Pedigree Concepts Flashcards
“Genetic counseling” was coined by
Sheldon Reed
In 1971, the first batch of trained genetic counselors were trained; nowadays, should have a ____
masters degree
4 reasons for patient to see genetic counselor
family history of Cancer, multifactorial disease, abnormal chromosomes, single gene disease
2 genetic testing techniques
karyotype and amniocentesis
Genetic analysis method to determine disease
family history
Genetic testing technique
Genetic counselor deduce dominance and distinguish autosomal from X-linked inheritance
Pedigree analysis
family tree,” drawn with standard genetic symbols, showing inheritance patterns for specific phenotypic characters
pedigree chart
Squares represent ___ and Circles represent ____
square: males ; circles:females
Shaded squares or circles signify the presence of ___
trait of interest
Rows are ____, labeled with ____.
generations, roman numerals
t/f: Within each generation, or row, family members may be labeled numerically from right to left and referred to by their generation and position.
false, left to right
horizontal line connecting two parents is called a
marriage line
A vertical line of descent extending downward from a marriage line connects to a horizontal ____
sibling line
Individuals connected to the line of descent via the sibling line are ___.
off spring
One mutated allele causes the disease Each affected person usually has one affected parent Appears in every generation of an affected family (Vertical)
Autosomal dominant
Inheritance Pattern: Marfan syndrome; Achondroplasia; Huntington disease; Myotonic dystrophy
Autosomal dominant
inheritance pattern: Two mutated alleles needed to cause the disease Parents are usually unaffected heterozygotes Not typically seen in every generation (Horizontal).
Autosomal Recessive
Inheritance pattern: Females are more frequently affected than males no male-to-male transmission
X-linked dominant
Inheritance pattern: Males are more frequently affected than females Both parents of an affected daughter must be carriers Fathers cannot pass X-linked traits to their sons
X-linked Recessive
Inheritance pattern: Only females can pass on mitochondrial conditions to their children (maternal inheritance) Both males and females can be affected Can appear in every generation of a family
Mitochondrial
Inheritance Pattern: Beta thalassemia; Cystic fibrosis; Homocystinuria
Autosomal Recessive
Inheritance Pattern: Rett syndrome; Hypophosphatemia
X-linked dominant
Inheritance Pattern: Hemophilia; Duchenne Muscular Dystrophy
X-linked Recessive
Inheritance Pattern: LHON: Leber’s hereditary optic neuropathy
Mitochondrial
All except one pertains to Autosomal Dominant
a. approximately half of everybody
b. males and females affected
c. consanguinuity
d. all generations
c. cosanguinity
All except one pertains to Autosomal Recessive
a. every child of affected mother is affected
b. Rare
c. Skips generations
d. Males and females affected
e. Consanguinity
a. every child of affected mother is affected
All except one pertains to X linked dominant (sex-linked dominant)
a. some females can have it
b. all generation (no skipped generations)
c. males generally get it from unaffected mothers and give it to their daughters
c. males generally get it from unaffected mothers and give it to their daughters
all except but one pertains to X linked recessive (sex-linked recessive)
a. rare
b. males predominantly have it
c. generally skips generations
d. males generally get it from unaffected mothers
e. approximately half of everybody
e. approximately half of everybody
all except but one does not pertain to Y linked
a. all males all the time, all generations (mus tbe direct descedent of the family)
b. some females can have it
a. all males all the time, all generations
t/f: every child of affected mother is affected in mitochondrial or maternal
TRUE
Traits caused by genes on autosomes and requiring two allele copies to influence a phenotype are _______
autosomal recessive trait
Several disorders are _____, including cystic fibrosis, Tay-Sachs disease, and maple syrup urine disease.
autosomal recesivve
Most people with these diseases have heterozygous parents who do not have the condition but carry a causal allele.
autosomal recessive trait
These carriers can unknowingly impart the disease to their children, which partially explains why _______ are more common than their dominant counterparts.
autosomal recessive trait
Neither parent has the trait, but one child inherits it. Thus, it must be ____
recessive
A human metabolic disease caused by a mutation in a gene encoding a phenylalanine- processing enzyme, which leads to mental retardation if not treated; inherited as an autosomal recessive phenotype
Phenylketonuria (PKU)
These are requiring only one copy of the determining allele to influence phenotype
autosomal dominant trait
Freckles and polydactylism (extra fingers or toes) are examples
autosomal dominant trait
_____ diseases, such as Huntington’s disease,
afflict ~50% of offspring with one affected parent.
autosomal dominant trait
Many of these diseases do not cause symptoms until later in life and or after reproductive age.
autosomal dominant trait
Children can inherit these diseases from unknowingly affected parents, highlighting the importance of analyzing family history.
autosomal dominant trait
an autosomal dominant genetic disorder that affects the central nervous system of human beings.
Huntington’s disease
This disease typically shows up when a person reaches their mid 30’s or 40’s, with no earlier signs or symptoms.
Huntington’s disease
The nerve cells of an affected individual quickly degenerate in certain parts of the brain, which leads to symptoms that include dementia, loss of memory, and severely decreased mental capacity, muscle rigidity, and loss of bodily function and muscle coordination.
Huntington’s disease
usually shortens an affected persons lifespan, with the average person dying 15-20 years after onset of the disease, making the life expectancy around 50-60 years of age.
Huntington’s disease
- Trait is rare in pedigree.
• Trait skips generations.
• Affected fathers DO NOT pass to their sons.
• Males are more often affected than females
X linked recessive
t/f: in X-linked recessive, carrier mother’s son have 0% of having disease
false, 50%
t/f: in X-linked recessive, male to male transmission is not allowed
TRUE
t/f: in X-linked recessive, only one defective copu is necessary for disease in males
TRUE
What inheritance pattern
Red-green color blindness
Hemophilia
• X-linked ichthyosis
X linked recessive
t/f: in X-linked dominant, male to male transmission is not seen
TRUE
t/f: x linked are unusual and lethal in males
TRUE
incontinentia pigmenti (skin lesions)
x linked dominant
X-linked rickets (bones soften/deform)
x linked dominant
t/f: Y-linked genes can only be transmitted from father to son
TRUE
Y-linked inheritance is also called ____
holandric inheritance
t/f: in mitochondrial, only transmitted from affected male and gives to all offspring
false, female
presentation timing of mitochondrial
usually after puberty
in mitochondrial, there is variable expression due to ___
heteroplasmy
genders affected in mitochondrial
equal male and female
t/f: mitochondrial skips generations
FALSE
genders affected in X linked dominant
equal male and female
Generations affected: X linked dominant
does not skip generations
females of affected fathers are always affected
male or females of affected mothers can be affected
presentation timing of X linked dominant
usually after puberty
Genders affected: X linked recessive
males must receive defective gene from carrier mother
affected males give copy to all of their daughters
