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EMs -GId > week 3 > Flashcards

week 3 Flashcards

1
Q

what is conventional cytogenetics

A

Metaphase chromosome analysis

G-banding

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2
Q

what is molecular cytogenetics?

A

cytogenic analysis at the molecular resolution at all stages of the cycle –> DNa or in situ

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3
Q

at what stage of the cell cycle is the chromsome most visible?

A

at the metaphase stage during mitosis –> this is around 15 minutes long

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4
Q

what is the G1 stage of cell cycle?

A

cellular content excluding the chromosome is doubled and this take 6-12 hours

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5
Q

what is the S stage of cell cycle?

A

each of the 46 chromosomes are duplicated –> 6 too 8 hours

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6
Q

what is the G2 stage of cell cycle?

A

the cell double checks the chromosome for any erros and makes repairs . 3 to 4 hours

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7
Q

how many bands are there on a chromsome?

A

550 –> there are bands within bands –> 30000 genes

each band has about 50 genes

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8
Q

explain the chromosome structure

A

centromere in the middle. Telemore at the ends. P is the short arm and Q is the long arm

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9
Q

types of cytogenic abnormalities?

A

numerical and structural

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10
Q

what signs can there be that someone has a cytogenic abnormalty?

A

organ malformation, falcial dysmorphism. Comprised mental and intellectual functioning –> however this has a longer onset time

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11
Q

what does diploidy mean?

A

two sets of chromosomes

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12
Q

what is aneuploidy?

A

the gain or loss of a chromosome

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13
Q

what is polyploidy?

A

this is the gain or loss of a whole set of chromosome

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14
Q

what increases the risk of errors at gametogenesis?

A

increase in age of paternal and materal, anueploidy

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15
Q

what is meiotic errors ( non disjunction)?

A

failure of chromosome or chromatid to seperate

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16
Q

what are the clinical features of trisomy 21?

A

Head
Eyes: upward slanting; brushfield spots
Nose: Small
Ears: abnormally shaped/low set
Tongue: protruding –> because mouth is small
General – flat face, brachycephalic, short neck
Neurological –> Learning disabilities (mild to moderate IQ 30-60)
Hands and feet
single palmar crease
short broad hands
5th finger clinodactyly
wide gap (sandal gap) between the 1st & 2nd toes

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17
Q

what are the statistics for trisomy 21?

A

1/700 birthds

75% spontaneously abort

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18
Q

what are the affects of trisomy 21 in adults?

A

fertility not affected for females but is for males.
life expectancy –> 55-658yrs old
medical problems
increase chance of certain cancers ( mainly leukaemia)
hypothyroidsm
alzheimers
obesity,ceoliac, arthritis, diabetes, hearing loss, seizures

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19
Q

what is trisomy 18

A

edwards syndrome
1 in 6000
95% spontaneous abort
only 10% live over the age of 1

20
Q

what are the clinical implications for the head for someone with trisomy 18

A

microcephaly, low set of ears, clift lip and palate, micrognathia

21
Q

what are the clinical features of the hands and feet for trisomy 18?

A

clenched hands –> very common, rockbottom feet and overalapping fingers

22
Q

what are the organ malformation for child with trisomy 18

A 
congential heart disease (90%) 
umbilical or inguinal hernia 
congential kidney abnormalities
mental retardation
short sternum
low birth weight
eye problems --> cataract and micrognathia
23
Q

what is trisomy 13?

A

Patue syndrome, 1 in 12000 live births and 95% spontaenous abortion

24
Q

what are the symptoms of patue syndrome?

A

mental retardation, small at birth, microcephaly and sloppping forehead, and also defects of the brain –> holoprosencephaly

25
Q

what are the phenotype features of trisomy 13?

A 
Eyes – microphthalmia, coloboma, retinal dysplasia, palpebral fissures slanted
polydactyly/ flexed fingers
abnormal genitalia 
heart defect
cleft lip and palate
ears abnormal and low
26
Q

when does female and male miosis begin?

A

females miosis begins as early as 5 months of development and finishes at puberty. However in males does not start till puberty

27
Q

what are the two steps that can causes autosomal aneuploidy for the prenatal fetus?

A

unfavourable chiasmata distribution (foetus)
and also age dependent deterioation of the fetus –> as the female gets older the more affect the enviroment such as radation, alcohol, drugs has on there uterus

28
Q

is the phenotype less affected in sex chromosome mutation or autosomal ones?

A

sex chromosomes

29
Q

what is the chromosome strcuture for klinefelter and Turners syndrome?

A

Turners is 45 (x) –> 1 in 2500

Klinefelter is 47 (XXY) 1 in 1000

30
Q

what are the features of turners syndrome?

A

reproductive –> loss of ovarian function, won’t go through puberty unless given some hormone treatment and infertility
lymphatics –> webbed neck–> swelling of hands or/& feet
other–> coarctation of aorta, short stature as she does not go through puberty –> IQ normally reduced compared to SIBs

31
Q

what is the diagnosis of klinefelter syndrome?

A

64% is not diagnosed –> usually diagnosed when they try have kids –> infertile or if they develop hypogonadism

32
Q

what affect will klinefelter syndrome have on infertility

A

May lack secondary sexual characteristics
Testicular dysgenesis
Reduction in sperm count
30-50% gynaecomastia (20x risk breast cancer)

33
Q

what is the growth and IQ of patients with kilinefelter syndrome ?

A

will be normal when a child but accelerate very quickly –> long arms and legs
IQ –> depends a lot on there family and also how many x’s they have

34
Q

what are the three causes of triploidy?

A

dispermy, digny, diplospermy

35
Q

what happens with double paternal in chromosomes numbers

A

promote large placeneta and some growth delay

36
Q

what happens with double maternal in chromsomes numbers?

A

tiny placenta, significant delay in growth and head-saving macrocephaly due to the small placenta

37
Q

what does the paternal and maternal sex chromosome code for?

A

maternal –> foetus and paternal –> placenta

38
Q

what is mosaicism ?

A

it is miototic non disjunction

39
Q

what is reciprocal translocation?

A

when two parts of different chromosomes swap –> 1 in 500 chance. 5-10% phenotype risk
reproductive risk

40
Q

what the acrocentric chromosomes?

A

13,14,15,21 and 22 –> shorter chromosomes

41
Q

what is robertsonian translocation?

A

it is when 2 acrocentric chromosomes come together and the long q arms join together and discard of the short arms

42
Q

what is unbalance rearrangment?

A

the gain or loss of huge amount of chromosomes/DNA –> can cope with gain a lot better than loss. It is usually sporadic and can be due to deletion or duplication

43
Q

what is . Interstitial deletion?

A

when a section of a chromosome is lost

44
Q

what is terminal deletion?

A

when a chuck of chrosome is lost from teh terminal ends

45
Q

what is duplication of a chromosome?

A

when a section of the chromosome is duplicated

46
Q

what is a ring chromosome?

A

when bits of either end of the chromosome breaks and forms a ring

EMs -GId (7 decks)

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