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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’ll learn to:
Explain the significance of genetics and its role in fetal
development.
Identify common genetic disorders.
Explain how genetic research and technology has impacted
the health status of families and individuals 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
Heredity
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.
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
Genetic Disorders
Common Human 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. The passing of traits from parents to their children is called
heredity.
Click Next to attempt another question.
Lesson 3
Quick Review
Provide a short answer to the question given below.
Q. Name three human genetic disorders.
Click Next to view the answer.
Lesson 3
Quick Review - Answer
A. Some human genetic disorders are:
Sickle-cell anemia
Tay-Sachs disease
Cystic fibrosis
Down syndrome
Hemophilia
Phenylketonuria (PKU)
Click Next to attempt another question.
Lesson 3
Quick Review
Provide a short answer to the question given below.
Q. Explain the difference between amniocentesis and chorionic
villi sampling (CVS).
Click Next to view the answer.
Lesson 3
Quick Review - Answer
A. 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.
Chorionic villi sampling (CVS) is a procedure in which a
small piece of membrane is removed from the chorion, a
layer of tissue that develops into the placenta.
Click Next to attempt another question.
Lesson 3
Quick Review
Analyze the following question.
Explain the significance of genetics and its role in fetal
development.
Lesson 3
Quick Review - Answer
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.
Thethat
passing
Some traits
you inherit from your parents are your eye and
traits from
hair of
color.
parents to their
children iscan
called
Environment
also influence inherited traits.
heredity.
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 cells
in the body
contain 46 chromosomes arranged as
a 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 ofarranged 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
Heredity
DNA
All living things are made of DNA.
Chemical compounds, called bases,
or
make up the structureDNA,
of DNA.
deoxyribonucleic
chemical
The order of the acid,
basesisisthe
called
the
unit
that
up
genetic code. Cells
use
themakes
genetic
chromosomes.
code to make proteins.
Unless you have an identical twin,
your DNA is different from that of
any other person.
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
Genetic Disorders
Test for Genetic Disorders
Chorionic villi
sampling
(CVS) is a
Two common technologies used to 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 fragments
therapy of DNA from one organism
The practice of placing
process
of engineering, and it is considered
into anotherisisthe
called
genetic
inserting normal
highly experimental.
genes into human
Genetic diseases
forcorrect
which scientists are researching gene
cells to
therapies include
cystic
fibrosis and various types of cancer.
genetic
disorders.