Download Freeman 1e: How we got there

Chapter 10.1
Genetics
Baker Academy Biology
Hickox: Baker High School
1
Chapter 10
Genetics
KEY CONCEPTS
•
Apply Mendel’s laws to determine phenotypic and genotypic
probabilities of offspring
• Defining important genetic terms, including monohybrid cross,
phenotype, homozygous, heterozygous, recessive trait,
incomplete dominance, codominance, and allele;
• Interpreting inheritance patterns shown in graphs and charts;
• Calculate genotypic and phenotypic percentages and ratios
using a Punnett square.
• The fact that the human body is formed from cells that contain
two copies of each chromosome — and therefore two copies of
each gene -- explains many features of human heredity, such as
how variations that are hidden in one generation can be
expressed in the next.
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Chapter 210
• Resultant of his experiments with pea plants, Mendel generated four
hypotheses:
• For each inherited trait, an individual has two copies of the gene –
one from each parent.
• There are alternative versions of genes
• When two different alleles occur together, one of them may be
completely expressed, while the other may have no observable effect
on the organism’s appearance.
• When gametes are formed, the alleles for each gene in an individual
separate independently of one another.
• Patterns of heredity can be complex because most traits are not
controlled by simple dominant-recessive alleles
• Vocabulary: Heredity, Genetics, Gene, Recessive, Dominant, DNA,
Chromosome, Gregor Mendel, Genotype, Alleles, Heterzygogous,
Homozygous, phenotype, hybrid, cross pollinaion, Self pollination,
Law of Segregation, Law of Independent Assortment, Codominance,
Incomplete dominance, Pedigree, Punnett square, Monohybrid cross,
Dihybrid cross.
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Mendel’s Laws of Heredity
Why Mendel Succeeded
Gregor Mendel was the first person to
predict traits. The study of traits is called
(1)_____________
•(2) __________ is the passing on of
characteristic from parents to offspring.
• These characteristics are called
(3)________.
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Mendel’s Laws of Heredity
• Mendel used garden (4) peas for his
experiments.
• Garden peas produce male and female
sex cells called (5)__________
• (6)_____________occurs when male sex
cells units with the female sex cell and
produces a new fertilized cell called a
(7)_____________
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Mendel’s Laws of Heredity
• In garden peas, as with most flowers, the
male sex cells are grains of (8)________.
• When pollen is transferred from the male
reproductive organ to the female reproductive
organ, is called (9)___________
•
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Mendel’s Laws of Heredity
• Garden peas are
(10)__________________the
pollen from a flower pollinates
the female sex cell within that
same flower.
• Mendel wanted to unite
gametes of different plants .
Mendel opened the petals of
flower and removed the male
reproductive organs and dusted
the female organ with the polled
from a different plant. This is
called (11)_______________.
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How did Mendel proceed?
• Mendel studied one trait at a time
• Studied tallness first
• Used plants that were (12)____________
 means they always produce that trait
• Took pollen from a true-breeding tall
pea plant and crossed-pollinated a truebreeding short plant. The study of one
trait only is called a (13)____________
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What were the results?
• 6’ tall true-breeding X 2’ short true-breeding
• Results? (14)________________ The short
did (15)_______appear in the first generation or
(16)_____.
• Mendel allowed the offspring to self-pollinate
and out of 1000 plats in the second generation
or (17)___, ¾ or (18)_____ were tall and ¼
or 25% were short. The ratio was 3:1 or 3 tall
to 1 short
• Mendel used similar (19)___________crosses
with seven different traits. (wrinkled or round,
yellow or green) etc.
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Mendel’s Laws of Heredity
• In each case the F1 generation produced
100% for one of the traits and one trait did not
appear.
