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Flashcards in cytogentic basis of inheritance Deck (93):
1

define cytogenetics

study of chromosomes within a cell.

2

what is conventional cytogenetic analysis

metaphase chromosome analysis (chromosomes are condensed and can be visible)
G banding

3

what is molecular cytogenetics

cytogenetics analysis at the molecular resolution at all stages of the cell cycle- DNA in situ.

4

examples of molecular cytogenetics

• FISH
• Microarray CGH
• Next generation sequencing (NGS)
• MLPA
• QF-PCR
• qPCR

5

How long does the cell cycle take

24hrs

6

what are the different stages in the cell cycle

growth phase 1
synthesis
growth phase 2
mitosis
cytogenetics

7

how long is growth phase 1 of the cell cycle and what happens during this phase

6-12 hrs
cellular components are duplicated excluding chromosomes.

8

how long is the synthesis phase of the cell cycle and what happens during this phase

6-8 hrs
each of the 46 chromosomes is duplicated by the cells.

9

how long is growth phase 2 of the cell cycle and what happens during this phase

3-4 hrs
the cell double checks the duplicated chromosomes for errors and make needed repairs.

10

how long is mitosis

1 hr.

11

What are the stages of mitosis

Interphase, prophase, metaphase, anaphase, telophase and cyokinetics.

12

what happens in each stage of mitosis
IMPACT

• Interphase- all chromosomes loose
• Prophase- chromosome condense
• Metaphase- chromosome (made of 2 chromatids)- line up along the midline.
• Anaphase- the sister chromatids are separated
• Telophase- the cell begins to split into 2
• Cytokinesis- cell splits in 2 cells and chromosomes unwrap again.

13

In what stage of the cell cycle does G banding take place

metaphase.

14

How are chromosomes laid out on the template slide for G-banding.

line up chromosomes 1- 23, paired up and in order.

15

what are the main 2 types of cytogenetic abnormalities.

numerical
structural

16

what is the dosage effect
(type of cytogenetic abnormality)

gain or loss in chromosome number
(loss is worse)

17

How can a gene be disrupted

breakpoint, inappropriate activation/ inactivation.

18

define genomic imprinting

alleles from 1 parent are suspended.

19

what is the position effect on a gene

A gene in a new chromosomal environment functions inappropriately

20

what has a more severe phenotype sex chromosome imbalance or autosomal imbalance.

autosomal imbalance.

21

define anueploidy

gain (trisomy) or loss (monosomy) of chromosomes

22

define polyploidy

gain whole sets (triploidy or tetraploidy)

23

define mosacism

diploidy and anueploidy is one human genome.

24

where do numerical abnormalities arise ( in which stage of cell development)

gametogenesis (meiosis- most errors in female meiosis)
fertilisation
early cleavage (post zygotic non disjunction).

25

what factors increase the risk of numerical abnormalities in chromosomes during gametogenesis.

maternal age >35

26

what are the stages in meiosis.

prophase 1- DNA replicate
Metaphase 1- chiasmta visible
Anaphase 1- chromosome separation
Telophase- cells begin to separate
Cytokinesis- secondary gametocyte.
Meiosis 2 - sister chromatics are pulled apart.

27

what is the most common meiotic error

non disjunction

28

when does chromosome disjunction occur in meiosis and what does it form

meiosis 1
2 disomic gametes ( which have twice the content of normal gametes)
2 nullisomic gametes ( no content)

29

when does chromatid disjunction occur in meiosis and what does it form

meiosis 2
1 disomic 1 nullisomic and 2 normal gametes.

30

most common 3 autosomal anueplodiues

Trisomy 21, trisomy 18 and trisomy 13.

31

what are the head abnormalities seen in a patient with trisomy 21

Eyes: upward slanting; brushfield spots (on iris)
Nose: Small
Ears: abnormally shaped/low set
Tongue: protruding
General – flat face, brachycephalic, short neck .

32

what percentage of children with trisomy 21 spontaneously abort

75%

33

what are the neurological abnormalities seen in a patient with trisomy 21.

Learning disabilities (mild to moderate IQ 30-60)

34

what are the hands and feet abnormalities seen in a patient with trisomy 21.

single palmar crease
short broad hands
5 th finger clinodactyly- small finger.
wide sandal gap.

35

what fertility problems do males and females with trisomy 21 face

females none.
males infertile.

