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GIM > Cytogenetics (Chromosomal) > Flashcards

Cytogenetics (Chromosomal) Flashcards

1
Q

What phase of mitosis are the Chromosomes most visible?

A

Metaphase

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2
Q

What are the ends of chromosomes known as?

A

Telomeres

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3
Q

The short arm of the chromosome is also know by which letter?

A

P

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4
Q

The long arm of the chromosome is also known by which letter?

A

q

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5
Q

Approximately how many genes and bands make up a karyotype?

A

550bands 30kGenes

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6
Q

Is loss or gain of chromosomes worse?

A

Loss

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7
Q

What is position effect?

A

Chromosome in new environment will function differently = different phenotype

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8
Q

Is sex chromosome or autosome imbalance worse?

A

Autosome imbalance is more severe

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9
Q

What does aneuploidy mean?

A

Gain or loss of chromosomes

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10
Q

What is mosaicism in terms of karyotype/cells?

A

Some are diploid (normal) and some have aneuploidy!

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11
Q

An increase in maternal age can increase the likelihood of what?

A

Aneuploidy

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12
Q

An increase in paternal age can increase the likelihood of what?

A

Nothing (well no aneuploidy)

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13
Q

In meiosis when are the chiasmata visible?

A

Metaphase I

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14
Q

In meiosis when are the chromosomes separated?

A

Anaphase I

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15
Q

What happens in meiosis II?

A

Mitotic division of the secondary gametocyte - Chromatids separate = mature sex cell produced

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16
Q

What is non disjunction?

A

A meiotic error

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17
Q

When does most non-disjunction occur (%) ?

A

Meiosis I (80-90%)

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18
Q

In trisomy one you are at greater risk of what?

A

Leukaemia, hypothyroidism, alzheimers + more

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19
Q

Which of males of females are usually infertile with trisomy 21?

A

Males

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20
Q

What percentage of trisomy 21 foetus’s spontaneously abort?

A

75%

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21
Q

What is the risk of trisomy 21 at a normal age?

A

1/700

22
Q

Trisomy 18 is called what? risk and spontaneous abortion stats?

A

Edward’s syndrome, 1/6000 95% spontaneous abortion

23
Q

Features of Edward’s syndrome

A

Short lifespan, microcephaly, sort sternum, low birth weight

24
Q

Most common organ abnormality in trisomy 18?

A

Congenital heart disease (90%

25
Q

Trisomy 13 stats?

A

Patau syndrome, 1/12000 (95% spont abort)

26
Q

features of trisomy 13?

A

Small eyes, cleft lip and palate, polydactyly-fingers flexed heart defects - severe retardation

27
Q

Why is trisomy 13, 18 and 21 more commonly seen than others?

A

Small chromosomes- others tend to be lethal although these do have high rates of abortion

28
Q

At what age do female ages start and remain at Meiosis I ?

A

5 months, suspended until puberty

29
Q

Karyotype of turner’s syndrome?

A

45X (affects females)

30
Q

Fertility issues with turners syndrome?

A

Infertility, no ovarian function or puberty

31
Q

Lymphatic issue of Turner’s?

A

Webbed neck, swollen feet

32
Q

Turner’s syndrome causes what structural problems?

A

Coarction of aorta, and short stature

33
Q

What is a common reason for diagnosis of klinefleters?

A

Inferitlity or Agenesis of sperm!

34
Q

Stature of klinefelter’s ?

A

Tall, long arms and legs!

35
Q

Klinefelter’s has a high risk of what cancer due to what?

A

Due to gynaecomastia 20X risk of breast cancer

36
Q

What is Digyny?

A

A diploid egg

37
Q

Double maternal contribution gives what?

A

Big head!!

38
Q

Double paternal contribution?

A

Foeutus many abnormalities, cystic placenta

39
Q

contribution of dad = what and mum = what?

A 
Mum = head 
Dad = Placenta
40
Q

Molar pregnancy is what?

A

Conception but not embryo!, only a placenta

41
Q

what is the consequence of mosaicism on phenotype?

A

Variable. possibly less lethality!

42
Q

Females are mosaic?

A

X inactivations

43
Q

13, 14, 15, 21 and 22 are known as what?

A

Acrocentric chromosomes

44
Q

P arms do or do not contain coding DNA?

A

Do not!

45
Q

Robertsonian translocation involves what?

A

Fusions of two Qarms no P arms have 45 chromosomes

46
Q

Inversion of chromosomes involves what?

A

Two breaks in chromosomes rotation etc

47
Q

2 breaks in one arms is knows as what?

A

Paracentric inversion

48
Q

2 breaks in different arms is what?

A

Pericentric! inversion

49
Q

unbalanced rearrangements are usually inherited?

A

No sporadic!

50
Q

Unbalance rearrangement more likely in which sex?

A

Males

51
Q

What types of deletion can occur?

A

Interstitial or terminal

GIM (10 decks)

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