Genetic Func Flashcards
(19 cards)
Polyploidy
- cells with complete set of extra chromosomes (often seen in plants)
- cells with normal number of chromosomes
Euploid
- cells contain a missing chromosome or additional individual chromosomes
- Likely due to nondisjunction
- Cause of Down Syndrome, Edwards, and Patau
Aneuploidy
- Improper separation of homologs during meiosis I or II
- Major cause of mitotic errors
- Increases with maternal age. As mother’s get older, there is more opportunity for mother’s somatic cells to be mutated.
Nondisjunction
- UPD is a phenomenon when individual receives two copies of chromosome or part of a copy from one parent and no copy from the other
- Often asymptomatic as pt. still has one copy of each gene
- Prader-Willi syndrome occurs from this, leads to uncontrolled eating, obesity
Uniparental Disomy
- Normal process
- One copy of gene is silenced due to parental origin
- Epigenetic process that involves methylation/histone modification of 5’ end of gene on egg/sperm during their formation (Note: genetic sequence unchanged)
- Certain genes only expressed from father or mother
- Imprinted alleles are silenced such that the gene is expressed only from non-imprinted allele
- Erased in germ cells at each generation
Genetic Imprinting
Robertsonian Translocation
13, 14, 15, 21, 22)
• Exchange of material between two chromosomes.
• 13 and 21 cause Patau and Down’s respectively.
What syndrome is caused by a deletion is on the paternal chromosome (15)
Prader Willi
i. Short, hypotonia, small hands and feet, fat, mild-moderate intellect disability, uncontrolled eating
- Think of a small willi-cauli stein at 15 yrs…short, w/ small hands (opposite of now)`
47, XXY syndrome
Kleinfelters
Small, undescended testes, breast development gynecomastia, infertility, cognitive, social, behavioral, and learning difficulties, tall
-more X’s increase symptoms
-Klein is a real ladies man
Trisomy 13
Patau Syndrome 47, xx+13
Most die before birth, 13% survive to 10 y.o. Clenched fist, polydactyl, Heart, kidney, CNS dysfunction. Microencephaly, malformed ears, close/absent eyes, cleft palate
-Gollum Platau’d at age of 13
Trisomy 18
Edwards Syndrome 47, XX+18 Often IUGR (in utero growth restriction), less than 10% of births survive >1 year, microencephaly, malformed, low-set ears, small mouth and jaw, cleft palate, rocker bottom feet, overlapped fingers -Edward Scissorhands had 18 oddly bent fingers and legs with a strange head
Trisomy 21
Downs syndrome 47, XX+21
Cardiac defects, duodenal atresia (blocking intestines), cognitive impairment (varies), increased nuchal translucency, short limbs, flattened nose/face, upward slanting eyes
-associated with maternal age
45, XO missing chromosome (no Y)
Turner syndrome
-Short, ovarian failure, do not undergo puberty, webbed neck, low hairline, NO cognitive deficits
Might cause generational skips on a pedigree, like in retinoblastoma
Incomplete penetrance
A single disorder caused by genes in different chromosomal loci
Locus Heterogeneity
Osteogenesis Imperfecta Syndrome
Blue sclera, Brittle Bone disease, collagen
Syndrome
Osteogenesis Imperfecta
Mosaicism
-two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg
Cousins are more likely to produce rare autosomal recessive disorders
Consanguinity
Heteroplasmy
- Because each cell contains a population of mtDNA molecules, a single cell can harbor some molecules that have an mtDNA mutation and other molecules that do not. This heterogeneity in DNA composition, termed heteroplasmy, is an important cause of variable expression in mitochondrial diseases.
Mito must undergo many divisions before sufficient amount to cause symptoms, so deveops later in adulthood