• In each case the F2 produced a ¾ to ¼ or
(20)______ratio
• We now know that two factors control each of
its traits. Genes exist in alternative forms: tall
and short or round and wrinkled. The
alternative forms are called (21)_________
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Mendel’s Laws of Heredity
• An organism can have two (22)
________for tallness, two alleles for
shortness, or one allele for tallness and
one allele for shortness.
• The organism receives or inherits one
allele from the female parent and one
allele from the male parent.
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What is dominance?
• Mendel called the observed tall trait that was
only observed in the F1 generation as
(23)__________
• The trait that disappeared in the F1 and later
returned in the F2 is called (24)__________
• The allele for tall plants is (25)___________ to
the allele for short plants.
• The plants with two alleles for tallness were (26)____
• The plants with two alleles for shortness were (27)___
•The plants with one allele for tallness and one allele for
short was (28)__________
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12
What is dominance?
• We us an uppercase “letter” for the
dominant allele and a lowercase letter is
used for a recessive allele.
•The dominant allele is always written first.
• Every organism has two alleles for each
gene and when gametes are produced the
alleles separate. Each gamete receives one
of these alleles, called
(29)________________
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Phenotype and Genotype
• The way an organism looks and behaves
is called (30)____________
• The phenotype of a tall plant is tall.
• This plant can have an allele
combination of (31)____ or (32)_____
• The allele combination of an organism
is called the (33)__________
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Mendel’s Laws of Heredity
tt
TT
Tt
3 - Tall
1 – Short
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Mendel’s Laws of Heredity
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Mendel’s Laws of Heredity
Punnett Square
• method to predict proportions of
possible genotypes in offspring.
T
T
t
Tt
Tt
t
Tt
Tt
T
t
T
TT
Tt
t
Tt
tt
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Mendel’s Laws of Heredity
Punnett Square
• method to predict proportions of
possible genotypes in offspring.
T
T
t
Tt
Tt
t
Tt
Tt
T
t
T
TT
Tt
t
Tt
tt
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Choosing the Traits- Mendel’s 7
Easily Recognizable
Traits: Seed shape, seed
color, pod shape, pod
color, flower color, flower
and pod position, and
stem length
(34) PHENOTYPE
(physical characteristic)
One can tell what a dog’s
phenotype is by looking at
him
(35) HYBRIDS
(offspring with different traits)
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11.1
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The Principle of (36)___________
HOMOZYGOUS (AA or aa)
HETEROZYGOUS (Aa)
Monohybrid
cross (single
trait)
PUNNET SQUARES
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2011.2
Multiple Alleles & Polygenetic Traits
• some blood from individuals
clump when mixed with other
blood, some do not (antigenantibody reaction)
• antigen- introduced into blood
A
• antibody- substance that acts
to neutralize a specific antigen
Family # 1
A X AB
Blood Group of
Child Taken
Home
O
O X O
?
?
A
B
O
AB
?
?
A, O
?
?
A,B,
AB,
O
?
A,O
A,B,
AB
?
?
A,B
AB
?
B,O
B,O
?
?
A,B,
AB
?
A,O
B,O
O
A,B
O
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Baker High School
AB
Family # 2
?
?
B
Parental Blood
Group
?
B
21
A,B,
AB
A,B,
AB
A,B
A,B
AB
Genes, Alleles, and Chromosomes
Mendel’s
Monohybrid Cross –
P to F1
A Punnett square,
something we’ll cover
in a moment.
Staying the Course –
Mendel Continued
Crosses to the F2 (the
grandchildren)
What was learned?
The green trait was not lost or
altered, even though it
disappeared in the F1.
One trait is dominant to the
other in its expression.
The reappearance of the recessive trait in ¼ of the F2, suggests genes
come in pairs that separate in the formation of sex cells.
Monohybrid Crosses and the Principle of Segregation
A cross between individuals differing in single
character is a monohybrid cross.
Principle of Segregation ....
Genes come in pairs that
separate in the formation of
sex cells (and these sex cells
unite randomly at fertilization).
Dihybrid Crosses:
P1: Smooth / Yellow (homozygous
for both)
P2 Wrinkled / Green
(homozygous for both)
F1 Generation
(heterozygous for both)
Are Different Characters Like Color
and Shape
Mendel performed dihybrid crosses
to find out.
Mendel’s conclusion: Different
characters are inherited independently,
called:
(37)
Independent Assortment
F2 generation of a Dihybrid cross that
demonstrates:
(38)
Independent Assortment
always produces a:
(39)
9 : 3 : 3
1
Phenotypic ratio
Dihybrid Cross:
28
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The human ABO blood
group illustrates another
genetic phenomenon –
Codominance
(40)________________
Codominance occurs
when the phenotype
associated with each
allele is expressed in the
heterozygote. The AB phenotype
(genotype IA IB) is
an example of
codominance
Incomplete & Codominance
CODOMINANCE
In cattle, the allele for red hair is
codominant with the allele for
white hair. The offspring has a
(38)__________ of red and
white hair and looks pinkish /
brown from a distance.
In some chickens black feather
are (39) ______________ with
white, the heterozygous
offspring appear speckled.
CODOMINANCE
* (40)____ __________
CONTRIBUTE TO THE
PHENOTYPE OF THE
ORGANISM
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30 10
Chapter
Homozygous recessive Problems
Problem: A white mouse whose parents are both white
produces only brown offspring when mated with a brown
mouse. The white mouse is a homozygous recessive.
Explain why?
A homozygous recessive (aa) for a particular trait is mated with
a parent with a dominant phenotype (AA or Aa)
• The result will have the phenotype of the dominant parent in
the first generation.
•Problem:
In chickens, rose comb (R) is dominant to single comb (r). A
homozygous rose-combed rooster is mated with a singlecombed hen. All of the chicks in the F 1 generation were kept
together as a group for several years. They were allowed to
mate only within their own group. What is the expected
phenotype of the F2 chicks.
31
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Incomplete Dominance
INCOMPLETE DOMINANCE
Some alleles are neither
Dominant
(41)______________
Recessive
nor (42)____________
called
Incomplete
(43)______________
Dominance
A cross between four o'clock plants: F1 generation (red) RR X (white)
ww produces Rw that are neither red or white but (pink). Neither allele
is dominant.
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32 10
Chapter
Incomplete dominance in carnations
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33 10
Chapter
Genotype: All heterozygous
Phenotype: All pink
r
r
R
Rr
Rr
R
Rr
Rr
Incomplete
Dominance
F1
GENERATION
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Incomplete
Dominance
F2 GENERATION
Rr X Rr
r
R
R
r
RR
Rr
Genotype: 1 : 2 : 1
Phenotype: 1 Red : 2 Pink : 1 White
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Rr
rr
Punnett Square Problems
1.
The ability to roll the tongue is dominant over the inability to do
so in humans.
a. If two heterozygous tongue-rollers have children, what
genotypes and phenotypes could their children have?
T
T
t
t
TT
Tt
Tt
tt
b. If a non-tongue-roller has children with homozygous tongueroller, what will their children’s genotype and phenotype be?
t
t
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T
T
Tt
Tt
Tt
Tt
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Punnett Square Problems
2.
In an alien species, eye colors can be black, white or gray. The whiteeyed mother and a black-eyed father have all gray-eyed children.
a. What genotypic pattern is most likely demonstrated here?
_______________________________
INCOMPLETE DOMINANCE
b. A gray-eyed couple has two babies:
one white-eyed and one black-eyed. Does
this confirm or deny your answer to part A.
If necessary, revise your hypothesis.
c. A gray-eyed alien and her black-eyed husband want a white-eyed
baby. Is this possible? Why or why not?
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Sex Chromosomes
Sex Chromosomes determine the sex of
(44)_____________________
the offspring (XX = (45)_________,
female
male
XY = (46)_____________)
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38 10
Pedigree
____________ analysis:
A graphic representation of genetic inheritance.
