Pedigree Analysis (Lec 8) Flashcards
What is Hutchinson-Gilford Progeria Syndrome?
Inherited as an autosomal dominant trait; children show accelerated aging, hair loss, heart disease - usually die from coronary artery disease
In regards to a pedigree, what is a pro band?
the person from whom the pedigree is initiated
Deafness, fair skin, visual problems, and a white forelock are indicative of what ?
Wardenburg Syndrome; autosomal dominant
What are some characteristics of an autosomal recessive trait?
appears in both sexes with equal frequency; trait tends to skip generations; affected offspring are usually born to unaffected parents; when both parents are heterozygous, approximately 1/4 of the offspring will be affected; appears more frequently among children of consanguineous marriages
What are some characteristics of an autosomal dominant trait?
appear in both sexes with equal frequency; both sexes transmit the trait to their offspring; does not skip generations; affected offspring must have an affected parent, unless they possess a new mutation; unaffected parents do not transmit the trait
This disease is an inherited disease in which blood cholesterol is greatly elevated due to a defect in cholesterol transport
Familial Hypercholesterolemia
Cholesterol is transported throughout the body in small particles called what?
lipoproteins
LDL’s (low-density lipoproteins) are transported to cells and attach to receptors where?
on cell membrane
What is defective in familial hypercholesterolemia?
the cell membrane receptor
Will only having one defective LDL receptor allele be enough to cause elevated blood cholesterol levels?
yes; LDL levels are twice as normal and individuals usually have heart attacks by the age of 35
What are the effects of being homozygous for the defective LDL receptor allele?
LDL levels may be 6x normal; may suffer a heart attack by the age of 2 and inevitably by the age of 20
Familial hypercholesterolemia is said to be ____ ____. Homozygotes are rarely seen, and the heterozygous form appears to be inherited as a simple dominant trait
incompletely dominant
More males than females affected; affected sons are usually born to unaffected mothers - trait skips generations; approximately 1/2 of a carrier mother’s sons are affected; it is never passed from father to son; all daughters of affected fathers are carriers
The characteristics above describe what type of trait?
X-linked recessive
What are some characteristics of an X-linked dominant trait?
both males and females are affected; often more females than males are affected; does not skip generations; affected sons must have an affected mother - affected daughters must have either an affected mother or father; affected fathers will pass on the trait to all their daughters; affected mothers (if heterozygous) will pass the trait on to 1/2 of their sons and 1/2 of their daughters
What are some characteristics of a Y-linked trait?
only males are affected; it is passed from fathers to sons; it does not skip generations
What is it called when both members of a twin pair express a trait?
concordant twins
What is it called when only one member of a twin pair expresses a trait?
discordant twins
define concordance
percentage of twin pairs in which both members of the pair express the trait
True or false?
genetically influenced traits should exhibit higher concordance in monozygotic twins
true
Obesity is an example of what type of trait?
multifactorial trait
The obesity gene in mice produces a protein called what?
leptin
What does leptin do?
decreases appetite by affecting the hypothalamus
What are adoption studies used for?
to analyze inheritance in humans
similarities between adopted children and their biological parents indicate the importance of genetic factors in expression
similarities between adopted children and their adoptive parents indicate the influence of environmental factors
True or false?
Ultrasonography can be used to detect genetic disorders?
true
amniotic fluid and a small portion of the chorion can be used for testing
