Flashcards in Genetic diseases I Deck (102):
Derived from ones parents and transmitted through the gametes
Origin of defect
How many generations have had defect; can be expressed or not expressed
Genetic disease that occurs sporadically
Any abnormality present at birth
mutation of a single gene of large effect
disorders with multiple genes as well environmental influences
Complex Multigenic Disorder
Disorders with multifactorial inheritance
Complex Multigenic Disorders
disorder where phenotypic expression is related to the combined effects of environmental influences and multiple genes of small effects (polygenic inheritance )
Complex multigenic disorders
diseases arising from chromosomal aberrations that are identifiable on karyotype
Cytogenic Disorders (Chromosomal Disorders)
ingle-gene Disorders with Atypical Patterns of Inheritance
1. single gene defects that do not follow Mendelian patterns of inheritance
What are examples of single gene disorders w/ atypical patterns of inheritance?
a. Triplet repeat mutations and mutations in mitochondrial genes
b. Disorder with genomic imprinting – transmission is influenced by epigenetic phenomena
A karyotype is constructed from photographic images of patient cells in
What stain is widely used as the G banding technique?
Karyotypes can be performed on children and adults by culturing what types of cells?
Lymphocytes from the peripheral blood
Karyotypes can be performed on fetuses by culture of what cells?
Fetal fibroblasts from amniotic fluid or placental sampling
up arm-"p" for petit
down arm "q"
at ends of p
“p” and “q” arms are of equal length.
“p” arm is shorter than “q” arm.
“p” arms are very short and have satellites
How is a karyotype arranged?
Metacentric-> subcentric-> acrosentric->sex-chromosomes (acrocentric)
When is the earliest amniocentesis can be performed?
Which test can be performed at 10 weeks?
Chorionic villi sample
any exact multiple of the haploid number
multiples of the haploid number beyond 2n, such as 3n, 4n, 5n, etc.
a. any number of chromosomes that is not an exact multiple of n
Examples – (n + 1), (n - 1), (2n + 1), (2n - 1)
defined as two or more karyotypic populations of cells in the same individual. Occurs more commonly involving the sex chromosomes.
What are the 2 types of translocations?
1. Balanced reciprocal translocation
2.Robertsonian translocation or centric fusion
1) fragments are exchanged between two chromosomes and no genetic material is lost.
Balanced reciprocal translocation
reciprocal translocation that always occurs between two acrocentric chromosomes
Robertsonian translocation or centric fusion
in which translocation do we ALWAYS get loss of genetic material?
Robertsonian translocation (centric fusion)
a. Centromere divides transversely so that the two short arms are paired and the two long arms are paired.
Loss of a portion of a chromosome
What is worse having extra chromosomes or missing chromosomes?
1) One chromosome breaks, then the broken segment makes a complete turnaround and reattaches to the original chromosome.
what are the 2 patterns of inversion?
Paracentric and pericentric
have both breaks on the same side
have breaks on either side of the centromere
which chromosome aberrations have structural abnormalities?
which chromosome aberrations have numerical abnormalities?
2 or more distinct karyotypic cell populations in the same individual
mosaicism is an abnormality that occurs due to what?
deletion that occurs at both ends of a single chromosome, then damaged ends fuse
what are abnormalities that create re-arranged material?
Translocations and inversions
Abnormalities involving ____are generally more severe than defects involving _____________
a missing ______ is not compatible with life
how do most cytogenic disorders arise?
arise De Novo in the gametes
disorder is neither in the parental line nor is it familial
chromosomal abnormality arises during gametogenesis
What are the cytogenic disorders involving autosomes?
Trisomy 21- Down syndrome
Trisomy 18- Edwards syndrome
Trisomy 13- Patau syndrome
incidence 1: 1700 live births
47XX +21 or 47XY+21
% of down syndrome caused by translocation?
% of down syndrome mosaics
46XX/47 XX +21
down syndrome mosaics
what tests do you use to diagnose Down syndrome?
First trimester screening test and Karyotyping
identifies polymorphicgenetic markers of fetal free DNA in maternal blood
First trimester screening test
when is the first trimester screening test done?
11-13 weeks gestation
which disorder has horizontal palmar crease/ simian crease?
which disorder has hypotonia?
which disorder has congenital heart defects?
e.g.atrial septal defect
which disorder has high risk for developing Alzheimer's?
which disorder has late face and epicentral folds?
what are the most common causes of death for down syndrome?
what is the median life expectancy for DS?
60 years old
which disorder has predisposition for autoimmune thyroid disease-> hypothyroidism?
incidence 1:8,000 live births
47,XY,+18 or 47,XX,+18
which disorder displays prominent occiput?
which disorder displays micrognathia?
which disorder displays hypertonicity?
which disorder displays horse shoe kidney?
which disorder displays crossed fingers
which natural position in edwards syndrome persists in death?
which disorders display rocker bottom feet?
edwards and patau
Incidence 1:15,000live births
47,XX,+13 or 47,XY,+13
which disorder displays microcephaly?
which disorder displays micropthalmia?
which disorder presents with cleft lip and cleft palate?
which disorder presents with polydactyly
what are the cytogenic disorders involving sex chromosomes?
incidence 1:1,000 to 1: 1500 live male births
up to 15% mosaics
which syndromes have hypogonadism?
Kleinfelter syndrome and turners syndrome
elevated urine are clinical features of what disorder?
breast development in men
gynecomastia inKleinfelter syndrome
Elongated body appearance -long legs particularly in femur
mild decreased intelligence relative to other family members
increased risk for breast cancer, extragonadal germ cell tumors and autoimmune disease
incidence 1: 2,500-1:2,000 live female births
Monosomy-only one sex chromosome
% mosaics in turners syndrome?
possible problems with cystic hydromas?
which syndrome manifest short stature?
Webbed neck and low posterior hair line
broad (shield) chest