Exam 1: Lecture 8 & 9 Flashcards
adermatoglyphia
absence of ridges on the skin of the pads of the fingers and toes
obligate carrier
carries the gene but does not have the trait (dot inside unaffected m/f pedigree symbol)
proband
first affected family member coming to attention of geneticist (āPā next to affected m/f pedigree symbol)
special features of human biology that hinder genetics research
- controlled mating is not possible
- long generation time
- small family size
ethics: the nuremberg code
voluntary consent is essential
ethics: the declaration of helsinki
world medical association set guidelines for medical doctors in biomed research involving human subjects
ethics: belmont report
ethicist and researchers rules refined (all nations)
pedigree
pictorial summary of family anomalies
pros of a pedigree
- diagnostic tool to guide decisions
- pattern of transmission
- early identification to reduce risk
autosomal recessive
appear with equal frequency in both sexes and seem to skip generation
why are autosomal recessive traits more likely to appear among progeny of related parents
high probability the related parents will carry the same set of damaging mutations and therefore higher probability that their children will inherit the recessive/damaging alleles
autosomal dominant
goes to both sexes (children) from both sexes (parents) ie eliminate from being on x chromosome
could there be a case when a person affected by an autosomal dominant disorder does not have an affected parent?
yes; where do new mutations come from? they arise all the time, meiosis/mitosis. arrive de novo (new/unique)
x-linked recessive: woman
woman is carrier = masked (normal phenotype)
offspring: 50:50 chance daughter will be carrier; pass more to sons
x-linked recessive: man
males are affected and do not pass the trait to his sons
y-linked traitrs
appear only in males and father passes to all his sons (rare, not many genes involved)
twin studies are good for:
genetic location and genetic behavior
concordant trait
a trait shared by both members of a twin pair
concordance
the % of twin pairs that are the same (concordant) for a trait
does the trait examined in twins show phenotypically the same?
no, trait may not be exactly the same phenotypically due to differences in penetrance or other factors (environment)
do monozygotic twins have the same genetic sequence
yes identical
if identical twins are adopted, where do developmental differences come from?
more likely due to environmental factors
dizygotic twin genetic similarity?
the same genetic similarity as brothers and sisters born from different pregnancies (2 eggs and 2 sperm)
chorionic villus sampling (CVS) and amniocentesis
obtaining fetal cells for genetic testing
