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Karyotype
Autosome
centromere
Sex
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Section:
Chromosomes
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Section:
Figure 14-3 A Pedigree
Section 14-1
A circle represents
a female.
A horizontal line connecting
a male and female
represents a marriage.
A half-shaded circle
or square indicates
that a person is a
carrier of the trait.
A completely
shaded circle or
square indicates
that a person
expresses the
trait.
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Section:
A square represents
a male.
A vertical line and a
bracket connect the
parents to their children.
A circle or square
that is not shaded
indicates that a
person neither
expresses the trait
nor is a carrier of
the trait.
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Section:
Genotype
SS
Ss
Phenotype
Normal Hemoglobin
Sickle Cell Trait
ss
Sickle Cell Anemia
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Comments
Normal Blood
Sickles under low O2
Can survive malaria
Usually dies
Protein becomes less soluble and
sticky
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Section:
For example, sickle-cell disease is caused by a mutation of a single base pair
substitution in the gene that codes for one of the polypeptides of hemoglobin.
– A change in a single nucleotide from T to A in the DNA template leads to
an abnormal protein.
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Section:
Fig. 17.23
Figure 14-8 The Cause of Cystic Fibrosis
Section 14-1
Chromosome
#7
CFTR
gene
deletion
The most common allele
that causes cystic fibrosis is
missing 3 DNA bases. As
a result, the amino acid
phenylalanine is missing
from the CFTR protein.
Protein misfolds and
makes the protein
channel nonfunctional
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Normal CFTR is a chloride
ion channel in cell
membranes. Abnormal
CFTR cannot be transported
to the cell membrane.
The cells in the person’s airways
are unable to transport chloride
ions. As a result, the airways
become clogged with a thick
mucus.
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Tay Sachs
Lipid builds up in brain,
Mental retardation.
Blindness.
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Achondroplasia
A type of dwarfism
caused by a
dominant allele
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Concept Map
Section 14-1
Autosomol
Disorders
caused by
Recessive
alleles
Dominant alleles
Codominant
alleles
include
include
include
Huntington’s
disease
Sickle cell
disease
Galactosemia
Albinism
Cystic
fibrosis
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Section:
Phenylketonuria
Tay-Sachs
disease
Achondroplasia
Hypercholesterolemia
Figure 14-4 Blood Groups
Section 14-1
Phenotype
(Blood Type
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Section:
Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
Interest Grabber
Section 14-2
Gender Benders
You may remember that in humans, the sperm cells may carry an X
chromosome or a Y chromosome, while egg cells have only X
chromosomes. Sometimes, errors during meiosis in one of the parents
produce offspring with an abnormal number of sex chromosomes.
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Section:
Interest Grabber continued
Section 14-2
1. On a sheet of paper, construct a Punnett square for the following cross:
XX x XY. Fill in the Punnett square. What does the Punnett square
represent? According to the Punnett square, what percentage of the
offspring from this genetic cross will be males? What percentage will be
females?
2. On a sheet of paper, construct a Punnett square for the following cross:
XXX x XY. Fill in the Punnett square. How is this Punnett square
different from the first one you constructed? What might have caused
this difference?
3. How do the offspring in the two Punnett squares differ?
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Section:
Section Outline
Section 14-2
14–2
Human Chromosomes
A. Human Genes and Chromosomes
B. Sex-Linked Genes
1. Colorblindness
2. Hemophilia
3. Duchenne Muscular Dystrophy
C. X-Chromosome Inactivation
D. Chromosomal Disorders
1. Down Syndrome
2. Sex Chromosome Disorders
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Section:
Males
determine
the sex half the
sperm
have an X
and the
other half
has a Y
Sex Linked Gene= a gene
on the X sex chromosome
Genotype
Phenotype
XRXR
Red ♀
XRXr
Red ♀
XrXr
XRY
Xr Y
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Section:
XR
Y
Xr
XRXr
XrY
Xr
XRXr
XrY
White ♀
Red ♂
White ♂
F1 Genotypic ratio= 2:2
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1. What are the
possible genotypes
for eye color of a
female fruit fly? Of
a male?
Female; XRXR, XRXr,
or XrXr; male: XRY
or XrY
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Section:
2. Construct a cross
that could produce a
white-eyed female
fruit fly.
Students should
show a cross
between a whiteeyed male (XrY) and
a heterozygous
female (XRXr) or a
homozygous
recessive female
(XrXr). Homozygous
recessive female
offspring (XrXr) will
have white eyes.
