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32 Cards in this Set

  • Front
  • Back
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
-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
orders chromos in:
-position of centromere
Describe how non-banded chromos are grouped
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
-Recip. transloc.
-Rob. transloc
Define: Del,Iso, and Inv abnormalities
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
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
bld cx 2-3d
bone marrow bx
fibroblasts cx 2-3w
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
Reciprical-chromo breaks & rejoins @ a diff place on another chromo.carriers can be normal,but abn gametes can be made=affects mutiple genes=affects multi tissues.common symptoms,retardation,heart defects
Robertsonian- long arms of 2 acro chromos fuse. phenotypically norm but abn offspring
Numerical Abns
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
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
-prominant occiput
-small chin
-rocker bottom feet
-heart defects
-porfound mental retardation
-80% female
-die w/in 1 yr
Trisomy 13
Patau-47xx/y +13
-sloping forehead
-forebrain defects
-eye abns
-cleft lip/palate
-heart defects
-prof retardation
-= sex
-die w/in 1 yr
-webbed neck
- no 2ndary sex characteristics
-norm intelligence
-heart/renal defects
-paternal meiosis error or post-conception error
Tx of Turner
estrogen @ puberty for 2ndary sex characteristics
growth hormone for ht.
check for hidden y chromo poss malignancies
-low IQ
-low sperm ct.
-tall,long limbs,small testis
-obesity,thyroid,pulmonary disease
-56% xtra maternal X
-inc gonadotrophin
TX w/ androgens
-slight mental def
-additional barr bodies
-inc ht.
-dec IQ
-behavioral abns-prison
-Del of chromo 5 short arm
-severe retardation
-characteristic faces
-del not same for diff pt.s
- contiguous gene syndrome: lots of diff genes are deleted
Philadelphia chromo
-translocation b/t chromo 9& 22
-abl gene on #9 inserts in bcr gene on #22 = CML
-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
-dec leukocyte AP
-bcr-abl fusion
-urea intake eases symps
-interferon delays progression
-BM transplant
-STI571 inhibits bcr-abl activity controls disease early & improves advanced cases
SRY gene
-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
-mixed male & female characteristics
Mixed gonadal dysgenesis
-mosaic 46xy or 45xo
-mixed male & female characteristics
-male 2ndary characteristics @ puberty
Female pseudo-hermaphrodite & causes
-ovaries w/male 2ndary characteristics
-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
-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
-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
-partial feminization & birth
-virilization & puberty
-5 alpha reductase deficiency A-recessive=testosterone not converted to dihydrotestosterone