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ANAT 381 > Aneuploidy > Flashcards

Aneuploidy Flashcards

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1
Q

what is normal conceptus

A

haploid gametes produces diploid normal conceptus - spermatozoon plus ovum = conceptus

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2
Q

what is chromosome abnormality

A

Aneuploidy = chromosome segregation goes wrong = 2 types, 2n +1 or 2n-1

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3
Q

describe aneuploidy

A

trisomy/monosomy

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4
Q

describe haploidy

A

one set of chroms

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5
Q

describe polyploidy

A

more than 2n chroms (triploidy, tetraploidy etc)

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6
Q

describe chromosome rearrangements

A

could be translocations, deletions, inversions, duplications

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7
Q

what is maternal age effect in human reproduction

A

direct correlation between age and female repro
females become pregnant at any age = risk of chrom problem but risk goes up as age

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8
Q

what is paternal age effect in human reproduction

A

limited study
associations = older = more likely to produce autistic children and also children with more gene defects

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9
Q

name origins of chromosome abnormalities

A

gametogenesis errors
fertilization
Embryogenesis

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10
Q

describe gametogenesis - origin of chromosome abnormality

A

= m1 and m2
oogenesis
spermatogenesis

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11
Q

describe fertilization - origin of chromosome abnormality

A

dispermic fertilization
digynic fertilization after icsi
parthenogenic activation/chimera

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12
Q

describe embryogenesis - origin of chromosome abnormality

A

mitotic error

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13
Q

describe female - divisions involved in formation of embryo

A

Prophase: after DNA replication, homologous chromosomes pairing, synapsis and recombination, and arrest at the diplotene (dictyate) stage.
Oocyte remain arrested until puberty-follicular growth -LH surge triggers ovulation and resumption of m1 in preovulatory follicle
ovulated egg arrest at MII stage until fertilization - complete MII division

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14
Q

describe male - divisions involved in formation of embryo

A

Mammalian spermatogenesis is an androgen-dependent developmental process. It is driven by interactions between germ cells and somatic cells. Generates a continuous supply of functional sperm and it begins at puberty

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15
Q

describe meiosis 1 - non disjunction

A

one of mechanisms where chrom segregate goes wrong
= trisomy and monosomy

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16
Q

describe normal chrom segregation in meiosis 1 and after fertilization

A

normal, before = each cell has one set chrom and one set chrom in polar body (opp = switch chrom)
after fert = 2n (chromosomes can differ, what is in polar bodies vs oocyte)

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17
Q

describe nondisjunction chrom segregation in meiosis 1 and after fertilization

A

before = can result in disomic (2 chroms in oocyte, none in polar body), or nullsomic (all chroms in polar body)
after fert = trisomy or monosomy

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18
Q

describe predivision of one univalent in meiosis 1 and after fertilization

A

before = instead of dividing at same time = sister chromatids separate early = 23 +1/2 (one full plus half in oocyte, and half in polar body) or 22+ 1/2 (half in oocyte, 1+1/2 in polar body)
after = trisomy or monosomy

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19
Q

describe predivision of both univalent in meiosis 1 and after fertilization

A

before = leads to balanced m2 oocyte but still mistake tho
after = balanced egg, 2n

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20
Q

what is pssc

A

premature separation of sister chromatids

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21
Q

describe meiosis 1 errors

A

recomb failure
premature homologue separation
true nondisjunction
premature sister chromatid separation

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22
Q

describe meiosis 2 errors

A

Nondisjunction
premature sister chromatid separation

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23
Q

describe Aneuploidy in humans: estimated levels at different stages - eggs

A

eggs or polar bodies
karyotyping = 19902, 10-35%
fish = 1990s-present, 20-70%
cgh, snp array, cgh array= 2000s-present, 30-70%
ABNORMALITIES IN EGGS QUITE HIGH

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24
Q

describe aneuploidy in sperm

A

non disjunction - due to mistake in reduction division
if pssc = disomic 2, normal 1 and nullsomic 1 spermatozoa
if true nondisjunction = disomic 2 and nullsomic 2 spermatozoa

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25
describe Aneuploidy in humans: estimated levels at different stages - sperm
karyotyping 1980s-1990s, 1-4% fish = 1990s-present, 1-3% low in sperm = 1-4% millions of sperms in ejaculate so much study large numbers of sperm cells in one person (opposite problem for egg, )
26
name all techniques used to detect chromosome abnormality in eggs, sperm and embryos
* Karyotype * Fluorescence in situ hybridization (FISH) * Whole chromosome painting (SKY) * Comparative genome hybridization (CGH), Array CGH, SNP array (chip based) * Next Generation Sequencing (NGS)
27
describe metaphase karyotype -gen
5-10ml blood, and will process culture, arrest cells at metaphase stage then see of any issues gold standard even now
28
describe metaphase karyotype -sperm
studying sperm not easy = take hamster egg and human sperm and inject and wait for it to condense and see when reach metaphase and then can do G-banded human sperm chromosome spread after ICSI of hamster oocytes= can see sperm chroms since hamsters ones have diff shapes and sizes
29
describe karyotype of pb and m2 oocyte
m2 oocyte metaphase shows extra marker = tetrads 2nd polar body karyotype = except haploid cells, very different to get good spread, not best for clinical cases in eggs
30
what is fish - describe
most common for sperm want to find out if 1 or 2 copies of chrom 2 = probe dna complementary to chrom 2 (somewhere on whole chrom) then label with fluorescent dye, = red fluorochrome then denature and hybridize and do metaphase spread = lights up chroms
31
describe interphase nucleus
most cases = count colour = know which fluorochrome attached to each chrom e Especially in preimplantation embryo
32
describe fish on sperm
label x and y diff colours and see for diff chromosomes one = abnormal see x and y = xy18, should be haploid tho, if sperm fertilize normal egg = get xxy aneuploidy
33
name and describe Four methods used for detection of chromosomal copy number variation
fish comparative genome hybridization array cgh (chip based, need to analyze chromosome complement in sample) snp microarray
34
what is principle of cgh/acgh
Biopsies cells - dna and then do whole genome amplification label control dna with red label biopsy dna with green = unknown combine and gives yellow 2 results possible = metaphase cgh = see if colours correct, yellow = normal, more red = 2:1 monosomy, 2:3 more green = trisomy or do array cgh= use computer to analyze
35
describe fertilization errors - dispermic
3 pronuclei sperm brings abnormality or fertilized by 2 sperms = triploidy, 3 sets chroms
36
describe fertilization errors - digynic triploidy
especially with icsi separation of polar body = instead of becoming diff cell= retained 3rd pronuclei
37
describe mitotic error during embryogenesis
affects chrom composition
38
describe chromosome compositions in preimplantation embryos - 3 types
Normal = all euploid Abnormal = all aneuploid Mosaic = mix of both
39
describe chromosome compositions in preimplantation embryos -DESCRIBE abnormal
Aneuploid = trisomy/monosomy polyploid = more than 2n haploid = one set of chroms chaotic = random loss or gain of chroms
40
what does mitotic error do
generated mosaic embryo Embryo develops fast after fertilized = 70-100 cells after 5 days not proper cell cycle checkpoint = leads to mosaic, could also happen at later stages more normal blastocyst cells if error early
41
what is mosaicism
Mosaicism is the presence of one or more genetically distinct cell lines within an individual/embryo.
42
how to generate mosaicism = 2 ways
Post zygotic error in an originally diploid zygote Post zygotic error in an originally aneuploid zygote
43
describe Post zygotic error in an originally diploid zygote - trisomy 21
non disjunction during division = leads to 45,-21 and 47+21 and 2 46, n normal monosomy lost so embryo has normal and abnormal for trisomy 21, 46n, 47+21 MIX OF CELLS
44
describe Post zygotic error in an originally aneuploid zygote
starts with 47+21 abnormal zygote trisomy 21 during division = anaphase lag so loss of one chrom so it corrects itself Embryo mix of 46 n and 47+21
45
explain uniparental disomy conceptus
Abnormal oocyte + normal gamete from other parent = trisomy conceptus if corrects early = gets rid of one chrom- could get rid of one from dad, so now the 2 chroms are both from mom depends on which chrom= if has imprinted genes = can cause issues for implantation and live birth
46
how can we analyze embryos - diagnosing chromosome composition
spreading of nuclei on glass slide = interphase nucleus and label and see if normal or abnormal can also use fish
47
describe fish results - analyzing embryos
large portion of embryos mosaic like 47%
48
describe mosaicism throughout preimplantation development
randomly took human embryos (must ask patients first, ethics board, after ivf, hard to do), frequency of mosaic embryos heavily increased as move to blastocyst 2 or more distinct cell lines = mosaicism but the embryos make normal babies
49
describe type of mosaicism
2-4 cell = mostly diploid aneuploid and diploid chaotic, continues untill morula but by time reach blastocyst = diploid polyploid or diploid aneuploid
50
describe proportions of polyploid cells in blastocysts - good quality
polyploid cells important for invasion of endometrium during implantation normal = have fewer percentage of polyploid cells
51
describe proportions of polyploid cells in blastocysts - poor quality
higher % of polyploid cells if fetus tetra or triploid = miscarriage still do not know what % is normal or abnormal
52
describe Mixoploidy in Blastocysts of Domestic Species
Present in many animals - domestic species
53
Mechanism of mitotic error in embryos - what causes gains and losses
non disjunction anaphase lag Chromosome demolition chromsome replication
54
Mechanism of mitotic error in embryos - what causes losses alone
anaphase lag Chromosome demolition
55
Mechanism of mitotic error in embryos - what causes gain and loss for same chromosome
non disjunction
56
describe overall chromosome abnormality in embryos from older women
were much higher than younger patients
57
when is mosaicism present
mosaicism is present throughout the pre-implantation development
58
describe chaotic embryos
chaotic embryos are higher in poor quality embryos compared to good quality embryos
59
what increases with advanced maternal age
Aneuploidy rate increases with advanced maternal age
60
when does chromosome mosaicism have effects
only during preimplantation embryo dev and it has no clinical implications post implantation
61
describe significance of abnormal cells - 4
Abnormal cells are lethal - could be but depends on % of polyploid, most cells with chaotic = arrest Abnormal cells are loss = not necessarily true, depends on % cells left Abnormal cells become allocated to te = yes, did mouse studies, if make chimera (tetra + normal cells) = all tetra goes to te Abnormal cells co exist
62
describe pathogenesis of chromosomal mosaicism and its effect on early human dev - gen
~15 weeks amniocentesis or chorionic villi sample and see what cells are like
63
describe pathogenesis of chromosomal mosaicism and its effect on early human dev - 3 types
fetus mosaic placenta normal confined placental mosaicism = fetus fine but issues with pregnancy both fetus and placenta mosaic
64
describe pathogenesis of chromosomal mosaicism and its effect on early human dev - post zygotic trisomic rescue through placental mosaicism
postzygotic chromosome loss = leads to 2 possibilities non mosaic trisomic fetus + mosaic placenta with confinement of diploidy to trophoblast or trisomic placenta and non moasic diploid fetus happens in embryos but corrected *uniparental disomy = baby has some issues but mostly fine - diploid baby
65
what will post fertilization mitotic error result in
in constitutional chromosomal mosaicism - the mechanism by which it arises is not fully understood.
66
what does distribution of mosaicism in conceptus depend on
timing, cell lineage(s) involved, cell viability, and chromosome involved
67
describe origin of mosaicism - 2
meiotic or mitotic origin Meiotic mosaicism often have adverse effect on the conceptus such as trisomy zygote rescue, due to the presence of uniparental disomy in the embryo/fetus and/or due to dysfunction of a trisomic placenta
68
what can mosaicism be
tissue specific normal karyotype in lymphocytes does not exclude the presence of mosaicism elsewhere in the conceptus
69
what is main cause of infertility
due to pregnancy wastage due to chrom abnormality
70
describe chromosomal imbalance and pregnancy loss - reasons
Trisomies Monosomies Triploidies Multiple Aneuploidies Tetraploid and structura
71
describe trisomy 16
most common trisomy observed in product of conception studies never seen in live born advanced mat age, always loss, non viable
72
describe trisomy 21 and 22
next most common 2 = equally as common
73
describe survivable chromosomal imbalance
only a few full non-mosaic aneuploidies are observed in live-born apart from sex chromosome abnormalities For example: Trisomy 21, Trisomy 13, Trisomy 18...
74
describe trisomy 21
diagnose by checking blood = use peripheral blood standard 47, xy+21 down syndrome most still birth or features of down syndrome
75
describe trisomy 21 - medical issues
many issues cannot see what problems embryo will have even tho can see chrom abnormality Gastrointestinal obstruction -3% Respiratory infections = Common Leukemia = 15-20 X Congenital heart defect - 40% Moderate to severe mental retardation - 100% Development: Early intervention program
76
describe trisomy 18
47,xy+18 edwards syndrome possible live birth, most lost under 46 = probably die or sex chrom issue, above 46= bad news generally
77
describe trisomy 18 - medical features
exhibiting characteristic facial features, short sternum, overlapping fingers with clenched fists, and clubfoot probably wont live long
78
describe trisomy 13
47, xy,+13 patau syndrome live birth autosomal trisomies = severe
79
describe trisomy 13 - medical features
holoprosencephaly = defects, probbaly never take babies home, 6m-12m Defect of the brain, affects facial features, causing closely spaced eyes, and sometimes cleft lip and palate
80
name sex chromosome abnormalities - 4
* Turnersyndrome(XO) * Klinefeltersyndrome(XXY) * TripleXormore(XXX/XXXX..) * XYY
81
what is only monosomy to go to live birth
TURNER SYNDROME XO
82
what are some effects of turner syndrome
short stature-broad chest -low hairline -low set ears -small fingernails -characteristic facial features -poor breast development -ear infections and hearing loss -high waist to hip ratio (hips are not much bigger than the waist) Approx. 99%of all fetuses with Turner syndrome results SA - first trimester -Affects 1 in every 2,500 girl
83
describe turner syndrome
only about 1%, 45x survive, 99% do not survive (lost through spont abort) Hook and Warburton hypothesis that most surviving ones are ‘cryptic’ mosaics Rescue cell line may have viable karyotype= cells correct = possibility of normal cells somewhere, in some cells but not all, peripheral blood shows xo thp
84
what is klinefelter syndrome
47, xx7 probable cause = xx oocyte + y sperm or x oocyte + xy sperm
85
what is klinefelter syndrome - x inactivation
Most genes from the extra X undergo inactivation, but some escape and serve as the putative genetic cause of the syndrome
85
what is klinefelter syndrome - who it affects
Affects one in 660 men
86
what is klinefelter syndrome - phenotype
from "near-normal" (no intellectual issues) to a significantly affected individual
86
what is klinefelter syndrome - syndrome characterized by
varying degrees of cognitive, social, behavioral, and learning difficulties and in adulthood additionally primary testicular failure with small testes, hypergonadotropic hypogonadism, tall stature, and eunuchoid body proportion
87
what is klinefelter syndrome - when diagnosed
Most of them diagnosed later in life – mostly during fertility work up
87
what is klinefelter syndrome - infertility
47,XXY is identified in 11% of azoospermic men and in 3% of infertile men and thus represents the most common genetic cause of infertility no sperm in ejaculate, maybe one = if mosaic = find some sperm
88
what is klinefelter syndrome medical treatment
Medical treatment is mainly testosterone replacement therapy to alleviate acute and long-term consequences of hypogonadism most only realize when trying to make fam
88
describe 47, XYY male fertility
Most males with 47,XYY syndrome have normal sexual development and are fertile some may be fine, fertile no repro issues
88
describe 47, XYY male - who
Affects -1 in 1,000 newborn boy
89
describe 47, XYY male - syndrome associated with
an increased risk of learning disabilities, delayed development of speech and language skills. Delayed development of motor skills (such as sitting and walking), weak muscle tone (hypotonia), hand tremors or other involuntary movements
89
describe 47, XYY male - small percent
A small percentage of males with 47,XYY syndrome are diagnosed with autistic spectrum disorders
90
describe 47, XYY male twin brothers
two twin brothers. The shorter has a normal XY chromosome complement. The taller one has an XYY complement
90
What is the possible mechanism in generating this extra Y-chromosome in non mosaic males? -47, XYY
parental nondisjunction at m2 resulting in extra y chromosome yy sperm + x oocyte = xyy male
91
describe Post zygotic error in an originally diploid zygote - triple xxx
non disjunction = 45,x 47,xxx 46,xx 46,xx cell lines survive = individual is mix of alll

ANAT 381 (24 decks)

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