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Lesson
3
Heredity and Genetics
Family members often share a strong physical
resemblance.
What inherited characteristics are visible in this family?
Lesson
3
Lesson Objectives
In this lesson, you will learn to:
• Examine genetics and its role in fetal development
• Identify common genetic disorders
• Analyze genetic research and technology and their
impact on the health of people with genetic disorders
Lesson
3
Heredity
Inheriting Traits
• No two individuals are exactly alike. Even identical twins
have some differences.
• Heredity is a significant factor that influences the way an
individual develops.
• Some traits that you inherit from your parents are your eye
and hair color.
• Environment can also influence inherited traits.
Lesson
3
Heredity
Chromosomes and Genes
• Most cells of your body contain a nucleus—the cell’s control
center.
• Inside each nucleus is a set of chromosomes.
• Most cells in the body contain 46 chromosomes arranged as
23 pairs.
• Sections of chromosomes, called genes, carry codes for
specific traits.
• Like chromosomes, genes occur in pairs. One gene from each
pair is inherited from each parent.
Lesson
3
DNA
• All living things are made of DNA.
• Chemical compounds, called bases,
make up the structure of DNA.
• The order of the bases is called the
genetic code. Cells use the genetic
code to make proteins.
• Unless you have an identical twin,
your DNA is different from that of
any other person.
Heredity
Lesson
3
Genetics and Fetal Development
Dominant and Recessive Genes
• At least one pair of genes is responsible for each human
trait.
• Some genes are dominant, and others are recessive. The
traits of dominant genes generally appear in offspring
whenever they are present.
• The traits of recessive genes usually appear only when
dominant genes are not present.
Lesson
3
Genetics and Fetal Development
Genes and Gender
• In humans, one pair of
chromosomes determines the
gender of an individual.
• If you are female, these two
chromosomes look exactly alike and
are called X chromosomes.
• If you are male, the two
chromosomes differ—one is shorter
than the other and is called a Y
chromosome.
Lesson
3
Genetics and Fetal Development
Genetic Makeup
• Sperm contain an X or a Y chromosome. Eggs have only an
X chromosome.
• The gender of a child is determined by which type of
sperm—X or Y—unites with an egg.
Lesson
3
Genetic Disorders
Mutation
• Sometimes the genes that an individual inherits contain a
mutation, or abnormality, in the base sequence of the
genetic code.
• Often the mutation has little or no effect on the individual,
but sometimes the mutation can result in defects or other
health problems.
• Some genetic disorders, such as those that cause birth
defects, are apparent right away.
Lesson
3
Common Human Genetic Disorders
Genetic Disorders
Lesson
3
Genetic Disorders
Test for Genetic Disorders
Two common technologies used to test for genetic
disorders are:
1. Amniocentesis
2. Chorionic villi sampling (CVS)
Lesson
3
Genetic Disorders
Genetic Counseling
• Research for diagnosing, preventing, and treating
genetically related diseases has resulted in a wide variety of
programs.
• Genetic counselors can advise families about the probability
of having a child with a genetically related disease.
• They also can guide families of children with genetic
disorders about possible treatment options.
Lesson
3
Genetic Research to Cure Disease
Gene Therapy
• When the defective gene is replaced with a normal one using
the gene therapy, the cells with the new gene begin to make
the missing substance.
• The practice of placing fragments of DNA from one organism
into another is called genetic engineering, and it is
considered highly experimental.
• Genetic diseases for which scientists are researching gene
therapies include cystic fibrosis and various types of cancer.
Lesson
3
Genetic Research to Cure Disease
Genetically Engineered Drugs
• Genes used to treat disease aren’t usually inserted directly
into human beings.
• Instead they are placed into other organisms, causing them
to produce substances that can be used to treat human
diseases and disorders.
• Genetically produced medicines include treatments for burns
and ulcers, growth defects, and ovarian and breast cancers.
• Factor VIII medicines treat hemophilia. Genetic engineering
also is used to produce some vaccines that prevent
diseases.
Lesson
3
Quick Review
Choose the appropriate option.
Q. The passing of traits from
parents to their children is
called _________.
1. heredity
2. DNA
3. genes
4. genetic disorder
Lesson
3
Quick Review - Answer
A. 1. heredity
The passing of traits from parents to their children is
called heredity.
Click Next to attempt another question.
Lesson
3
Quick Review
Choose the appropriate option.
Q. Which of the following is not a
genetic disorder?
1. Sickle-cell anemia
2. Cirrhosis
3. Cystic fibrosis
4. Tay-Sachs disease
Lesson
3
Quick Review - Answer
A. 2. cirrhosis
Genetic disorders do not include cirrhosis.
Click Next to attempt another question.
Lesson
3
Quick Review
Choose the appropriate option.
Q. Amniocentesis is a procedure
in which a syringe is inserted
through a pregnant female’s
abdominal wall and into the
amniotic fluid surrounding the
developing fetus.
True
False
Lesson
3
Quick Review - Answer
A. True. Amniocentesis is a procedure in which a syringe is
inserted through a pregnant female’s abdominal wall and
into the amniotic fluid surrounding the developing fetus.
Click Next to attempt another question.
Lesson
3
Quick Review
Choose the appropriate option.
Q. Fetal development is the making
of a new and unique human
being. Genetics play only a
marginal role in the
development of the fetus.
True
False
Lesson
3
Quick Review - Answer
A. False. Fetal development is the making of a new and
unique human being. Genetics play an important role in
the development of the fetus.
Click Next to attempt another question.
Lesson
3
End of Lesson 3
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Lesson
Quick Review - Answer
3
A. Correct! The passing of traits from parents to their
children is called heredity.
Click Next to attempt another question.
Lesson
3
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Lesson
3
Heredity
Inheriting Traits
• No two individuals are exactly alike. Even identical twins
have some differences.
• Heredity is a significant factor that influences the way an
individual develops.
Heredity
theinherit from your parents are your eye
• Some traits
that is
you
passing
of traits
and
hair color.
that are biological
from parents
• Environment
cantoalso influence inherited traits.
their children.
Lesson
3
Heredity
Chromosomes and Genes
• Most cells of your body contain a nucleus—the cell’s control
center.
• Inside each nucleus is a set of chromosomes.
A chromosome is
• Most acells
in the body
contain 46 chromosomes arranged as
threadlike
structure
23 pairs.
found within the
nucleus of a cell that
• Sections of chromosomes, called genes, carry codes for
carries the code for
specific traits.
inherited traits.
• Like chromosomes, genes occur in pairs. One gene from each
pair is inherited from each parent.
Lesson
3
Heredity
Chromosomes and Genes
• Most cells of your body contain a nucleus—the cell’s control
center.
• Inside each nucleus is a set of chromosomes. A gene
is the basic
• Most cells in the body contain 46 chromosomes
unit of arranged as
23 pairs.
heredity.
• Sections of chromosomes, called genes, carry codes for
specific traits.
• Like chromosomes, genes occur in pairs. One gene from each
pair is inherited from each parent.
Lesson
3
DNA
• All living things are made of DNA.
• Chemical compounds, called bases,
DNA,
or
make up the structure
of DNA.
deoxyribonucleic
is the
chemical
• The order of theacid,
bases
is called
the
unit use
thatthe
makes
up
genetic code. Cells
genetic
chromosomes.
code to make proteins.
• Unless you have an identical twin,
your DNA is different from that of
any other person.
Heredity
Lesson
3
Genetic Disorders
Mutation
• Sometimes the genes that an individual inherits contain a
A genetic
mutation, or abnormality, in the base sequence of the
disorder is a
genetic code.
disorder caused
partly or
• Often the mutation has little or no effect on the individual,
completely by a
but sometimes the mutation can result in defects or other
defect in genes.
health problems.
• Some genetic disorders, such as those that cause birth
defects, are apparent right away.
Lesson
3
Genetic Disorders
Test for Genetic Disorders
Two common technologies used to test for genetic
disorders are:
1. Amniocentesis
2. Chorionic villi sampling
(CVS)
Amniocentesis
is a
procedure in which a
syringe is inserted through
a pregnant female’s
abdominal wall into the
amniotic fluid surrounding
the developing fetus.
Lesson
3
Test for Genetic Disorders
Genetic Disorders
Chorionic villi
(CVS) is a
Two common technologies used tosampling
test for genetic
procedure in which a small
disorders are:
piece of membrane is
removed from the chorion,
1. Amniocentesis
a layer of tissue that
develops into the placenta.
2. Chorionic villi sampling (CVS)
Lesson
3
Genetic Research to Cure Disease
Gene Therapy
• When the defective gene is replaced with a normal one using
the gene therapy, the cells with the new gene begin to make
the missing substance.
Gene therapy
• The practice of placing
fragments of DNA from one organism
is the
process
of engineering, and it is
into another
is called
genetic
normal
consideredinserting
highly experimental.
genes into human
• Genetic diseases
which scientists are researching gene
cells tofor
correct
therapies include
fibrosis and various types of cancer.
geneticcystic
disorders.
Lesson
3
Quick Review - Answer
A. Correct! Genetic disorders do not include the following:
cirrhosis.
Click Next to attempt another question.
Lesson
3
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Lesson
3
Quick Review - Answer
A. Correct! Amniocentesis is a procedure in which a
syringe is inserted through a pregnant female’s
abdominal wall and into the amniotic fluid surrounding
the developing fetus.
Click Next to attempt another question.
Lesson
3
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Lesson
3
Quick Review - Answer
A. Correct! Fetal development is the making of a new and
unique human being. Genetics play an important role in
the development of the fetus.
Click Next to attempt another question.
Lesson
3
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.