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Section:
Males
determine
the sex half the
sperm
have an X
and the
other half
has a Y
Sex Linked Gene= a gene
on the X sex chromosome
Genotype
Phenotype
XRXR
Red ♀
XRXr
Red ♀
XrXr
XRY
Xr Y
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Xr
Y
XR
XRXr
XRY
Xr
Xr Xr
XrY
White ♀
Red ♂
White ♂
F2 Genotypic ratio= 1:1:1:1
Colorblindness
is a sex-linked
recessive trait
.
Make a Genotype/Phenotype chart for
colorblindness.
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Section:
Carrier – a
normal
female with a
sex linked
recessive
trait
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Genotype
Phenotype
XCXC
Normal ♀
XCXc
Normal ♀
(carrier)
XcXc
Color Blind ♀
XCY
Normal ♂
XcY
Color Blind ♂
Genotype
H H
X X
H h
X X
h h
X X
H
XY
h
XY
Phenotype
Normal ♀
Normal ♀(Carrier)
Hemophiliac ♀
Normal ♂
Hemophiliac ♂
Carrier= A normal female with a sex
linked recessive gene.
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Section:
Genotype
Phenotype
XRXR
Normal ♀
XRXr
Normal ♀
XrXr
Color Blind
♀
Normal ♂
XRY
XrY
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Section:
Color Blind
♂
Figure 15.11 X
Two cell populations
in adult
inactivation
andcat:
the tortoiseshell
Active X
Early embryo:
Orange
fur
X chromosomes
Cell division
Inactive X
and X
chromosome Inactive X
inactivation
Black
fur
Allele for
orange fur
Allele for
black fur
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Active X
cat
Genotype
XBXB
XBXb
b b
XX
B
X Y
XbY
Sex Linked Gene
-A Gene on the
X Sex
Chromosome
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Section:
Phenotype
Yellow Female
Tortoise Shell Female
Black Female
Yellow Male
Black Male
Figure 14-13 Colorblindness
Section 14-2
Father
(normal vision)
Colorblind
Normal
vision
Male
Female
Daughter
(normal vision)
Son
(normal vision)
Daughter
(carrier)
Son
(colorblind)
Mother
(carrier)
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Section:
Figure 14-13 Colorblindness
Section 14-2
Father
(normal vision)
Colorblind
Normal
vision
Male
Female
Daughter
(normal vision)
Son
(normal vision)
Daughter
(carrier)
Son
(colorblind)
Mother
(carrier)
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1. Describe how
nondisjunction in
meiosis I and in
meiosis II differ.
Meiosis I:
homologous
chromosomes fail to
separate; meiosis II:
sister chromatids
fail to separate.
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Section:
2. How is it possible for
nondisjunction to
occur and for some
normal gametes to
be produced?
If nondisjunction
occurs in meiosis II,
two of the four
resulting gametes
will be normal
haploid.
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Section:
Trisomy 21
Down’s Syndrome
Trisomy 18
Trisomy 15
Edward’s Syndrome
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Section:
XY
XY
O
Aneuploidy
X
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Nondisjunction
of the sex
chromosomes
can result in
XXY and XO
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Section:
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XXY-Klinefelter’s
Syndrome
Section:
XO=Turner’s Syndrome
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Section:
Interest Grabber
Section 14-3
Bioethics and You
As you become more aware of scientific advances in genetics, you might
realize that with the ability to manipulate genes, there comes responsibility.
This ability provides an opportunity to improve the lives of many people.
But there is also a potential for errors or intentional misuse of the
technology.
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Section:
Interest Grabber continued
Section 14-3
Working with a partner, answer the following questions.
1. In what type of situation do you think genetic engineering—changing
the genes of organisms—is warranted? Explain your reasoning about
your position. If you do not think that genetic engineering is ever
warranted, explain your reasons for your position.
2. In what type of situation do you think genetic engineering might be
misused? Suggest limits that might be placed on the manipulation of
genes to avoid its misuse.
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Section:
Section Outline
Section 14-3
14–3
Human Molecular Genetics
A. Human DNA Analysis
1. Testing for Alleles
2. DNA Fingerprinting
B. The Human Genome Project
1. Rapid Sequencing
2. Searching for Genes
3. A Breakthrough for Everyone
C. Gene Therapy
D. Ethical Issues in Human Genetics
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Restriction enzymes can only
fit the DNA at a specific base
sequence EX: CTTAAG
Animation
Animation
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Figure 13-6 Gel Electrophoresis
Section 13-2
Power
source
DNA plus restriction
enzyme
Longer
fragments
Shorter
fragments
Mixture of DNA
fragments
Gel
http://learn.genetics.utah.edu/units/biotech/gel/
Gel Electrophoresis simulation
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Section:
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Section:
P 373
Differences in DNA sequences on homologous
chromosomes result in different restriction fragment
length patterns RFLP
- these may be sorted by length using gel
electrophoresis
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Section:
Presence of black bars
indicates the target gene is in
the sample
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Section:
Using dyes or radioactive DNA probes can
determine the presence of particular sections
DNA in a sample
– DNA fingerprint
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Section:
Different people have
different DNA
-DNA when cut by
enzymes will leave
different size fragments
-which will separate into
different electrophoresis
patterns
-a DNA fingerprint
If there is only a small sample of
DNA available- more copies can be
made by PCR -polymerase chain
reaction (p371)
Link to DNA
Fingerprint Lab
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Section:
Figure 14-18 DNA Fingerprinting
Section 14-3
Restriction enzyme
Chromosomes contain large
amounts of DNA called repeats
that do not code for proteins.
This DNA varies from person to
person. Here, one sample has
12 repeats between genes A
and B, while the second
sample has 9 repeats.
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Section:
Restriction enzymes are used
to cut the DNA into fragments
containing genes and repeats.
Note that the repeat fragments
from these two samples are of
different lengths.
The DNA fragments are
separated according to size using
gel electrophoresis. The
fragments containing repeats are
then labeled using radioactive
probes. This produces a series of
bands—the DNA fingerprint.
Figure 13-7 DNA Sequencing
Section 13-2
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Section:
DNA sequencing notebook
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Single stranded cDNA is made from a
target cell’s active mRNA and tagged
with a fluorescent dye
DNA Microarray
Identifies Active Genes
A DNA Chip is a microarray of many
spots where single stranded DNA is
attached – each strand representing a
different gene.
If a gene is active the dye labeled cDNA will attach and cause that spot to light up when a
laser strikes it. This tells you which genes are active.
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Section:
Figure 14-21 Gene Therapy
Section 14-3
Bone
marrow cell
Normal hemoglobin gene
Nucleus
Chromosomes
Genetically engineered virus
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Bone
marrow
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Videos
Click a hyperlink to choose a video.
Human Sex Determination
Nondisjunction
Point Mutation
Video 1
Human Sex Determination
Click the image to play the video segment.
Video 2
Nondisjunction
Click the image to play the video segment.
Video 3
Point Mutations
Click the image to play the video segment.
Go Online
Links from the authors on DNA samples
Career links on geneticists
More information on the Human Genome Project
Interactive test
For links on pedigrees, go to www.SciLinks.org and enter the Web
Code as follows: cbn-4141.
Interest Grabber Answers
1. This pedigree shows the inheritance of attached ear lobes. Which parent
has attached ear lobes?
The father
2. How many children do the parents have? Which child has attached ear
lobes?
Three; the daughter has attached ear lobes.
3. Which child is married? Does this child’s spouse have attached ear lobes?
Do any of this child’s children have attached ear lobes?
The second son; no; yes, the daughter
Interest Grabber Answers
1. On a sheet of paper, construct a Punnett square for the following cross:
XX x XY. Fill in the Punnett square. What does the Punnett square
represent? According to the Punnett square, what percentage of the offspring
from this genetic cross will be males? What percentage will be females?
One half of the offspring will be males; the other half, females.
2. On a sheet of paper, construct a Punnett square for the following cross: XXX
x XY. Fill in the Punnett square. How is this Punnett square different from the
first one you constructed? What might have caused this difference?
One of the gametes has two X chromosomes instead of just one. This might
have resulted from a mistake in meiosis: Instead of separating, the pair of X
chromosomes stayed together.
3. How do the offspring in the two Punnett squares differ?
Instead of two XX and two XY offspring, there are one XX and one XY (which
are normal), plus one XXX and one XXY (which are abnormal).
Interest Grabber Answers
1. In what type of situation do you think genetic engineering—changing the
genes of organisms—is warranted? Explain your reasoning about your
position. If you do not think that genetic engineering is ever warranted,
explain your reasons for your position.
Students’ answers likely will include medicinal uses of genetic engineering,
such as gene therapy for genetic diseases and production of needed
substances such as insulin. Some students may object to all genetic
manipulations.
2. In what type of situation do you think genetic engineering might be
misused? Suggest limits that might be placed on the manipulation of genes
to avoid its misuse.
Students’ answers may include the “designing” of human babies with
desirable traits and the cloning of humans. Some students may object to
genetically altered foods.
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