Genetics Flashcards
when do most malformations appear
by the 8th week- but the brain can be affected several months after birth- breastfeeding
what is an example of a physical teratogen
X-ray other radiation sources
what is an example of a chemical teratogen
Thalidomide
Alcohol: IUGR, Dev of brain
what is an example of a microbial teratogen
torch
what is TORCH
T: Toxoplasma O: Other less common infections: EBV, Listeria R: Rubella C: cytomegalovirus H: Herpesvirus Transplacental, Period of organogenesis
What is Congenital Rubella Syndrome
Microcephaly Microphthalmia Heart desease Petechiae and purpura- red spots on skin Eye - cataracts, glaucoma, strabismus, nystagmus,
what are some chromosomal abnormalities
Structural Chromosomal abnormalities: Deletion: WAGR Translocation: Numerical chromosomal abnormalities: Trisomy 21, Trisomy 18, Trisomy 13
what is deletion
removal of part of the chromosome
what is Translocation
part of one chromosome is on another
what is trisomy21
3 chromosomes at nuber 21
down syndrome
Pathogenesis:
Meiotic nondysjunction of maternal chromosome 21 pair –95% (47 chromosomes)
Most common (1 in 800 neonates) 1 in 50 in women older than 35 years of age
what is Turners syndrome
X0 Turners: Short stature Webbing Broad chest Abnormal extremities Undeveloped ovaries: streak gonads—
lack secondary sex characteristics—
Usually lethal in utero—
High incidence in spontaneous abortions
kLINEFELTER syndrome
XXY 1:700, Phenotypically male Tall, thin, long legs gynecomastia, Underdeveloped secondary sex ch. Infertile Atrophic Testes
what is Marfan’s syndrome (AD)
1 in 10,000, AD,
Mutation in Fibrillin -1gene (ECM gp,
Polymerizes to form microfibrils in both elastic and non elastic tissues
Multisystem Disorder: Sk, ocular, CV, skin, lung Disproportionate tall stature Skeletal abnormalities Ectopia lentis Mitral valve prolapse Aortic aneurysm Spontaneous pneumothorax
what is an autosomal recessive disorder
Trait that is expressed only in homozygotes or compound heterozygotes
Parents of affected homozygotes are asymptomatic
Children of affected homozygote (normal partner) are not symptomatic
no these numbers!!!!
Progeny of two HZ : 25% N; 25%Affected
50%: Carriers
Skip generations
what is cystic fibrosis
Most common AR, 1 in 2500, 1 in 25 of northern Caucasian descent : carrier
Gene: codes for chloride transport channel in cell membrane
what are the symptoms of cystic fibrosis
dont need to know exactlyreocurrent pulmonary infections, lung abscess brinchitis, honey comb lung, abnormal sweats, pancreitis, malabsorption
wha tis X-Linked recessive disorder
Recessive genes located on X chromosomes
Incidence higher in males
HZ females are unaffected. (transmit to 50% of sons and daughters)
Gene responsible for the condition is transmitted from an affected man through all his daughters. Daughter’s son have 50% chance of inheriting it. Sisters of affected male are asymptomatic.
Mutant allele is never transmitted directly from father to son but to all the daughters, who are carriers.
what is hemophilia
X-linked bleeding disorder: bleed into muscle, joints, soft tissue
Males affected, 1 :5000
Due to mutation in factor VIII gene
whyat are the signs of hemophilia
Easy bruising
Spontaneous Joint and Muscle hemorrhage
Prolonged bleeding from wound
which of the following are incorrect:
A. Most critical period of organogenesis is first trimester of pregnancy.
B. Brain development can be affected upto last trimester.
C: Clinical manifestations depend upon viral agent and gestational age at exposure.
D. Reactivation of CMV in first trimester has no effect on fetal growth.
E. Common known teratogen is alcohol
a: correct-up to 12weeks
b:
c:
d:
e:
d?
adter what stage of the embryo do defects appear
the blastocyte stage- before this cells are not commited
what is the merula stage
not commited- could remove cells and still be ok
when is the most critical time of oligogenesis
8-12 weeks
75% of the causes of human defects are caused from
unknown
