genetics 3 Flashcards
1
Q
define Anticipation
A
- genes rendered abnormal by amplification of CG-rich units
- these diseases get worse from generation to generation as amplification continues
- the disease appears sooner in the son than in the father (anticipation)
2
Q
describe Fragile X syndrome
A
- leading cause of INHERITED mental imapirment
- X-linked DOMINANT (with reduced penetrance)
- Assocaited with CGG repeats in FMR1 gene on X chromosome (>200 Cgg repeats)
- Diagnosed via southern blot or PCR
3
Q
define intermediate range
A
- refers to a range of repeats that is normally stable
4
Q
define premutation range
A
- always changes in size (usually an expansion)
- expansion from pre- to full mutation only occurs through FEMALE Meiosis
5
Q
describe the clinical characteristics of Fragile X syndrome
A
- CGG repeats
- severity of disease correlates with # of repeats
- Big ears, Big upper jaw, Big testicles
- mental retardation, behavior problems, long, characteristic face (prominant Jaw and protruding ears)
- High arched palate
- large gonads
- AFFECTED FEMALES TEND TO HAVE MILDER FEATURES
6
Q
describe Huntington’s disease (HD)
A
- HD gene on chromsome 4 encodes for HUNTINGTIN (protein widely expressed by neurons and glia of CNS)
- HD is an AUTOSOMAL DOMINANT condition caused by expression of CAG trinucleotide repeats in the HD gene
- people with HD have >36 CAG repeats
7
Q
describe the clinical characteristics of HD
A
- progressive disorder of motor, cognitive, and psychiatric changes
- mean age = 36-44
8
Q
describe EARLY stage of HD
A
- sublt changes in coordination, minor chorea (involuntary jerky movements), difficulty mental planning and often a depressed or irritable mood
9
Q
describe Middle stage
A
- Chorea becomes more prominent with increasing difficulty with voluntary activity and worsenign dysarthria and dysphagia
10
Q
describe late stage of HD
A
- behavior problems are gradually lessened; motor disability becomes severe and the individual is often totally dependent, mute and incontinent
11
Q
describe late stage of HD
A
- behavior problems are gradually lessened; motor disability becomes severe and the individual is often totally dependent, mute and incontinent
12
Q
Describe Edwards syndrome
A
- chromosomal disorder caused by the presence of all or part of an extra CHROMOSOME 18 due to NONDISJUNCTION during meiosis
- low rate of survival resulting from heart abnormalities, kidney malformations and other internal organ disorders
13
Q
Patau syndrome
A
- extra genetic material from CHROMOSOME 13
- -> full extra copy or extra partial copy (robertsonian translocation) of chromosome
- 80% of die within first year of life (physical development and muscle devleopment is slower)
14
Q
describe turner syndrome
A
- 45, X
- Monosomy X results when an individual inherits ONE X chromosome and no second sex chromosome
- Individuals are FEMALE
15
Q
describe the clincial features of turner syndrome
A
- Prenatal = common cause of miscarriage; some patients are detected by finding icnreased fluid, swelling, CYSTIC HYGROMA about the neck, or hydrops
- Birth = residua sings of prenatal lymph blockage including webbed neck, puffy hands and feet, low-set, rotated ears
16
Q
Cystic hygroma
A
- characteristic feature of turner syndrome
- not a true neoplasm, but failrue of lymphatics to forma nd drain properly
- eventually forms the webbed neck feature of women with turner syndrome
17
Q
Describe the characteristics of people with turners syndrome
A
- absence of second dose of genetic ifnormation contained on the short arm of the X-chromosome
- short stature
- absence of ovaries and failure to proceed through puberty (sexual infantilism)
- characteristic facial features (traingle-shaped face, posteriorly rotated ears)
- broad webbed neck
- broad sheild like chest
- short 4th metacarpal
- FAILURE TO MENSTRUATE (Amenorrhea)
18
Q
describe Klinefelter sydrome (KS)
A
- 47, XXY
- presence of an EXTRA X chromosome (1-1000 boys)
19
Q
describe the characteristics of Klinefelter syndrome
A
- be taller than average
- longer arms and legs than usual
- develop breast tissue during teen years (gynecomastia)
- HYPERESTROGENISM (icnreased risk of berast cancer!!!)
- have smaller genitals that average (hypogonadism)
- atrophy of seminiferous tubules leads to sterility
- learning diabilities and social immaturity
20
Q
describe the characteristics of Klinefelter syndrome
A
- be taller than average
- longer arms and legs than usual
- develop breast tissue during teen years (gynecomastia)
- HYPERESTROGENISM (icnreased risk of berast cancer!!!)
- have smaller genitals that average (hypogonadism)
- atrophy of seminiferous tubules leads to sterility
- learning disabilities and social immaturity
21
Q
define imprinting
A
- given gene has methyl groups attached to its cytosine nucleotides (methylated)
- methylated genes are NOT actively transcribed and translated into protein, so these genes are essentially TURNED OFF (inactivated)
- deviation of the normal methylated genes can cause genetic disease
22
Q
describe Prader-Willi syndrome
A
- patients lack the normal gene from their FATHERS
- -> inherited dads mutant (typically deleted) gene (del of 15q11)
- Truncal obesity, hypogonadism, small hands
- overeat, incorrigibly stealing and hiding food and become very obese
- prone to a outbursts of extreme violence
23
Q
describe angelman syndrome
A
- patients lack the normal gene from their MOTHERS
- -> inherited moms gene deletion (del of 15q11)
- wide stance, arm position, spasticity
- severely retarded, with microcephaly and huge jaws
- they have jerky, puppet like movements and laugh a lot
- NO SPEECH
- severe ataxia
- paroxysmal laughter
