Transcript Chapter 14 Human Genome

Interest Grabber
Section 14-1
A Family Tree
To understand how traits are passed on from generation to generation, a
pedigree, or a diagram that shows the relationships within a family, is used.
In a pedigree, a circle represents a female, and a square represents a
male. A filled-in circle or square shows that the individual has the trait being
studied. The horizontal line that connects a circle and a square represents
a marriage. The vertical line(s) and brackets below that line show the
child(ren) of that couple.
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Interest Grabber continued
Section 14-1
1. This pedigree shows the inheritance of attached ear lobes. Which
parent has attached ear lobes?
2. How many children do the parents have? Which child 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?
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Section Outline
Section 14-1
14–1
Human Heredity
A. Human Chromosomes
B. Human Traits
C. Human Genes
1. Blood Group Genes
2. Recessive Alleles
3. Dominant Alleles
4. Codominant Alleles
D. From Gene to Molecule
1. Cystic Fibrosis
2. Sickle Cell Disease
3. Dominant or Recessive?
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Concept Map
Section 14-1
Autosomal
Disorders
caused by
Dominant alleles
Codominant
alleles
include
include
include
Huntington’s
disease
Sickle cell
disease
Galactosemia
Albinism
Cystic
fibrosis
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Recessive
alleles
Phenylketonuria
Tay-Sachs
disease
Achondroplasia
Hypercholesterolemia
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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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.
Figure 14-4 Blood Groups
Section 14-1
Phenotype
(Blood Type
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Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
Figure 14-8 The Cause of Cystic Fibrosis
Section 14-1
Chromosome
#7
CFTR
gene
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.
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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.
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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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 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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Nondisjunction
Section 14-2
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
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Meiosis II
Nondisjunction
Section 14-2
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
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Meiosis II
Nondisjunction
Section 14-2
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
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Meiosis II
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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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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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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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 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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Locating Genes
Section 14-3
Gene
Sequence
Promoter
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Start
signal
Gene
Stop
signal
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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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 14-21 Gene Therapy
Section 14-3
Bone
marrow cell
Normal hemoglobin gene
Nucleus
Chromosomes
Genetically engineered virus
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Bone
marrow