Chapter 29:
Heredity
Clarence E. McClung - one of the first (1901) to deduce that
chromosomes determine the sex of offspring.
Figure 29.1
Figure 29.1c
1 Removed stamens
from purple flower
APPLICATION By crossing (mating) two true-breeding
varieties of an organism, scientists can study patterns of
inheritance. In this example, Mendel crossed pea plants
that varied in flower color.
TECHNIQUE
2 Transferred sperm-
bearing pollen from
stamens of white
flower to eggbearing carpel of
purple flower
Parental
generation
(P)
3 Pollinated carpel
Stamens
Carpel (male)
(female)
matured into pod
4 Planted seeds
from pod
TECHNIQUE
RESULTS
When pollen from a white flower fertilizes
eggs of a purple flower, the first-generation hybrids all have purple
First
flowers. The result is the same for the reciprocal cross, the transfer
generation
of pollen from purple flowers to white flowers.
offspring
(F1)
5 Examined
offspring:
all purple
flowers
EXPERIMENT True-breeding purple-flowered pea plants and
white-flowered pea plants were crossed (symbolized by ). The
resulting F1 hybrids were allowed to self-pollinate or were crosspollinated with other F1 hybrids. Flower color was then observed
in the F2 generation.

P Generation
(true-breeding
parents)
Purple
flowers
White
flowers
F1 Generation
(hybrids)
All plants had
purple flowers
RESULTS Both purple-flowered plants and whiteflowered plants appeared in the F2 generation. In Mendel’s
experiment, 705 plants had purple flowers, and 224 had white
flowers, a ratio of about 3 purple : 1 white.
F2 Generation
Allele for purple flowers
Locus for flower-color gene
Allele for white flowers
Homologous
pair of
chromosomes
Each true-breeding plant of the
parental generation has identical
alleles, PP or pp.
Gametes (circles) each contain only
one allele for the flower-color gene.
In this case, every gamete produced
by one parent has the same allele.
Union of the parental gametes
produces F1 hybrids having a Pp
combination. Because the purpleflower allele is dominant, all
these hybrids have purple flowers.
When the hybrid plants produce
gametes, the two alleles segregate,
half the gametes receiving the P
allele and the other half the p allele.
P Generation

Appearance:
Purple flowerWhite flowers
Genetic makeup:
PP
pp
Gametes:
P
p
F1 Generation
Appearance:
Genetic makeup:
Gametes:
Purple flowers
Pp
Each true-breeding plant of the
parental generation has identical
alleles, PP or pp.
Gametes (circles) each contain only
one allele for the flower-color gene.
In this case, every gamete produced
by one parent has the same allele.
Union of the parental gametes
produces F1 hybrids having a Pp
combination. Because the purpleflower allele is dominant, all
these hybrids have purple flowers.
When the hybrid plants produce
gametes, the two alleles segregate,
half the gametes receiving the P
allele and the other half the p allele.
This box, a Punnett square, shows
all possible combinations of alleles
in offspring that result from an
F1  F1 (Pp  Pp) cross. Each square
represents an equally probable product
of fertilization. For example, the bottom
left box shows the genetic combination
resulting from a p egg fertilized by
a P sperm.
P Generation

Appearance:
Purple flowerWhite flowers
Genetic makeup:
PP
pp
Gametes:
p
P
F1 Generation
Appearance:
Genetic makeup:
Gametes:
Purple flowers
Pp
1/
2
1/
P
p
F1 sperm
P
p
PP
Pp
F2 Generation
P
F1 eggs
p
pp
Pp
Random combination of the gametes
results in the 3:1 ratio that Mendel
observed in the F2 generation.
2
3
:1
Phenotype
Purple
3
Purple
Genotype
PP
(homozygous)
1
Pp
(heterozygous)
2
Pp
(heterozygous)
Purple
1
White
pp
(homozygous)
Ratio 3:1
Ratio 1:2:1
1
Table 14.2 Determination of ABO
Blood Group by Multiple Alleles

BbCc
BbCc
Sperm
1⁄
BC
4
1⁄
4
bC
1⁄
4
1⁄
Bc
4
bc
Eggs
1⁄
1⁄
4
BC
BBCC
BbCC
BBCc
BbCc
4
bC
BbCC
bbCC
BbCc
bbCc
1⁄
1⁄
4
Bc
BBCc
BbCc
BBcc
4
bc
BbCc
bbCc
Bbcc
9⁄
16
3⁄
16
Bbcc
4⁄
bbcc
16
Skin Color

