrr
yyRr
yyrr
YR
YYRR
Eggs
1/
2
Yr
yr
1/
4
1/
2
YR
1/
4
YyRr
1/
4
Yr
Eggs
yr
YyRr
3/
4
yyrr
1/
4
yR
1/
4
Phenotypic ratio 3:1
1/
4
yr
9/
16
3/
16
3/
16
1/
16
Phenotypic ratio 9:3:3:1
RESULTS
315
108
101
32
Phenotypic ratio approximately 9:3:3:1
The Multiplication and Addition Rules
Applied to Monohybrid Crosses
• The multiplication rule states that the probability that
two or more independent events will occur together is
the product of their individual probabilities
• Probability in an F1 monohybrid cross can be
determined using the multiplication rule
• Segregation in a heterozygous plant is like flipping a
coin: Each gamete has a12 chance of carrying the
dominant allele and a 12 chance of carrying the
recessive allele
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Fig. 14-9

Rr
Segregation of
alleles into eggs
Rr
Segregation of
alleles into sperm
Sperm
1/
2
R
R
1/
2
r
R
R
R
r
1/
4
Eggs
r
1/
2
1/
2
r
1/
4
r
r
R
1/
4
1/
4
• The rule of addition states that the probability that
any one of two or more exclusive events will occur
is calculated by adding together their individual
probabilities
• The rule of addition can be used to figure out the
probability that an F2 plant from a monohybrid
cross will be heterozygous rather than homozygous
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Solving Complex Genetics Problems
with the Rules of Probability
• We can apply the multiplication and addition rules
to predict the outcome of crosses involving
multiple characters
• A dihybrid or other multicharacter cross is
equivalent to two or more independent
monohybrid crosses occurring simultaneously
• In calculating the chances for various genotypes,
each character is considered separately, and then
the individual probabilities are multiplied together
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Fig. 14-10-3
P Generation
Red
CRCR
White
CWCW
CR
Gametes
CW
Pink
CRCW
F1 Generation
Gametes
1/
2
CR
1/
2
CW
Sperm
1/
2
CR
1/
2
CW
F2 Generation
1/
2
CR
Eggs
1/
2
CRCR
CRCW
CRCW
CWCW
CW
Fig. 14-11
Allele
IA
Carbohydrate
A
IB
B
none
i
(a) The three alleles for the ABO blood groups
and their associated carbohydrates
Genotype
Red blood cell
appearance
Phenotype
(blood group)
IAIA or IA i
A
IBIB or IB i
B
IAIB
AB
ii
O
(b) Blood group genotypes and phenotypes
Fig. 14-13

AaBbCc
AaBbCc
Sperm
1/
Eggs
1/
8
1/
8
1/
8
1/
8
1/
8
1/
8
1/
1/
8
8
1/
8
1/
64
15/
8
1/
1/
8
8
8
1/
8
1/
8
1/
8
Phenotypes:
Number of
dark-skin alleles:
1/
64
0
6/
64
1
15/
64
2
20/
3
64
4
6/
64
5
1/
64
6
Fig. 14-14
Fig. 14-15b
1st generation
(grandparents)
2nd generation
(parents, aunts,
and uncles)
Ww
ww
Ww
ww
Ww ww ww Ww
Ww
ww
3rd generation
(two sisters)
WW
or
Ww
Widow’s peak
ww
No widow’s peak
(a) Is a widow’s peak a dominant or recessive trait?
Fig. 14-15c
1st generation
(grandparents)
2nd generation
(parents, aunts,
and uncles)
Ff
FF or Ff ff
Ff
ff
ff
Ff
Ff
Ff
ff
ff
FF
or
Ff
3rd generation
(two sisters)
Attached earlobe
Free earlobe
(b) Is an attached earlobe a dominant or recessive trait?
Fig. 14-UN2
Degree of dominance
Example
Description
Complete dominance
of one allele
Heterozygous phenotype
same as that of homozygous dominant
Incomplete dominance
of either allele
Heterozygous phenotype
intermediate between
the two homozygous
phenotypes
PP
Pp
CRCR
Codominance
Multiple alleles
Pleiotropy
Heterozygotes: Both
phenotypes expressed
In the whole population,
some genes have more
than two alleles
One gene is able to
affect multiple
phenotypic characters
CRCW CWCW
IAIB
ABO blood group alleles
IA , IB , i
Sickle-cell disease
Chromosomal Theory of Inheritance
Fig. 15-2
P Generation
Yellow-round
seeds (YYRR)
Y
Y
R
r

