chromo abronmal

Question 1

how to Prepare karyotype

Answer 1

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

Question 2

dna is compacted around

Answer 2

histones futher condesed to Chromatin

Question 3

common chromosome features

Answer 3

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

Question 4

what stain causes the bands

Answer 4

Giemsa staining leaves a recognizable pattern of bands

can detect major chromosome abnormality

Question 5

what causes bands

Answer 5

Bands caused by differently staining

Question 6

how is increase in resalution measured

Answer 6

more bphs – bands per haploid set

Question 7

what are the darker areas

Answer 7

Dark (heterochromatin) more compact fewer genes

Question 8

light area

Answer 8

Light (euchromatin) more open more genes

Question 9

what phase are is karotype done

and why

Answer 9

Now often done prophase rather than metaphase

as the chromosomes are less compact so more detail

Question 10

another form of stain for karyotype

Answer 10

Karyotype fluorescent stain

can identify some forms of chromosmes abnormaility

Question 11

what is Aneuploidy

Answer 11

abnormal number of chromosomes

n

Question 12

what is meiosis and what is the function

Answer 12

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

Question 13

how does it ensure To ensure genetic variation in the gametes

Answer 13

Enables random assortment of homologues and recombination

Question 14

what is Non-disjunction

Answer 14

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

Question 15

when does it happen

Answer 15

occurs in meiosis 1 or 2

Question 16

what is results in

Answer 16

Always results in either +1 or -1 chromosome

When fertilized either trisomy or monosomy

Question 17

diff between m1 and m2

Answer 17

Meiosis I all daughter cells affected

or half in m2

Question 18

Why is s chromosome imbalance tolerated?

most common form og aneiploidy

Answer 18

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

Question 19

Why if inactivated does abnormal number X have effect

Answer 19

Both X and Y chromosome have PAR

PAR- pseudo-autosomal region

Question 20

x chromosme par

Answer 20

not inactived still produce genes

Question 21

Trisomy 21/down syndrome how

Answer 21

Most trisomy 21 arises in maternal non-disjunction

during maternal meioisis

Question 22

down syndrome vs age

Answer 22

Risk of maternal non-disjunction increases with age

higher chance of having baby with ds

Question 23

Why is there a maternal age effect

Answer 23

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

Question 24

what is oogenesis

Answer 24

Female non-disjunction

Question 25

why

Answer 25

Likely due to degradation of factors which hold homologous chromatids together

Question 26

Paternal Age Effect

Answer 26

Paternal Age not risk factor increased aneuploidy | Does affect a subset of single gene disorders

Question 27

Paternal role in aneuplody

Answer 27

Although no age effect some aneuploidy paternal | smoking a risk factor (not maternal)

Question 28

are aneuploidy captable with life

Answer 28

Most not compatible with life | s chromosome an exception

Question 29

when does cross over chromosome happen

Answer 29

Occurs in prophase I

Question 30

why

Answer 30

increases genetic diversity

Question 31

how

Answer 31

Pairs of chromosomes align | Chiasma form and crossover occurs

Question 32

can it go wrong

Answer 32

yes

Question 33

Unequal crossover

Answer 33

chromosome aligned incorrectly

Question 34

results in

Answer 34

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

Question 35

Single chromosome abnormalities

Answer 35

deletion duplication pancreatic inversion

Question 36

what is deletion

Answer 36

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

Question 37

what is duplication

Answer 37

Most often caused by unequal cross over

Question 38

pancreatic inversion | where happen

Answer 38

can happen around the centromere or in the middle

Question 39

are carriers effected

Answer 39

no

Question 40

cause

Answer 40

Can cause reproductive problems | Children with deletions/insertions

Question 41

Two chromosome abnormalities

Answer 41

transfer between non homolougous pair of chromosomes

Question 42

if uni directional transfer

Answer 42

insertion

Question 43

what is mutual exhange

Answer 43

swapped

Question 44

if balanced

Answer 44

does not affect carrier may cause problems in off spring

Question 45

what can it cause

Answer 45

can cause partial trisomy or monosomy

Question 46

can it occur in somatic cells

Answer 46

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

Question 47

Williams syndrome what type of mutation

Answer 47

deletion | 7q11.23 deletion

Question 48

what facial changes

Answer 48

Short, upturned nose | Arched eyebrows

Question 49

social changes

Answer 49

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

Question 50

can you detect it using karyotyping

Answer 50

no too small

Question 51

what to use instead

Answer 51

Can be detected using targeted FISH

Question 52

what cab you see

Answer 52

Lack of elastin on affected chromosome

Question 53

7q11.23 duplication syndrome | causes what facualy

Answer 53

Flat eyebrows | Broad nose and short philtrum

Question 54

social causes

Answer 54

Delayed speech development | Autistic behaviours that affect social interaction and communication

Question 55

what has a milder phenotype out of deletion and duplication

Answer 55

duplication

Question 56

what is meacentric

Answer 56

when the short and long arm are nearly the same length | ... centromere roughly in the centre

Question 57

submetacentric

Answer 57

short arm considerbly shorter than long arm

Question 58

acrocentric

Answer 58

short arm reduced down to a vistigle stump

Question 59

what are the acrocentric chromosoems in humans

Answer 59

``` 13 14 15 21 22 ```

Question 60

why are they special

Answer 60

they can undergo Robertsonian translocation | you form normal and deritive chromosome

Question 61

what can it cause

Answer 61

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

Question 62

Mosaicism

Answer 62

Presence of two or more populations of cells with different genotypes

Question 63

example.

Answer 63

X-inactivation results in mosaic expression

Question 64

Mosaicism can arise two mechanisms

Answer 64

Non disjuncture during early development | Loss of extra chromosome in early development