Week 3 concepts and definitions Flashcards
What is mosaicism?
The presence of 2 or more genotypes in an individual derived from one zygote
What is the difference between mosaicism and chimerism?
Chimerism is two genotypes present in one individual (usually the result of the fusion of two zygotes), while mosaicism is one genome present in the individual (usually the result of a mitotic error during development)
What is the difference between somatic and germline mosaicism?
Germline mosaicism is confined to the germ cells, while somatic mosaicism can occur in any cell except for germ cells
What is genomic imprinting?
A parent-of-origin difference in gene expression due to epigenetic modification
What is uniparental disomy (UPD)?
Both members of a chromosome pair (or part of a chromosome) are inherited from one parent, usually due to trisomy with a loss of one of the extra chromosome around fertilization
What are the genetic mechanisms of imprinting disorders?
Deletion of gene on the appropriate parent, uniparental disomy of the opposite parent, imprinting defect that silences the gene on the appropriate parent
What is anticipation in the context of trinucleotide repeat disorders?
The tendency of an increase in the number of trinucleotide repeats in subsequent generations
What factors affect the pathogenicity of a repeat expansion?
Sequence/size of repeat, location of repeat within gene, whether repeat encodes RNA or protein, function of affected gene
What is heteroplasmy?
The presence of both normal and mutant mitochondria
How are mitochondrial diseases inherited?
Maternally inherited; both males and females can be affected, but individuals can only inherit the disease from their mother
What is a teratogen?
A drug or other agent that causes abnormal development in the embryo or fetus; an exposure in pregnancy that has a harmful fetal effect
What is teratology?
The study of environmentally induced congenital anomalies
What factors affect the teratogenicity of an agent?
Timing, dose (amount/frequency/duration), fetal and maternal metabolism, genetic susceptibility
When is the growing individual most sensitive to teratogens?
During organogenesis (weeks 2-9, first trimester)
In general, what abnormalities arise during each trimester of pregnancy?
First trimester - congenital malformation; second and third trimester - IQ