R
y
Green-wrinkled
seeds ( yyrr)
y
r
Meiosis
Fertilization
y
R Y
Gametes
r
All F1 plants produce
yellow-round seeds (YyRr)
F1 Generation
R
R
y
r
Y
Y
LAW OF SEGREGATION
The two alleles for each gene
separate during gamete
formation.
y
r
LAW OF INDEPENDENT
ASSORTMENT Alleles of genes
on nonhomologous
chromosomes assort
independently during gamete
formation.
Meiosis
R
r
Y
y
r
R
Y
y
Metaphase I
1
1
R
r
Y
y
r
R
Y
y
Anaphase I
R
r
Y
y
Metaphase II
r
R
Y
y
2
2
Y
Y
Gametes
R
1/
4 YR
F2 Generation
R
y
r
Y
Y
y
r
r
1/ yr
4
r
1/
4 Yr
y
R
y
R
1/ yR
4
An F1  F1 cross-fertilization
3
3
9
:3
:3
:1
Fig. 15-4c
CONCLUSION
P
Generation
X
X
w+

w+
X
Y
w
Eggs
F1
Generation
Sperm
w+
w+
w+
w
w+
Eggs
F2
Generation
w
w+
Sperm
w+
w+
w
w
w
w+
Fig. 15-7
XNXN
Sperm Xn

XnY
Sperm XN
Y
Eggs XN
XNXn XNY
XN
XNXn XNY
(a)
XNXn
Eggs
(b)

XNY
XNXn
Sperm Xn
Y
XN
XNXN XNY
Xn
XnXN
Eggs XN
XnY
Xn
(c)

XnY
Y
XNXn XNY
XnXn
XnY
Fig. 15-8
X chromosomes
Early embryo:
Two cell
populations
in adult cat:
Active X
Allele for
orange fur
Allele for
black fur
Cell division and
X chromosome
inactivation
Active X
Inactive X
Black fur
Orange fur
Fig. 15-UN1
b vg
b+ vg+
Parents
in testcross
Most
offspring

b vg
b vg
b+ vg+
b vg
or
b vg
b vg
Fig. 15-9-4
EXPERIMENT
P Generation (homozygous)
Wild type
(gray body,
normal wings)
Double mutant
(black body,
vestigial wings)

b b vg vg
b+ b+ vg+ vg+
F1 dihybrid
(wild type)
Double mutant
TESTCROSS

b+ b vg+ vg
Testcross
offspring
b b vg vg
Eggs
b+ vg+
Wild type
(gray-normal)
b vg
b+ vg
b vg+
Blackvestigial
Grayvestigial
Blacknormal
b vg
Sperm
b b vg vg b+ b vg vg b b vg+ vg
b+ b vg+ vg
PREDICTED RATIOS
If genes are located on different chromosomes:
1
:
1
:
1
:
1
If genes are located on the same chromosome and
parental alleles are always inherited together:
1
:
1
:
0
:
0
965
:
944
:
206
:
185
RESULTS
Fig. 15-UN2
Gametes from yellow-round
heterozygous parent (YyRr)
Gametes from greenwrinkled homozygous
recessive parent ( yyrr)
YR
yr
Yr
yR
YyRr
yyrr
Yyrr
yyRr
yr
Parentaltype
offspring
Recombinant
offspring
Fig. 15-10
Testcross
parents
Gray body, normal wings
(F1 dihybrid)
Replication
of chromosomes
Meiosis I
Black body, vestigial wings
(double mutant)
b+ vg+
b vg
b vg
b vg
Replication
of chromosomes
b+ vg+
b vg
b+ vg+
b vg
b vg
b vg
b vg
b vg
b+ vg+
Meiosis I and II
b+ vg
b vg+
b vg
Meiosis II
Recombinant
chromosomes
Eggs
Testcross
offspring
b vg
b+ vg+
b+ vg
b vg+
965
944
206
185
Wild type
(gray-normal)
Blackvestigial
Grayvestigial
Blacknormal
b+ vg+
b vg
b+ vg
b vg+
b vg
b vg
b vg
b vg
Parental-type offspring
Recombination
frequency
=
Recombinant offspring
391 recombinants
2,300 total offspring
 100 = 17%
b vg
Sperm
Fig. 15-11
RESULTS
Recombination
frequencies
9%
Chromosome
9.5%
17%
b
cn
vg
Fig. 15-12
Short
aristae
0
Long aristae
(appendages
on head)
Mutant phenotypes
Black
body
48.5
Gray
body
Cinnabar
eyes
57.5
Red
eyes
Vestigial
wings
67.0
Normal
wings
Wild-type phenotypes
Brown
eyes
104.5
Red
eyes
Fig. 15-13-3
Meiosis I
Nondisjunction
Meiosis II
Nondisjunction
Gametes
n+1
n+1
n–1
n–1
n+1
n–1
n
Number of chromosomes
(a) Nondisjunction of homologous
chromosomes in meiosis I
(b) Nondisjunction of sister
chromatids in meiosis II
n
Fig. 15-15
(a)
(b)
(c)
(d)
A B C D E
F G H
A B C D E
F G H
A B C D E
F G H
A B C D E
F G H
Deletion
Duplication
Inversion
A B C E
F G H
A B C B C D E
A D C B E
F G H
M N O C D E F G H
Reciprocal
translocation
M N O P Q R
F G H
A B P Q R
Fig. 15-16
Fig. 15-17
Normal chromosome 9
Normal chromosome 22
Reciprocal
translocation
Translocated chromosome 9
Translocated chromosome 22
(Philadelphia chromosome)