Mrs. Stewart

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2.1.1 - Genetic Disorders and Genetic Testing

• Mrs. Stewart
• Central Magnet School

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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.
•  

3
Family Bulletin Continued

• Mr. Smiths 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.
  Ginas brother and his wife have a five-month-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.
•  

4
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.

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Genetic Testing Pre-Survey

• Take the genetic testing survey and evaluate your
  opinion for each of the questions based on what
  you already know

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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

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What are Genetic Disorders?

• Genetic disorder - a disease caused by
  abnormalities in an individuals genetic
  material.
• Both environmental and genetic factors play a
  role in the development of disease.

8
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?

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Biology Review

• Using R can roll tongue, and r cant roll
  tongue
• Write a homozygous dominant genotype
• Write a homozygous recessive genotype
• Write a heterozygous genotype
• 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

RR
rr
Rr
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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.

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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

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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

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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.

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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.

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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

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Genetic Testing and Screening
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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

18
What is Genetic Testing?

• Genetic testing looks at genotype to determine if
  someone has a genetic disorder, will develop one,
  or is a carrier.

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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

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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.

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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 couples ethnic background
  or if there is a family history of the disease.
• Example Tay-Sachs disease or sickle cell
  disease.

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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?va5SB9t7m0Vs

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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.

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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.

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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.