chromosomal abnormalities
Terms
undefined, object
copy deck
- Explain telomeres and their role in replication
-
-forms a triple helix loop that's stabilized by proteins
-telemorase provides template for RNA
-active in gamete prod.
-prevents degradation of DNA after RNA primer is removed - Define Lyonization
-
every extra X chromo is inactivated
others randomly turned on
female are mosaics for expressions of the trait
i.e. Anhidrotic Dysplasia - List the steps involved with the study of chromos in a lab
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-Draw bld
-Grow in media
-Add chems to block division past metaphase
-Harvest and fixate
-let a drop fall on a slide
-cell lysis, chromos spill out
-add chems to see a banding pattern - Karyotyping
-
orders chromos in:
-size
-position of centromere - Describe how non-banded chromos are grouped
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A 1-3: big,metacentric
B 4-5:submetacentric
C 6-12(X):submeta
D 13-15:acrocentric
E 16-18:submeta
F 19-20: small meta
G 21-22(Y): acro - Describe dark chromo G bands
-
-later replication
-less are active in transcription
-condensed chromatin
-high A,T pairs
-stain light w/ rev. banding - List chromo abnormalities
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-Del
-Dup
-Inv
-Ins
-Iso
-R
-Recip. transloc.
-Rob. transloc - Define: Del,Iso, and Inv abnormalities
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del-loss of chromosomal material, is seen w/ FISH
i.e. typical Turner Syndrome, Cri-du-chat 5p,Prader-Willi 15s
iso- chromo w/ the same arms double dose of info on one arm & lack of on other i.e. form of Turners
inv- region is reoriented and same info is there only in a diff order,asymptomatic,poss. unbalanced offspring - Define: Dup,R
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Dup- 2 or more copies of the same region of the chromo, globin genes= species variation
R-loss of telomeres on both ends they stick together and cause instable cell division (mitotic too) - Cells for karyotyping
-
-adult:
bld cx 2-3d
bone marrow bx
fibroblasts cx 2-3w
-prenatal:
amniotic cells cx 2-3w
chorionic villus sample - FISH vs. Chromo painting
-
FISH-fluorescent probe hybridized to a metaphase chromo slide.w/ banding techniuqe assigns a gene to a specific chromo band
used for big genomic probes
Painting- diff colored fluorescent probes bind to chromos. distinguishes b/t chromos, detects aneuploidy in interphase - Numerical Abns
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nondisjunction=aneuploidy=wrong #of chromos=monosomy:lack of 1 chromo, only x mono will live
trisomy: 1 xtra chrom, only 21,18,13 live
polyploidy: 3-4 xtra chrom,none live - Trisomy 21
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Downs:47 xx/xy +21
-mental retardation
-specifically shaped head and feet
-heart defects
-1/700 live
-early alzheimers app gene on 21 - Trisomy 18
-
Edwards-47xx/y+18
-hypertonicity
-prominant occiput
-small chin
-rocker bottom feet
-heart defects
-porfound mental retardation
-1/8000
-80% female
-die w/in 1 yr - Trisomy 13
-
Patau-47xx/y +13
-sloping forehead
-forebrain defects
-eye abns
-cleft lip/palate
-polydactyly
-heart defects
-prof retardation
-deafness
-1/20000
-= sex
-die w/in 1 yr - Turner
-
45X0
-webbed neck
-short
- no 2ndary sex characteristics
-norm intelligence
-heart/renal defects
-1/2500-5000
-paternal meiosis error or post-conception error - Kleinfelter
-
47xxy
-low IQ
-low sperm ct.
-tall,long limbs,small testis
-gynecomastia
1/1000
-obesity,thyroid,pulmonary disease
-56% xtra maternal X
-inc gonadotrophin
TX w/ androgens - XXX
-
47xxx
-slight mental def
-additional barr bodies
-1/1000 - xyy
-
47xyy
-inc ht.
-dec IQ
-behavioral abns-prison - Cri-du-Chat
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-Del of chromo 5 short arm
-severe retardation
-microcephaly
-characteristic faces
1/20000-50000
-del not same for diff pt.s
- contiguous gene syndrome: lots of diff genes are deleted - Philadelphia chromo
-
-translocation b/t chromo 9& 22
-somatic
-abl gene on #9 inserts in bcr gene on #22 = CML - CML
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-fusion of abl & bcr
-presents in middle age
-initial phase:fatigue,nite sweats,fever
-enlarged spleen
-initial phase: lasts 1 mo.
-accelerated phase: bone pn.splenomegaly
-last phase: blast crisis blding & inf. b/c of bone marrow failure - Dx & Tx of CML
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DX:
-dec leukocyte AP
-bcr-abl fusion
Tx:
-urea intake eases symps
-interferon delays progression
-BM transplant
-STI571 inhibits bcr-abl activity controls disease early & improves advanced cases - SRY gene
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-if present on Y chromo = male gonad
-downstream genes=functional gonad - True hemaphrodite
-
-46xx,some w/ SRY
-some are mosaics or chimeras w/ 46xx or xy
-ovarian & testicular tissue
-rare
-mixed male & female characteristics
- - Female pseudo-hermaphrodite & causes
-
-ovaries w/male 2ndary characteristics
Causes:
-prenatal exposure to androgens or progesterone
-inherited deficiency of 11 or 21 hydroxylase needed for prod of corticosteroids not androgens
- causes adrenogenital syndrome - Adrenogenital syndrome
-
-1/10000
-in females early detection important
-males= premature puberty= masculinization
-hyperplasia of adrenal cortex
-severe hyponatremia & hyperkalemia
-tx w/ cortisol tells pituitary gland not to make ACTH and progestins are not diverted into androgen prod. - Male pseudo-hermaphrodites & cause A
-
-46xy
-externally female
-no female reproductive organs, but testes in abd (testicular feminization)
-presents w/ amenorrhea or infertility
-androgen receptor defect X-recessive - Male pseudo-hermaphrodites & cause B
-
-46xy
-partial feminization & birth
-virilization & puberty
-5 alpha reductase deficiency A-recessive=testosterone not converted to dihydrotestosterone