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Genetic Counseling
Ashley Carlson1st Year Genetic Counseling
Sarah Lawrence College Bronxville, NY
What is a Genetic Counselor? A health professional with experience
in medical genetics and counseling. Provides information and support to
families who:– have members with genetic
disorders or birth defects – may be at risk for genetic disorders
or birth defects Practices non-directive counseling
How Can I Become a Genetic Counselor?
Obtain a specialized graduate degree in Genetic Counseling
Most enter the field from a variety of disciplines including biology, genetics, nursing, psychology, public health and social work. (NSGC 1983)
Having experience in counseling is very important
How Did I Become a GC? High school – Took Chemistry, Biology I and
II, and Physical Science Undergrad – Biology, Genetics,
Developmental Bio, Chemistry, Statistics, Evolutionary Bio, Genetic Technology, etc.
Experience in a counseling-based agency – Worked in a Battered Women’s Shelter
Volunteered for two prenatal Genetic Counselors in Wilmington, NC for one year
What Made Me Decide to Become a Genetic Counselor?
Senior Exit Project– The idea came from my brother
Interviewed two genetic counselors Personal History
– Arnold-Chiari
Malformation I
Chromosomes They are the packages that contain
our genetic material – our genes All of our cells have 46 chromosomes Half (23) are inherited from each
parent Chromosomes exist in pairs (23 pairs)
Normal Appearing Female46,XX
Normal Male 46,XY
Cell Division/ReproductionMitosis Cell division All 46
chromosomes copy themselves
Both new cells have the same set of 46 chromosomes
Meiosis How egg and sperm
are formed One cell with 46
chromosomes divides twice resulting in 4 cells that each have only 23 chromosomes
Nondisjunction
Failure of paired chromosomes to separate during meiosis in Anaphase I
Leads to egg or sperm with extra or missing chromosomes
When abnormal egg/sperm is used for fertilization, the result is an aneuploid embryo
Down syndrome
Most common live born chromosome disorder
Extra 21 chromosome Prevalence: 1:800 births
– 350,000 people in USA Mental retardation
– Characteristic facial features
– Heart defects – Vision/hearing problems – Increased risk of Leukemia
and Alzheimer's
Trisomy 18 - Edwards Syndrome
Edwards Syndrome 1:8000 live births Mental deficiency Small jaw Short sternum Heart defects Malformed ears Rocker-bottom feet Characteristic
clenched fist 90% die before 1 yr
Turner Syndrome
Turner Syndrome
1:8000 live births Webbed neck Puffiness of hands
and feet No sexual maturation Broad chest and
widely spaced nipples Learning difficulties
What Are Genes? Genes are the units of heredity we
receive from our parents They are packaged at specific
locations (loci) on our chromosomes Like chromosomes, they occur in
pairs, one from each parent They are sequences of DNA
Reasons for Genetic Disease A change in a gene from its natural state Changes can be inherited or acquired Genes themselves do not cause disease Mutation = gene malfunction = malformed
or absent gene product = disease “She has the breast cancer gene…”
means she has a mutated version of that gene
ALL of us have some version of the Breast Cancer Gene or BRCA
Recessive Inheritance
Autosomal Recessive Conditions
Cystic FibrosisXeroderma PigmentosaTay-SachsSickle Cell Anemia
AlbinismEyes, hair and
skinLack of
pigment25% risk to
children of carriers
Dominant Inheritance
Autosomal Dominant Conditions Achondroplasia – dwarfism Familial Breast Cancer – BRCA1 and 2 Huntington Disease
Crouzon’s Syndrome
Premature fusion of the skull bones
Wide, shallow eyes
Hearing loss
X-Linked Inheritance
X-Linked Traits
Color blindness Hemophilia Fragile X
x-linked dominant: “Incontinentia pigmenti” -various severity from skin abnormality to CNS problems
Fragile X Syndrome Most common cause of
inherited mental impairment
Caused by expanding area of DNA on chromosome X (CGG Repeat)
Prevalence: – 1 in 4000 males – 1 in 6000 females – All races and ethnic groups
What Happens During a Genetic Counseling Session? Family history is taken Discuss medical/genetic
problems in general Provide risk assessment Discuss testing options,
in terms of risks, benefits and limitations
Consent patient for testing
Pedigree Construction Geneticists’ fundamental tool Allows for easy construction of a multi-
generational family history Simple method for detailed
documentation of inheritance of a particular trait in a family
Can often assess the inheritance of a trait based on pattern of affected individuals
Pedigree Fundamentals
Autosomal Recessive(it can be hidden and reappear)
What inheritance pattern?
Autosomal Dominant
What inheritance pattern?
X-Linked Dominant(if father carries, every girl has it)
What inheritance pattern?
Y-linked(all sons of affected fathers are affected, ex; TDF-testes determining factor)
Any ideas on this one?
Mitochondrial Inheritance(all children get mitochondria of mother)
Prenatal Genetics Women who are at
increased risk to have a child with a genetic disorder/ birth defect– Advanced maternal age– Family history of medical
problem/genetic disease– Exposure to drugs,
alcohol, medication– Prenatal sonogram
abnormalities
Maternal Age Effect
As the age of the mother increases, there is an increased risk for a chromosome abnormality in their child.
Different Prenatal Testing
MSAFP – (test mother’s blood)
Amniocentesis CVS Nuchal Fold-
– sonogram measures amount of fluid in fetus’ dorsal neck
Maternal Serum Screen
AFP HCG uE3 Inhibin A
Down
Syndrome
Trisomy
18
N/A
Neural Tube Defect N/A N/A N/A
Neural Tube Defects
Diagnostic Testing CVS – Chorionic
Villi Sampling Amniocentesis
Case 1
Mother is 28 years old Maternal Serum Screen indicates 1/30
for Down Syndrome
TeratogensThalidomideMedications for maternal illness
Osteogenesis Imperfecta
Marfan Syndrome
Ehlers-Danlos Syndrome
Neurofibromatosis
Prader-Willi Syndrome
Treacher Collins Syndrome
Case 2: Huntington Disease
Woman is 31 years old Has a sister and father with HD Wants to be pregnant without knowing
her HD status Goes through 2 rounds of
Preimplantation Genetic Diagnosis (PGD) unsuccessful
At 34 she becomes pregnant naturally
Case 3: Cancer Genetics
Breast cancer in a family with Ashkenazi Jewish heritage
Unaffected father worried about two daughters: 28 and 23 yrs
Information Websites National Society for Genetic Counselors
http://www.nsgc.org The American Board of Genetic
Counseling (ABGC)
http://www.abgc.net Canadian Association of Genetic
Counsellors
http://www.cagc-accg.ca
Caroline LieberDirector of The Joan H. Marks Graduate Program
in Human Genetics
Sarah Lawrence College
1 Mead Way
Bronxville, NY 10708
Tel: 914.395.2371
http://www.slc.edu/grad_humangenetics.php
For more information contact:For more information contact: