Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

MCG > LEC42: Inborn Errors of Development: Chromosomes and Cytogenetics > Flashcards

LEC42: Inborn Errors of Development: Chromosomes and Cytogenetics Flashcards

1
Q

cytogenetics?

A

study of chromosomes

mechanisms of chromosomal disorders (microscopic & submicroscopic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what proportion of 1st trimester spontaneous abortions do chromosome abnormalities cause?

A

2/3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what % of cardiac defects do chromosome abnormalities cause?

A

20% of pts w/ cardiac defects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what % of individuals w/ intellectual disability have a chromosomal abnormality?

individiuals w/ autism and cardiac defects?

A

intellectual disability: 20-30%

autism, cardiac defects: 20% each

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

characteristics to identify chromosomes?

A

size, banding pattern, position of the centromere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how are chromosomes numbered?

A

based on length, 1 is longest, 22 should be shortest (actually, 22 is longer than 21)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

chromosome nomenclature:

short arm?

A

p

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

chromosome nomenclature:

long arm?

A

q

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

chromosome nomenclature:

region?

A

counting outward from centromere

within each region, have bands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

chromosome nomenclature:

landmark?

A

consistent & distinct morphologic features

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

chromosome nomenclature:

bands?

A

division of regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

centromere is?

telomere is?

A

centromere: central condense region essential for itotic spindle attachment
telomere: terminal cap at end of each chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does p11.1 mean

A

p is short arm

1 is chromosome

2nd is region

3rd is subband

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

name parts of the chromosome/their function

A

short arm: p

long arm: q

telomere: cap/end of chromosome, helps chromosome keep its integrity; shortens with aging

subtelomeric region: region most prone to errors of deletions and duplications

center: centromere; different centromere locations can characterize diff chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

metacentric vs. sub-metacentric vs. acrocentric chromosome?

A

metacentric: centromere in middle of equal p and q arms

sub-metacentric: p short, q longer

acrocentric: p arm essentially a satellite, doesn’t do much

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are dark/light bands on chromosomes?

A

dark: heterochromatin, inactive in transcription, not expressed, long repeats of many genes, thus more variable regions
light: euchromatin, more active txn area, where most active genes and crucial human disease genes are

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

which chromosomes have large heterochromatic regions?

A

1, 9, 16, Y

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

which chromosomes are acrocentric?

A

13, 14, 15, 21, 22

p arm is a satelle, nub, does not have important function - could lose satellite to no consequence for function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

when in cell cycle can chromsomes be visualized?

A

metaphase

during active division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

which cell types provide easy chromosome visualization?

A

dividing cells, in mitosis of cell cycle:

**T lymphocytes in blood which divide by phytohemagglutinin **

bone marrow cells

**fibroblasts from skin biopsies **

prenatal chorionic villi and fetal cells in amniotic fluid

products of conception (placental & fetal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

in what part of cell cycle do cells spend most of their time?

A

interphase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how long is cell cycle?

mitosis?

A

cell cycle: 24 hours

mitosis: 1-2 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is chromosomal imbalance?

when is it most common?

A

imbalane in the amount of chromosomal material; may involve a few to 1000s (partial/whole chromosome) of genes, have catastrophic effects

most common in spermatogenesis, oogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

how can chromosomal imbalance mainfest?

A

1) whole or partial aneuploidy: gain or loss of a whole chromosome
2) abnormality may be in constitutional, non-mosaic, or mosaic state, which is less severe, = various chromosome complements in different cells
3) monosomy - one missing - is more devastating than trisomy - one extra

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
clinical phenotypes of chromosomal abnormalities
1) development delay/intellectual disability 2) alteration of facial morphogenesis to produce characteristic facial features 3) growth delay 4) malformations of internal organs - esp. cardiac
26
general effects of structural and numerical abnormalities - how do 1) loss of genetic material, 2) gain of genetic material, 3) relocation manifest?
1) loss of genetic material: deletion/monosomy 2) gain of genetic material: duplication/trisomy 3) relocation of genetic material: inversion/insertion/translocation
27
first trimester abortuses are mostly what kind of abnormality? what kind of chromosomal abnormality dominates when fetus is born?
1st trimester: numerical - extra or missing chromosome, not structural issue when fetus born: balanced/unbalanced abnormalities
28
why do chromosomal abnormalities occur more commonly in older than in younger women?
their eggs have been "frozen in time" for longer error of nondisjunction more common when oocyte has been suspended for long time
29
what is most common cause of spontaneous abortions? what trisomy is observed w/ this?
chromosomal imbalance causes 66% 1st trimester spontaneous abortion, 20% 2nd trimester spontaneous abortions trisomy 16 most common trisomy observed; never seen in liveborn (except if mosaic)
30
ploidy?
addition or loss of **complete sets **of chromosomes
31
euploidy?
normal diploid chromosomal state
32
triploidy? its cause? what happens?
1 complete extra set of chromosomes caused by polyspermy, fertilization of an egg by more than 1 sperm usually spontaneously abort digyny: extra haploid set is fro mmother; get IUGR, v. small placenta diandry: extra haploid set is from father; get well grown fetus and large cystic complement
33
tetraploidy? cause? what happens?
egg fertilized by 2 sperm failure of first (early) zygotic division lethal to embryo other cell divisions may also fail to complete properly; small proportion of tetraploid cells can be in norma individuals (mosaicism)
34
what are autosomal numerical abnormalities?
aneuploidy, monosomies, trisomies
35
aneuploidy?
chromosome changes that don't involve whole sets usually consequence of failure of single chromosome (or bivalent) to complete division problem in chromosomal copy number
36
monosomies?
only 1 chromosome present in pair all are lethal in early embryogenesis; abort too early to be recognized as conception
37
trisomies? what is risk factor for it?
meiosis I nondisjunction causes this 3 chromosomes instead of 2 incidence of trisomes rises sharply w/ increasing maternal age
38
which full non-mosaic aneuploides are survivable?
trisomy 13 trisomy 18 trisomy 21
39
what is nondisjunction?
disjunction: when chromosomes are paired off in middle, split, make 2 gametes NON disjunction: chromosomal material stuck, 1 gamete has extra chromosome material, leads to a trisomy
40
what causes trisomy 21
95% caused by **maternal meiosis I nondisjunction ** 5% by parent carrying a Robertsonian translocation or mosaicism for Trisomy 21 75% spontaneously aborted
41
if child has trisomy 18, what kind of gene do they have for it?
must be mosaic otherwise too severe = edward's syndrome
42
what is more common: sex chromosome or autosome aneuploidies?
sex chrom aneuploidies are more common and less severe than in autosomes b/c of X-inactivation and paucity of genes on Y chromosome
43
what is X-inactivation
when females turn off/silence 1 copy of genes on one X chromosome makes gene dosage of X chromosome similar in males & females
44
what are pseudoautosomal regions
genes on X-chromosome that're also present on Y chromosome these escape X-inactivation occurs in: turner syndrome, klinefelter syndrome
45
what is cause of turner syndrome? incidence? phenotype?
numerical abnormality causing 45,X - missing an X very common, but 99% spontaneously aborted phenotype: nondysmorphic mostly; coarctation of aorta; kidney issues; haplo insufficiency
46
treatment for turney syndrome?
growth hormone & estrogen
47
what causes most turner syndrome? what are diff cytogenetic possibilities?
80% due to paternal meiotic error 45, X 50% 45,X/46,XX or 45,X/46,XY MOSAICS 30-40% structural X abnormalities 10-20%
48
what is cause of klinefelter syndrome? cause?
47,XXY pseuatosomal region abnormality problems w/ testicular function, decreased sexual characteristics, little spermatogenesis, ADHD
49
what are 47,XYY males and 47,XXX females
examples of numerical abnormalities of sex chromosomes both are essentially "normal"
50
what is \>3 copies of X chromosome associated w?
mental retardation
51
uniparental dipoidy? results?
when all chromosomes are inherited from 1 parent if paternal: hydatidiform moles; only get trophoblast hyperplasia, no fetal parts if maternal: from an activated unovulated oocyte; get ovarian tetroma, disorganized embryonic material
52
uniparental disomy?
