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Figure 13.1
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Genetics Assignments:
1. Family Photo and Character Traits List (5
similarities/5 differences) – DUE WEDS. 1/7
2. Genetics (Ch. 11/14) Vocab PART 2 – DUE
FRIDAY, 1/9
3. Genetics (Ch. 11/14) Objectives PART 2 –
DUE Monday, 1/12
4. Genetics Disease Research Project – DUE
TUES. 1/20.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Chapters 11 & 14
GENETICS PART 2:
Patterns of Inheritance
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Living organisms are distinguished by their
ability to reproduce their own kind
Genetics is the scientific study of heredity and
variation
Heredity is the transmission of traits from one
generation to the next
Variation is demonstrated by the differences in
appearance that offspring show from parents
and siblings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
© 2011 Pearson Education, Inc.
The historical roots of genetics:
•Early 19th century: traits from mom and dad blend like paints to
form kid’s traits
Gregor Mendel (1840’s) : “Father of modern genetics”
• Mendel crossed pea plants that differed in certain
characteristics (traits) and traced from generation to
generation; used a mathematical approach
• Why did he choose pea plants?
• Crossing of traits:
Self fertilize (True breed) – cross pollen and egg from same
parent plant to get identical offspring
Cross Fertilize (hybrid) – cross pollen from one parent plant
with the egg of a different parent plant
Gregor mendel
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Parents
(P)
• P generation is true-breeding –
Parent generation
– F1 generation = Hybrid
offspring of P (parents)
White
– F2 generation = offspring of
F1 plants crossed
– F3 generation = offspring of
F2 plants crossed
And so on…
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Purple
Offspring
(F1)
• Mendel hypothesized that there are alternative
forms of factors (genes) = units that determine
heritable traits
Flower color
Purple
White
Axial
Terminal
Seed color
Yellow
Green
Seed shape
Round
Wrinkled
Flower position
Pod shape
Inflated
Constricted
Pod color
Green
Yellow
Stem length
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Tall
Dwarf
From his experimental data, Mendel deduced that an organism has two
genes (alleles) for each inherited characteristic
• For each characteristic (trait), an organism inherits 2
alleles, one from each parent.
Think of TRAITS as CATEGORIES and
ALLELES as OPTIONS within each
category!
P generation
(true-breeding
parents)
Examples:
•Flower Color (trait)

Purple flowers
White flowers
F1 generation
All plants have
purple flowers
•Purple or White (alleles)
Fertilization
among F1 plants
(F1  F1)
F2 generation
3
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4 of plants
have purple flowers
1
4 of plants
have white flowers
Phenotype = physical appearance of the allele
for a specific trait (purple/white flower for flower color trait)
Genotype = genetic makeup the alleles that
represent the phenotype (one dominant, one
recessive; or 2 dominant alleles and 2 recessives)
DNA from the Beginning Animations
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Dominant and Recessive Alleles:
• If the 2 alleles of an inherited pair are different,
then one determines the organism’s
appearance and is called the dominant allele.
(Dominant will usually show up more often!)
– The other allele has no noticeable effect on
the organism’s appearance and is called
the recessive allele. (Is present but does not show
up in the appearance)
* If dominant allele is present, it takes
over and outweighs the recessive!
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Dominant and Recessive alleles:
In a genetic cross, CAPITAL letters are
used to represent DOMINANT alleles and
lower case letters represent the
recessive alleles.
– MUST USE SAME LETTER FOR EACH
TRAIT! (Doesn’t matter the letter you
choose!)
Example:
Flower Color (trait) T = purple, t = white
Pea Color
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R=yellow, r =green
HOMOZYGOUS and HETEROZYGOUS
•When 2 of the SAME ALLELES are present, it is
HOMOZYGOUS for that trait.
With
homozygous,
you must clarify
hh = homozygous recessive
which alleleeither
Dominant
•When 2 DIFFERENT alleles are present, it or
is termed
recessive!
HH = homozygous dominant
HETEROZYGOUS for the trait.
• Hh= heterozygous
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
•We can look at the alleles from each parent to
determine the probability of those alleles being
passed on to offspring.
PUNNETT SQUARE:
Shows a genetic mixing (cross) of alleles from
both parents for specific traits.
Punnett Square are use to PREDICT
PROBABILITIES and see inheritance patterns
for specific traits!
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Trait= Flower Color
H =purple
Parent #2
H
h = white
H
h
Hh
Hh
PARENT
#1
h
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Hh
Hh
Trait= Flower Color
* If Dominant allele is present, it
takes over and outweighs the
recessive!
H =purple h = white
H
Genotype =genetic makeup
(represented by letters!)
Parent 1 = hh
homozygous recessive
H
h
Hh
Parent 2 = HH
homozygous dominant
Offspring= 100% Hh
Heterozygous
Phenotype =physical
appearance (what the letters
represent!)
Parent 1 = white
Hh
Probability of one
offspring from parent
cross!
h
Parent 2 = purple
Offspring= 100% purple
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Hh
Hh
LET’S PRACTICE!!!
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Homologous chromosomes bear the two alleles
for each characteristic
– Reside at the same locus (point) on
homologous chromosomes Dominant
allele
Gene loci
P
P
a
B
a
b
Recessive
allele
Genotype:
PP
Homozygous
for the
dominant allele
aa
Homozygous
for the
recessive allele
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Bb
Heterozygous
Mendel’s law of segregation
P plants
Predicts that allele
pairs from each parent
separate (segregate)
from each other
during the production
of gametes
(sperm/eggs)
Genetic makeup (alleles)
PP
pp
All P
All p
Gametes
F1 plants
(hybrids)
All Pp
1
P
2
Gametes
1
p
2
Sperm
P
p
F2 plants Phenotypic ratio
3 purple : 1 white
P
PP
Pp
p
Pp
pp
Eggs
Genotypic ratio
1 PP: 2 Pp: 1 pp
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Mendel’s law of independent assortment
– States that alleles of a pair segregate independently of
other allele pairs during gamete formation
Hypothesis: Independent assortment
Hypothesis: Dependent assortment
RRYY
P generation
Gametes
rryy
RRYY
ry
RY
rryy
Gametes