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Genetic Inheritance in Humans
40
Large families provide excellent case studies of human
genetics
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• DNA fingerprinting
cystic fibrosis
Insulin
color blindness
Growth Hormone
phenylketonuria
Hemophilia Tay-Sachs disease sickle cell anemia
Down’s syndrome
Technology has made significant contributions to society, especially in the
areas of agriculture and medicine. The process of manipulating genes for
practical purposes is called genetic engineering. Most of the cells in a human
contain two copies of each of 22 different chromosomes. In addition, there is a
pair of chromosomes that determines sex: a female contains two X
chromosomes and a male contains one X and one Y chromosome.
Transmission of genetic information to offspring occurs through egg and sperm
cells that contain only one representative from each chromosome pair. An egg
and a sperm unite to form a new individual. The fact that the human body is
formed from cells that contain two copies of each chromosome--and therefore
two copies of each gene--explains many features of human heredity, such as
how variations that are hidden in one generation can be expressed in the next.
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42
Inheritance of Blood Type
Problem:
What are the results
of a heterozygous
blood type A mom
( IA i) and a
heterozygous B father
(IB i)?
AB
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B
A
O
43
Problems:
• Blood type in humans is controlled by three alleles, designated
as IA , IB (both dominant alleles), an i (recessive allele).
Genotypes for each of the four possible blood types are shown
in the table.
Blood Type
Genotype(s)
A man with blood type A, whose
Mother has type O, has a child
With a woman that has type AB
Blood. Which blood types are possible
in their children?
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A
IA IA or IA i
B
I B I B or I B i
AB
I A IB
O
ii
44
Problems:
• Egyptian Mau cats are genetically crossed for
certain lengths of fur. A breeder knows that short
hair is dominant over long hair. If 75% of the
kittens are born with short hair, what are the
parents’ MOST LIKELY genotypes?
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45
Problems:
• In rabbits, black hair is dominant to brown. If a
heterozygous black-haired rabbit and a brownhaired rabbit were crossed, what percentage of
their offspring would be brown-haired?
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46
Problems:
• Which genetic cross will produce all heterozygous
offspring?
A. RR x rr
B. rr x rr
C. RR x RR
D. Rr x R r
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Problems:
• Brown eyes are dominant to blue eyes, and dark hair is dominant to
blond hair. A woman is heterozygous for brown eyes and dark hair. A
man is also heterozygous for both traits. What is the chance that their
child will have blue eyes and blond hair?
• Homozygous Brown eyes = BB; Heterozygous Brown eyes = Bb
• Homozygous Blue eyes = bb; Homozygous blond hair = dd
Woman: Bb Dd X Man: Bb Dd
BD
Bd
bD
bd
BD
BBDD
BBDd
BbDD
BbDd
Bd
BBDd
BBdd
BbDd
Bbdd
bD
BbDD
BbDd
bbDD
bbDd
bd
BbDd
BBdd
bbDd
bbdd
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48
Problems:
• Brown eyes are dominant to blue eyes, and dark hair is dominant to
blond hair. A woman is heterozygous for brown eyes and dark hair. A
man is also heterozygous for both traits. What is the chance that their
child will have blue eyes and blond hair?
• Homozygous Brown eyes = BB; Heterozygous Brown eyes = Bb
• Homozygous Blue eyes = bb; Homozygous blond hair = dd
Woman: Bb Dd X Man: Bb Dd
Blue eyes and blond hair
has a genotype
Bd
bD
bd
BD
of [bb dd]
BD
BBDD
BBDd
BbDD
BbDd
Bd
BBDd
BBdd
BbDd
Bbdd
bD
BbDD
BbDd
bbDD
bbDd
bd
BbDd
BBdd
bbDd
bbdd
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• Since both the father and mother are heterozygous for two traits, hair color
and eye color, what is the phonotypical ratio for the offspring?