when person receives 2 copies of a chromosome, or of part of a chromosome, from 1 parent, and 0 copies from the other parent affects single pair of chromosomes usually causes problems in imprinted genes on specific chromosomes (6, 7, 11, 14, 15, 16) usual cause is **trisomy rescue**
53
what is trisomy rescue?
when fertilized ovum containing 3 copies of a chromosome loses 1 of these chromosomes to form a normal, diploid chromosome complement if both retained chromosomes came from same parent, get univparental disomy
54
types of structural rearrangements?
1) translocation 2) inversion 3) deletion/duplication 4) ring chromosome
55
translocation?
interchange of genetic material between nonhomologous chromosomes can be **reciprocal/balanced**: no phenotype usually, only phenotype if have **disruption in break point** **unbalanced**: parital monosomy or partial trisomy - missing or extra piece
56
what happens in a translocation carrier?
whereas normally sister chromatids line up as bivalent and then get normal chromosome segregation, translocation carriers form a **tetrad** of chromosomes during separation or disjunction, get unbalanced translocation
57
what are adjacent 1 and 2 outcomes?
outcomes of translocation carrier chromosome segregation adjacent 1: unbalanced translocatoin adjacent 2: centroemres from the same chromosome
58
robertsonian translocation?
translocation between different acrocentric chromosomes (13 to 14, for ex) short arms are lost, long arms fuse at centromere occurs in 5% of Down Syndrome cases considered **balanced** b/c no missing chromosomal material!
59
inversions? types?
2 breaks in 1 chromosome area between the breaks is inverted, then reinserted, the breaks unite then to rest of chromosome; can be **terminal-** to end of chromosome, or **interstitial**- within the long or short arm **pericentric inversion: **if inverted area includes centromere **paracentric inversion**: if inverted area doesn't include centromere can cause deletions, duplications
60
what do inversions cause?
deletions, duplications
61
deletion is?
loss of a chromosome segment can be interstitial or terminal
62
wolf-hirschhorn syndrome is ex. of?
deletion of 4p16.3
63
ring chromosomes?
when pieces on top of chromosmoe fall off, join into a ring shaped chromosome Ring X r(X) is most common, causes Turney syndrome in most cases
64
"viable" chromosome imbalances?
unbalanced translocations: partial monosomy & partial trisomy deletions: partial monosomy duplications: partial trisomy ring: partial monosomy recombinant inversion derivatives: partial monosomy & partial trisomy
65
what is FISH
FISH = flourescence in situ hybridization physical DNA mapping technique DNA probe labeled w/ marker molecule is hybridized to chromosomes on a slide, visualized using flourescence microscope marker molecule is floursescent or detected w/ fluourescently labeled antibody
66
FISH hybridization steps?
denature ds DNA, generate single-stranded DNA probe w/ fluorochrome DNA probe of bases probe recognizes target DNA sequences probe hybridizes to target DNA sequences
67
FISH applications?
chromosome identification aneuploidy detection in prenatals marker chromosome identification total chromsome analysis translocation analysis microdeletion syndrome analysis gene amplification analysis in cancer
68
what is FISH used to study?
good to est. deletion, duplication of genomic regions too small to be detected by karyotype analysis particularly: recurrent microdeletion syndromes caused by unequal crossing over events at susceptible regions of the genome confirmation, not diagnosis of genomic disorders involving microdeletion/duplication syndromes ie DiGeorge Syndrome - deletion of single gene on 22q11 or Wilms tumor, caused by deletion of series of adjacent genes on 11p13
69
cause of DiGeorge/Velo-cardio-facial syndrome?
22q11 deletion
70
array CGH usefulness? what isn't it good for?
**genome-wide view of copy number variations ** helps to **find cause for selected conditions** ie of intellectual disability and multiple congenital anomalies; standard of care used rather than karyotype cannot detect chromosomal anomalies that mintain normal copy numer (balance translocation, inversions); does not provide data on repeat-rich regions (centromeres, hterochromatin)
71
what is meiosis?
meiosis I: process by which recombination of chromosomes occurs in germ cells meiosis II: yields mature haploid oocytes and spermatogonia
72
why do trisomies/monosomies occur?
failure to properly segregtae chromosomes during each division step of meiosis leads to abnormal copy number in resulting conceptus
73
are autosomal numerical abnormalities viable? why/why not?
usually, not because large alterations in gene dose occur
74
what causes most trisomies?
95% trisomies are due to meiotic non-disjunction 75% occur during meiosis I

MCG (77 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions