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Extra > chromo abronmal > Flashcards

chromo abronmal Flashcards

1
Q

how to Prepare karyotype

A 
collect peripheral blood
Isolate white cells
Culture in presence of phytohaemagglutinin
Stimulates T-lymphocyte growth/differentiation
After 48 hours add colchicine
Causes mitotic arrest – metaphase
Place in hypotonic saline
Place on slide 
Fix and stain
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2
Q

dna is compacted around

A

histones futher condesed to Chromatin

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3
Q

common chromosome features

A 
telomere at both ends 
centromere between both arms  
p-arm (short – petite) 
q-arm (long arm)
light and dark bands
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4
Q

what stain causes the bands

A

Giemsa staining leaves a recognizable pattern of bands

can detect major chromosome abnormality

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5
Q

what causes bands

A

Bands caused by differently staining

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6
Q

how is increase in resalution measured

A

more bphs – bands per haploid set

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7
Q

what are the darker areas

A

Dark (heterochromatin) more compact fewer genes

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8
Q

light area

A

Light (euchromatin) more open more genes

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9
Q

what phase are is karotype done

and why

A

Now often done prophase rather than metaphase

as the chromosomes are less compact so more detail

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10
Q

another form of stain for karyotype

A

Karyotype fluorescent stain

can identify some forms of chromosmes abnormaility

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11
Q

what is Aneuploidy

A

abnormal number of chromosomes

n

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12
Q

what is meiosis and what is the function

A

production of gametes
To achieve reduction from diploid (2n=46) to haploid (n=23)
To ensure genetic variation in the gametes

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13
Q

how does it ensure To ensure genetic variation in the gametes

A

Enables random assortment of homologues and recombination

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14
Q

what is Non-disjunction

A

Non-disjuncture results in uneven number of chromosomes in daughter cells.

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15
Q

when does it happen

A

occurs in meiosis 1 or 2

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16
Q

what is results in

A

Always results in either +1 or -1 chromosome

When fertilized either trisomy or monosomy

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17
Q

diff between m1 and m2

A

Meiosis I all daughter cells affected

or half in m2

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18
Q

Why is s chromosome imbalance tolerated?

most common form og aneiploidy

A

X-inactivation of excess X chromosomes
Only one X-chromosome active
Low gene content of Y chromosome

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19
Q

Why if inactivated does abnormal number X have effect

A

Both X and Y chromosome have PAR

PAR- pseudo-autosomal region

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20
Q

x chromosme par

A

not inactived still produce genes

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21
Q

Trisomy 21/down syndrome how

A

Most trisomy 21 arises in maternal non-disjunction

during maternal meioisis

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22
Q

down syndrome vs age

A

Risk of maternal non-disjunction increases with age

higher chance of having baby with ds

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23
Q

Why is there a maternal age effect

A 
Paused in utero in prophase I until puberty
Secondary oocyte arrests in metaphase II
Only competes if fertilized
One primary oocyte yields only one ovum
Finite number of primary oocytes
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24
Q

what is oogenesis

A

Female non-disjunction

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25
Q

why

A

Likely due to degradation of factors which hold homologous chromatids together

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26
Q

Paternal Age Effect

A

Paternal Age not risk factor increased aneuploidy

Does affect a subset of single gene disorders

27
Q

Paternal role in aneuplody

A

Although no age effect some aneuploidy paternal

smoking a risk factor (not maternal)

28
Q

are aneuploidy captable with life

A

Most not compatible with life

s chromosome an exception

29
Q

when does cross over chromosome happen

A

Occurs in prophase I

30
Q

why

A

increases genetic diversity

31
Q

how

A

Pairs of chromosomes align

Chiasma form and crossover occurs

32
Q

can it go wrong

A

yes

33
Q

Unequal crossover

A

chromosome aligned incorrectly

34
Q

results in

A

duplication/extra meterial in one chromosome and deletion in another chromosome

35
Q

Single chromosome abnormalities

A

deletion
duplication
pancreatic inversion

36
Q

what is deletion

A

Can be the result of unequal cross over
Breaks in chromosome
Can occur at ends

37
Q

what is duplication

A

Most often caused by unequal cross over

38
Q

pancreatic inversion

where happen

A

can happen around the centromere or in the middle

39
Q

are carriers effected

A

no

40
Q

cause

A

Can cause reproductive problems

Children with deletions/insertions

41
Q

Two chromosome abnormalities

A

transfer between non homolougous pair of chromosomes

42
Q

if uni directional transfer

A

insertion

43
Q

what is mutual exhange

A

swapped

44
Q

if balanced

A

does not affect carrier may cause problems in off spring

45
Q

what can it cause

A

can cause partial trisomy or monosomy

46
Q

can it occur in somatic cells

A

Can occur in Somatic cells cf Philadelphia chromosome t(9;22)(q34;q11) CML

47
Q

Williams syndrome what type of mutation

A

deletion

7q11.23 deletion

48
Q

what facial changes

A

Short, upturned nose

Arched eyebrows

49
Q

social changes

A

Friendly, social ‘cocktail party’ personality – an absence of social anxiety

50
Q

can you detect it using karyotyping

A

no too small

51
Q

what to use instead

A

Can be detected using targeted FISH

52
Q

what cab you see

A

Lack of elastin on affected chromosome

53
Q

7q11.23 duplication syndrome

causes what facualy

A

Flat eyebrows

Broad nose and short philtrum

54
Q

social causes

A

Delayed speech development

Autistic behaviours that affect social interaction and communication

55
Q

what has a milder phenotype out of deletion and duplication

A

duplication

56
Q

what is meacentric

A

when the short and long arm are nearly the same length

… centromere roughly in the centre

57
Q

submetacentric

A

short arm considerbly shorter than long arm

58
Q

acrocentric

A

short arm reduced down to a vistigle stump

59
Q

what are the acrocentric chromosoems in humans

A 
13
14 
15
21
22
60
Q

why are they special

A

they can undergo Robertsonian translocation

you form normal and deritive chromosome

61
Q

what can it cause

A 
Can cause problems in offspring 
most people are unaffected  
causes unbalanced chromosome causing down syndrom on c21 
or 
lethal
62
Q

Mosaicism

A

Presence of two or more populations of cells with different genotypes

63
Q

example.

A

X-inactivation results in mosaic expression

64
Q

Mosaicism can arise two mechanisms

A

Non disjuncture during early development

Loss of extra chromosome in early development

Extra (45 decks)

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