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2.1.1 - Genetic Disorders and
Genetic Testing
MRS. STEWART
CENTRAL MAGNET SCHOOL
Family Bulletin
 This week, James and Judy Smith have some unexpected
news to share with their family. They just found out that
they are expecting their third child. Now that the shock
has worn off, they are excited to welcome a new member
into their family. However, since Judy is in her forties,
her pregnancy is considered high risk. The doctor has
suggested genetic testing and screening to monitor the
pregnancy and to identify any potential complications
with the fetus. James and Judy never had to make these
kinds of decisions with their first two kids. The idea of
learning too much about their child before he or she is
born is a bit scary, so they ask their doctor for more
information.
Family Bulletin Continued
 Mr. Smith’s brother Aaron and his new wife Gina are elated by
Judy and James’ news as they have decided that they are ready
to start their own family. They are both young, 28 and 26,
respectively, but they decide to see a doctor before they start
trying to conceive a child. Gina’s brother and his wife have a fivemonth-old son who has just been diagnosed with cystic fibrosis.
Gina knows the disease has a genetic component, so she wants to
learn more about her risk of passing this gene on to her child.
Her doctor assures her that simple genetic testing can identify
whether or not she and Aaron are carriers for the disease, but
Gina and Aaron have many unanswered questions. They never
thought that deciding to have a baby could be so complicated.
The doctor has suggested that Gina and Aaron discuss their case
with a genetic counselor.
Family Bulletin Continued
 The two couples, James and Judy, and Aaron and
Gina, are at different stages in their lives, but both
couples face important decisions regarding the
ability to look into our cells and test and screen DNA.
What types of things can we learn about our children
before they are even born? How much would you
want to know about your own genes? Follow the
Smith brothers as they explore the science and the
personal side of genetic testing and screening.
Genetic Testing Pre-Survey
 Take the genetic testing survey and evaluate your
opinion for each of the questions based on what you
already know
Objectives
 Evaluate the relationship between DNA codes
and the proteins produced

Understanding that changes in DNA lead to changes in
proteins, which could produce a genetic
disorder/disease.
 Analyze genetic testing results to predict phenotype
What are Genetic Disorders?
 Genetic disorder - a disease caused by
abnormalities in an individual’s genetic material.
 Both environmental and genetic factors play a
role in the development of disease.
Biology Review
 What is a genotype?
 The actual genetic makeup of an organism (the true “genes”
for a specific trait – the actual alleles)
 What is a phenotype?
 The physical expression of a trait
 R = able to roll tongue; r = not able to roll tongue
 Which one is dominant?
 Which one is recessive?
Biology Review
 Using R = can roll tongue, and r = can’t roll
tongue:
◦
◦
◦
Write a homozygous dominant genotype
Write a homozygous recessive genotype
Write a heterozygous genotype
Rr

RR
rr
Why is a heterozygous referred to as a carrier
 How many pairs of chromosomes do we have?
◦ 23
 What is the 23 pair called?
◦ Sex chromosomes
 What is an autosome?
◦ Every chromosome that is NOT a sex chromosome
Genetic Disorders
 Gene- a segment of DNA that contains instructions for
the production of a protein.
 Diseases and disorders result when a gene is mutated
resulting in a protein product that can no longer carry
out its normal job.
Scavenger Hunt
 In this course, we will consider four different types
of genetic disorders:




Single-gene
Multifactorial
Chromosomal
Mitochondrial
 Fill in your student response sheets by finding the
definitions and examples listed around the room,
matching them to the correct disorder on your notes
page.

Use the information provided to fill in your notes page
Single Gene Disorders
 Single gene disorders are caused by changes or
mutations that occur in the DNA sequence of
one gene.
 Single gene disorders are inherited in recognizable
patterns:



Autosomal dominant
Autosomal recessive
Sex linked
Multifactorial Disorders
 Multifactorial disorders are caused by a
combination of environmental factors and
mutations in multiple genes.
Development of heart disease is associated with multiple
genes, as well as lifestyle and environmental factors.
 Different genes that influence breast cancer development
have been found on chromosomes 6, 11, 13, 14, 15, 17 &
22.

 Many of the most common chronic illnesses are
multifactorial.
Chromosomal Disorders
 Humans have 46 chromosomes in their body
cells.
44 autosomes
 2 sex chromosomes

 Because chromosomes carry genetic information,
problems arise when there are missing or extra
copies of genes, or breaks, deletions or rejoinings
of chromosomes.
 Karyotypes - pictures of the paired
chromosomes of an individual

important in diagnosing chromosomal disorders.
Mitochondrial Disorders
 Mitochondria (the organelles in your cells
that convert energy) contain DNA.
 A mitochondrial disorder is caused by
mutations in nonchromosomal DNA of
mitochondria.
a
relatively rare type of genetic disorder
 Mitochondrial DNA is unique in that it is
passed solely from mother to child
Genetic Testing and Screening
Objectives
 Evaluate the relationship between DNA codes and the
proteins produced

Understanding that changes in DNA lead to changes in
proteins, which could produce a genetic disorder/disease.
 Analyze genetic testing results to predict
phenotype
What is Genetic Testing?
 Genetic testing looks at genotype to determine if
someone has a genetic disorder, will develop one,
or is a carrier.
Review Question
 A man and a woman are both carriers for sickle cell
disease, an autosomal recessive trait. What is the risk
of their having an affected child?
 S = No sickle cell; s = sickle cell disease
 Draw a punnett square to find answer
Answer
 Each parent is heterozygous for the condition and
has the genotype Ss (where “s” is the recessive
sickle cell allele). Each parent passes one allele to
the child, so there is a 25% chance that the child
will have sickle cell disease.
Carrier Screening
 Carrier screening determines whether an
individual carries a copy of an altered gene for a
particular recessive disease even though they do
not show the trait phenotypically.

Essentially this tells if a person is heterozygous for a
particular trait
 Carrier screening is often used if a particular
disease is common in a couple’s ethnic background
or if there is a family history of the disease.

Example: Tay-Sachs disease or sickle cell disease.
Preimplantation Genetic Diagnosis (PGD)
 PGD is used following in vitro fertilization to
diagnose a genetic disease or condition before
the embryo is implanted in the uterus.
A single cell is removed from an embryo and examined
for chromosome abnormalities or genetic changes.
 Parents and doctors can then choose which embryos to
implant.

 Secrets of the Sequence – Chosen Child video
 http://www.youtube.com/watch?v=a5SB9t7m0Vs
Fetal Screening/Prenatal Diagnosis
 Prenatal diagnosis allows parents to diagnose a
genetic condition in their developing fetus.
 Techniques such as amniocentesis, chorionic villi
sampling (CVS), and regular scheduled ultrasound
allow parents to monitor the health of the growing
fetus.
Newborn Screening
 The most widespread type of genetic screening,
newborn screening is used to detect genetic or
metabolic conditions for which early diagnosis
and treatment are available.
 State tests for newborns typically screen
anywhere from 4 to over 30 genetic or metabolic
disorders.

Testing protocol and mandates vary from state to state.
 The goal of newborn screening is to identify
affected newborns quickly in order to provide
quick treatment and care.
Activity 2.1.1
 In this activity, you will assume the role of a
genetic counselor and meet with clients faced with
difficult decisions regarding genetic disorders and
genetic testing.
 Your goal is to effectively explain the disease or
disorder to your clients as well as to outline
potential options for genetic testing and screening
and overall management of disease.