Topic 12-1 Flashcards
a pictorial representation of a family history, essentially a family tree outlining inheritance of one or more characteristics
pedigree
horizontal lines in pedigrees represent:
matings b/w mother and father
vertical lines in pedigrees represent:
they connect a mating to a child or children
males are represented by _______ in pedigrees
squares
females are represented by _______ in pedigrees
circles
people with unkown or unspecified sex are represented by _______ in pedigrees
diamonds
the presence of a certain trait are represented by:
coloured in shapes
if a person is suspected to have the mutant gene but does not display the trait they are called:
obligate carriers
obligate carriers are represented by _______ in pedigrees
a dot and not a filled in shape
pedigrees are initiated when a particular family member with a trait is studied. this family member is called the:
proband
probands are designated with:
a āPā and an arrow pointing at the person/shape
limited numbers of offspring make ________ impossible to discern, thus we must be _______
mendehlian ratios, genetic detectives
autosomal recessive traits:
- normally appear with equal frequency in both sexes
- occurs only when a person inherits an allele from each parent
- if trait is rare, traits can skip generations
- if progeny keep mating outside the family, then the trait can be passed down for many generations without appearing
when considering autosomal recessive traits, traits are more likely to appear:
among progeny of related parents
mating between closely related people
consanguinity
how is consanguinity represented on a pedigree?
parallel horizontal lines
what is an example of an autosomal dominant trait?
familial hypercholesterolemia
what is familial hypercholesterolemia?
a disease characterized by a defect in cholesterol transport which leads to greatly elevated cholesterol
familial hypercholesterolemia in heterozygous individuals:
- blood LDL levels are 2x normal levels
- susceptible to heart attacks by age 35
familial hypercholesterolemia in homozygous individuals:
- blood LDL levels are 6x higher than normal
- heat attacks b/w 2-20 years of age
true or false: autosomal dominant traits skip generations
false
X-linked recessive traits have:
- a distinctive pattern of inheritance
- occur more frequently in males
males with X-linked recessive traits are born to _________ mothers
obligate carrier
are X-linked traits passed from father to son?
no
what is one example of an X-linked recessive trait?
hemophilia A
how have some heterozygous females been able to experience milder forms of hemophilia?
X chr inactivation
X-linked dominant traits:
- appear in both males and females
- offspring with trait must have a parent displaying a trait
- affected men pass to all of their daughters but none of their sons
- affected heterozygous women pass to half of their daughters and half of their sons
what is an example of an X-linked dominant trait?
hypophosphatemia (vitamin D resistant rickets - soft bones)
Y-linked traits:
- only males are affected
- does not skip generations
- neither dominant or recessive