RY
ry
RrYy
RrYy
F1 generation
Sperm
Sperm
1
2 RY
1
2
ry
1
4
1
RY
2
F2 generation
Eggs
1
2
1
4
1
4
Eggs
ry
1
4
Actual results
contradict hypothesis
Figure 9.5 A
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1
4
RY
1
4
ry
1
4
RY
1
4
ry
RY
RRYY
RrYY
RRYy
RrYY
rrYY
RrYy
RrYy
ry
rrYy
Ry
RRYy
RrYy
RRyy
Rryy
RrYy
rrYy
Rryy
rryy
ry
Actual results
support hypothesis
9
16
Yellow
round
3
16
Green
round
3
16
1
16
Yellow
wrinkled
Green
wrinkled
9.8 Genetic traits in humans can be tracked through family pedigrees.
Dd
Joshua
Lambert
D?
John
Eddy
Dd
Abigail
Linnell
D?
Hepzibah
Daggett
Female
dd
Jonathan
Lambert
D?
Abigail
Lambert
Dd
Elizabeth
Eddy
Male
Mating
Dd
Dd
dd
Dd
Dd
Dd
dd
Female Male
Deaf
Hearing
Figure 9.8 B
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Offspring
Copyright
2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Table©9.9
Recessive Disorders- Most human genetic disorders are recessive
Parents
Normal
Dd

Normal
Dd
Sperm
D
D
Offspring
DD
Normal
d
Dd
Normal
(carrier)
Eggs
d
Dd
Normal
(carrier)
Figure 9.9 A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
dd
Deaf
Dominant Disorders- Some human genetic disorders are dominant
Parents
Dwarf
Dd
Normal
dd
Sperm
Achondroplasia – cause
of dwarfism
D
d
Offspring

Dd
Dwarf
d
dd
Normal
Eggs
d
Figure 9.9 B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Dd
Dwarf
dd
Normal
9.10 New technologies can provide insight into genetic legacy
Identifying Carriers
• For an increasing number of genetic disorders, tests
are available that can distinguish carriers of genetic
disorders and can provide insight for reproductive decisions
Fetal Testing: Amniocentesis and chorionic villus
sampling (CVS) allow doctors to remove fetal cells that can
be tested for genetic abnormalities
Fetal Imaging- Ultrasound imaging uses sound waves to
produce a picture of the fetus
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Chorionic villus sampling (CVS)
Amniocentesis
Needle inserted
Ultrasound
monitor
through abdomen to
extract amniotic fluid
Fetus
Suction tube inserted
through cervix to extract
tissue from chorionic villi
Fetus
Placenta
Uterus
Ultrasound
monitor
Placenta
Chorionic
villi
Cervix
Cervix
Uterus
Amniotic
fluid
Centrifugation
Fetal
cells
Fetal
cells
Several
weeks
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Figure 9.10 A
Biochemical
tests
Karyotyping
Several
hours
Figure 9.10 B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Newborn Screening
• Some genetic disorders can be detected at
birth, by simple tests that are now routinely
performed in most hospitals in the United
States
Ethical Considerations
• New technologies such as fetal imaging and
testing raise new ethical questions
(Think about “Designer Babies”!)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
NON-MENDELIAN
GENETICS
ALL OF THE FOLLOWING ARE EXCEPTIONS
TO MENDEL’S RULES!!!
•Mendel’s principles are valid for all sexually
reproducing species, HOWEVER, genotype often
does NOT dictate phenotype in the simple way
his laws described.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• When an offspring’s phenotype is in between the phenotypes of
its parent, it exhibits incomplete dominance. (3rd phenotype
shows up!)
P generation
Red
RR

White
rr
r
R
Gametes
F1 generation
Pink
Rr
1
2
Gametes
R
1
2
r
Sperm
1
2
F2 generation
Figure 9.12 A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
R
1
2
r
1
2
R
Red
RR
Pink
rR
1
2
r
Pink
Rr
White
rr
Eggs
Codominance
• In a population, multiple alleles (2 or more options)
often exist for a single trait.
Example: The ABO blood type in humans
– The alleles for A and B blood types are
codominant and both are expressed in
the phenotype
Roan fur coloring on
cows/horses –
2 separate colors show up
equally (red/white)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Figure 9.13
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Polygenic inheritance- creates a multiple variations of
phenotypes

P generation
aabbcc
(very light)

F1 generation
AaBbCc
1
8
F2 generation
AABBCC
(very dark)
1
8
AaBbCc
Sperm
1
1
1
8
8
8
1
8
1
8
1
8
1
8
1
8
Eggs
6
64
15
64
20
64
1
8
20
64
15
64
1
8
1
8
1
8
Figure 9.15
1
64
1
8
1
8
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6
64
1
64
Skin color
15
64
6
64
1
64
9.20 Crossing over produces new combinations of alleles
• Crossing over can separate linked alleleS
producing gametes with recombinant
chromosomes
A
B
a
b
A
b
a
B
A B
a
b
Tetrad
Crossing over
Gametes
Figure 9.20 A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
SEX CHROMOSOMES AND SEX-LINKED GENES
• In mammals, a male has one X chromosome and one Y
chromosome and a female has two X chromosomes.
• The Y chromosome has genes for the development of
testes.
• The absence of a Y chromosome allows ovaries to
develop.
(male)
44
Parents’
+
diploid
XY
cells
22
+
X
Figure 9.22 A
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(female)
44
+
XX
22
+
Y
Sperm
22
+
X
44
+
XX
44
+
XY
Offspring
(diploid)
Egg
• The inheritance pattern of sex-linked genes is reflected
in females and males.
• A male receiving a single X-linked allele from his
mother will have the disorder
• A female has to receive the allele from both parents
to be affected
Female

XR XR
Male
Female
Xr Y
XR Xr

Eggs XR
Y
XR Xr
XR Y
Female
XR Y
XR Xr
XR
Figure 9.23 B
Xr Y
Sperm
XR
Y
XR XR
XR Y
XR
Xr
Y
XR Xr
XR Y
Xr Xr
Xr Y
Eggs
Eggs
R = red-eye allele
r = white-eye allele
Male

Sperm
Sperm
Xr
Male
Xr
Xr XR
Figure 9.23 C
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Xr Y
Xr
Figure 9.23 D
Sex Linked
• Most sex-linked human disorders are due to
recessive alleles and are mostly seen in
males
Examples: Hemophilia, Color Blindness, and
Duchenne Muscular Dystrophy
Queen
victoria
Albert
Alice
Louis
Alexandra
Figure 9.24 A
Figure 9.24 B
Czar
Nicholas II
of Russia
Alexis
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