9
:
Brown Hair Brown Eyes
3
:
Brown Hair
Blue Eyes
3
:
Blond Hair
Brown Eyes
1
:
Blond Hair
Blue Eyes
BD
Bd
bD
bd
BD
BBDD
BBDd
BbDD
BbDd
Bd
BBDd
BBdd
BbDd
Bbdd
bD
BbDD
BbDd
bbDD
bbDd
bd
BbDd
BBdd
bbDd
bbdd
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50
Problems:
• In pea plants, the allele for round seeds is dominant over wrinkled
seeds. Plant 1 has round seeds, and plant 2 has wrinkled seeds.
When these plants are crossed, 50% of their offspring have round
seeds and 50% have wrinkled seeds. What are the parent genotype?
Two possibilities!
• Round: RR, Rr
• Wrinkled: rr
R
R
r
Rr
Rr
r
Rr
Rr
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R
r
r
Rr
rr
r
Rr
rr
51
Problems:
• In lions, white color is a recessive trait, and color brown is
dominant. If a white lion mates with a homozygous
brown lion, approximately what percentage of their
offspring would be white?
•
Brown: BB, Bb White: bb
B
B
b
Bb
Bb
b
Bb
Bb
0%.........no white lions!
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Problems:
Study the figure below. Which statement is the most reasonable explanation of
these experimental results?
a.
One parental plant was homozygous for dark flower color, and the other
was homozygous for light flower color
b. One parental plant was heterozygous, and other was homozygous for dark
flower color.
c.
Both parents plants were homozygous for dark flower color.
d. Both parental plants were heterozygous.
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53
Problems:
• Gray fur (B) in mice is dominant over white
fur (b). Two mice that are homozygous for
white fur color are crossbred. If they have
a total of 334 offspring, approximately how
many can be expected to have gray fur?
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54
Problems:
• Which genotype is heterozygous for two
traits?
a. ggTt
b. GgTt
c. GgTT
d. GGTT
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55
Problems:
• In gerbils, brown fur is dominant to black fur. Which
Punnett square shows a cross between one brown-furred
gerbil and one black-furred gerbil that could produce
offspring with black fur?
• BB = brown, Bb = brown, bb = black
B
b
b
Bb
bb
b
Bb
bb
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Problems:
In a certain squirrel population, a black fur gene is dominant
to a gray fur gene. Which genotypes show a cross
between a homozygous black-furred squirrel and a
homozygous gray-furred squirrel?
BB = Black, Bb = Black bb = gray
A.
B.
C.
D.
GG
Gg
GG
Gg
x
x
x
x
gg
Gg
GG
gg
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Application of Genetics and DNA
• DNA fingerprinting: (video)
• Genetic Disorders: Most genetic disorders are caused by
____________ alleles.
• cystic fibrosis, Insulin, color blindness, phenylketonuria –
lacks enzyme to proce protein (PKU test), Hemophilia, TaySachs disease, sickle cell anemia, Down’s syndrome.
(video)
• _______________________: a lethal genetic disorder
caused by a rare ______________ allele.
• _____________________: Human traits that are carried
on the X Chromosome (most of them)…______________,
an X-Linked disorder
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Hemophilia A
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Great links to practice!!
• http://anthro.palomar.edu/mendel/quizzes/mendqui
2.htm (yeuozt)
• http://library.thinkquest.org/C004367/be1.shtml
(yftlnr)
• http://www.cellsproject.org/examples/sc/page22.ht
ml (ymdrvm)
• http://biology.clc.uc.edu/courses/bio105/geneprob.
htm (36r6f)
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• Week 6 & 7 Chapter 10
• Mendelian Genetics, Punnett Square
• Pedigree, Genetic Diseases, Genetic Tech
• Baker Academy Biology
DNA & RNA: Structure and Functions 11.1 – 11.3
The Need for Energy
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