AaBbCc
AaBbCc
aabbcc Aabbcc AaBbcc AaBbCc AABbCcAABBCc AABBCC
20⁄
64
15⁄
6⁄
64
64
1⁄
64
Pedigree analysis
Ww
ww
Ww ww ww Ww
WW
or
Ww
ww
Ww
Ww
ww
First generation
(grandparents)
Second generation
(parents plus aunts
and uncles)
(a) Dominant trait (widow’s peak)
FF or Ff
Ff
Ff
Third
generation
(two sisters)
ww
Widow’s peak
Ff
No Widow’s peak
Attached earlobe
ff
ff
Ff
Ff
Ff
ff
ff
FF
or
Ff
Free earlobe
(b) Recessive trait (attached earlobe)
Figure 14.15 Achondroplasia
(b) Chorionic villus sampling (CVS)
(a) Amniocentesis
Amniotic
fluid
withdrawn
A sample of chorionic villus
tissue can be taken as early
as the 8th to 10th week of
pregnancy.
A sample of
amniotic fluid can
be taken starting at
the 14th to 16th
week of pregnancy.
Fetus
Fetus
Suction tube
Inserted through
cervix
Centrifugation
Placenta
Placenta
Uterus
Chorionic viIIi
Cervix
Fluid
Fetal
cells
Fetal
cells
Biochemical tests can be
Performed immediately on
the amniotic fluid or later
on the cultured cells.
Fetal cells must be cultured
for several weeks to obtain
sufficient numbers for
karyotyping.
Biochemical
tests
Several
weeks
Several
hours
Karyotyping
Karyotyping and biochemical
tests can be performed on
the fetal cells immediately,
providing results within a day
or so.
Figure 29.2
Figure 29.3
Figure 29.4
Figure 29.5
Figure 29.6
Figure 29.7
Table 29.1
Table 29.2
I > Clicker Question
General Topic Question
The condition in which the body maintains homeostasis would best
be described as
A)
the highest possible metabolism.
B)
a state that fluctuates widely from person to person.
C)
a relatively stable internal environment depending
upon environmental conditions.
D)
a static state with absolutely no deviation from preset
points (120/80 being normal blood pressure, for
example).
E)
Two of the above is correct.
General Topic Question
When you think of the lymphatic system, which of the following
are correct?
A)
Lymph is a watery solution that typically pools
and collects on the inside of the cells and needs
to be collected and transported back to the
lymph nodes.
B)
Fluid moves away from the circulatory system
while in lymphatic vessels.
C)
This system houses many of the immune
response cells of the body.
D)
Two of the above are correct.
E)
None of the above are correct.
Semester Specific General Question
Hormones used in the short term stress response
would be
A)
aldosterone and norepinephrine.
B)
cortisol and thymosin.
C)
epinephrine and norepinephrine.
D)
aldosterone and adrenalin.
E)
Two of the above are correct.
Semester Specific General Question
Which statement best describes veins?
A)
All carry blood toward the heart.
B)
None carry oxygenated blood.
C)
Most contain valves to prevent the
backflow of blood.
D)
Two of the above are descriptive of veins.
E)
All of the above are correct.
New Information Style Question
In a pedigree chart, a female who does not
demonstrate the trait being studied is represented
by a
A)
darkened square.
B)
clear diamond.
C)
clear circle.
D)
darkened triangle.
E)
darkened oval.
The reason the hypodermis is protective is
A)
it has no delicate blood vessels and can therefore
absorb more shock.
B)
because a major part of its makeup is adipose, and
adipose tissue serves as an effective shock
absorber... minimizing damage.
C)
it is located just below the epidermis and protects
the dermis from shock.
D)
All of the above are correct.
I > Clicker Question
The process by which liquid-containing vesicles are expelled out of a
cell is called
A)
pinocytosis.
B)
phagocytosis.
C)
exocytosis.
D)
receptor-mediated endocytosis.
E)
channel-mediated transport.
The muscle type found in the vena cava (the blood vessel that
brings blood to the heart) is
A)
cardiac.
B)
smooth.
C)
skeletal.
D)
voluntarily controlled.
E)
Two of the above are correct
An exocrine gland
A)
secretes material into the bloodstream.
B)
expels material outside the body.
C)
would be a likely mechanical device for the
expression of elastophosphoids.
D)
Two of the above are correct.
E)
All of the above are
Coating the skin and hair with oil is an activity of
A)
the sebaceous glands.
B)
a type of endocrine gland.
C)
a clathrin mediated receptor interaction.
D)
Two of the above are correct.
E)
All of the above are
You are a new medical intern at St. Mary’s of Michigan Hospital
in Saginaw. Dee Gordon, the famous player for the Great
Lakes Loons, comes into your office saying his previous
doctor told him he had bursitis, you immediately would
recognize that this disorder would be designated as
inflammation of
A)
an epiphyseal disk.
B)
a cavity within a long bone filled with synovial
fluid.
C)
a membrane sac containing fluid, probably at
the elbow.
D)
a cartilage at a joint, such as the knee.
Think logically for this question.... If a muscle were stretched to the
point where actin filaments and myosin filaments no longer
overlapped,
A)
ADP consumption would increase since the
sarcomere is “trying” to contract.
B)
cross-bridge attachment would be optimum because
of all the free binding sites on actin.
C)
no muscle tension could be generated.
D)
maximum force production would result since the
muscle has a maximum range of travel.
E)
Two of the above are
I > Clicker Question
Homeostasis of calcium ion concentration depends upon which of the
following hormones?
A)
Parathymus hormone
B)
Calcitonin
C)
Thyroxine
D)
Two of the above are correct.
E)
None of the above are correct.
1) In total cross sectional area, there is more area devoted to
capillaries than arteries and therefore 2) the blood pressure in
the capillary beds is much lower.
A)
Statements 1 & 2 are both true.
B)
Statement 1 is true and statement 2 is false.
C)
Statement 1 is false and statement 2 is true.
D)
Statements 1 & 2 are both false.
The term given to the shape of the erythrocyte in
humans is
A)
dual convex disk.
B)
biconcave disk.
C)
sickle shaped cell.
D)
myopic disk.
E)
None of the above are correct.
What is the main function of binocular vision?
A)
Depth perception
B)
Color vision
C)
Vision in dim light
D)
Accommodation for near vision
E)
Two of the above are correct.
Human egg and sperm are similar in that
A)
about the same number of each are
produced per month.
B)
they have the same degree of motility.
C)
they are about the same size.
D)
they have the same number of
chromosomes.
The chemical and mechanical processes of food breakdown are
called
A)
absorption.
B)
ingestion.
C)
digestion.
D)
secretion.