36

what other conditions are individuals with trisomy 21 more prevalent to.

alzheimer's
hypothroid
obesity/ coeliac, arthritis, diabetes, hearing loss seizures.

37

what percentage of trimsomy 18 spontaneously abort

95%

38

what head abnormalities seen in a patient with trisomy 18.

microcephaly, low set ears, micrognathia (small jaw), cleft lip and palate

39

what are the hands and feet abnormalities seen in a patient with trisomy 18.

clenched hands (seen on scan)
polydactyly
overlapping fingers (rocker bottom feet).

40

what mental abnormalities seen in a patient with trisomy 18.

mental retartdation.

41

what organ malformation occurs in trisomy 18

umbilical and inguinal hernia
congenital heart disease
congenital kidney abnormality
eye abnormality (cataracts and micropthalmia)

42

what percentage of trisomy 13 spontaneously abort

95%

43

what are mental abnormalities seen in a patient with trisomy 13.

Mental retardation severe
Microcephaly/ sloping forehead
Defects of brain – holoprosencephaly

44

What are the hand and feet abnormalities of trisomy 13

Polydactyly & fingers flexed

45

what are the head abnormalities of trisomy 13

Eyes – microphthalmia, coloboma, retinal dysplasia, palpebral fissures slanted
Cleft lip and/or palate
Ears abnormal and low
Can have Cyclops

46

what other abnormalities of trisomy 13 are evident

Heart defect
Abnormal genitalia

47

what types of structures of the human body does trisomy 13 present with

midline structures are affected

48

How long do female eggs stay in meiosis 1

foetus 5 months until puberty

49

when do eggs go into meiosis 2

once they have been fertilised or bleed out in puberty.

50

what is age dependent deterioration of meiotic structures

long the eggs stay in meiosis 1 more likely the environment will impact them) - hormonal imbalance, irradiation, oral contraceptives, alcohol

51

Are sex chromosome anueploidies age dependent

no

52

Are autosomal anuplodies age dependent

Yes- maternal age.

53

give 2 examples of conditions which are sex chromosome anueplodiy

Turners (45 X)
Klinefelter. (47XXY)

54

What reproductive problems are faced with turners syndrome

Loss of ovarian function
No puberty
Infertility

55

what lymphatic problems do people with turners syndrome face

Webbed neck
Swelling of hands &/or feet

56

what other abnormalities do people with turners have

Skeletal Abnormalities – short stature
Coarctation of aorta
IQ generally normal/reduced compared to sibs

57

how is klinefelters diagnosed

infertility or hypogonadism.

58

what fertility problems do patients with klinfelters face.

lack secondary sexual characteristics
Testicular dysgenesis (abnormal development.
gynaecomastia

59

what growth problems do people with linfelters face

Normal in infants, then accelerates
Adults long legs and arms

60

What are the 2 main errors in fertilisation

1.Polyploidy (usually triploidy)
2.Molar pregnancy (double paternal, no maternal)- no genetic content.

61

what percentage of triploides spontaneously abort

99.9%

62

define digmy

twice the genetic content in egg

63

define diplospermy

twice the genetic content in the sperm.

64

define dispermy

2 sperm fertilise 1 egg

65

what is the consequence of double maternal content

small placenta
Macrocephaly - all available nutrients fo to the brain to ensure survival.
significant grwoth delay.

66

what is the consequence of double paternal content

massive placenta
some growth delay

67

what does the maternal genome code for foetus or placenta

foetus

68

what does the paternal genome code for foetus or placenta

placenta

69

consequences of a molar pregnancy

Double paternal genome
Massive cystic placenta

70

define molar pregnancy

haploid sperm and empty egg results in haploid zygote

71

when does monocaism happen

post zygotically.

72

2 main types of chromosome rearrangements

Translocation
Inversion

73

2 types of translocations

reciprocal
robertsonian

74

2 types of inversions

pericentric
paracentric

75

what is reciprocal translocation

• Break and exchange
• Content is the same just rearranged

76

each type you break a chromosome what is the % chance that you will break a gene

3%

77

what is a robertsonian translocation

whole arm fusion

78

what chromosome undergo robertsonian translocation

acrocentrics-13,14,15,21,22

79

does the long q arm of short p arm contain DNA information

long q arm.

80

is there reproductive risk in robertsonin and reciprocal translocation

Yes

81

define pericentric inversion

breaks either side of centromeres

82

what is paracentric inversion

breaks on one side of the chromosome.

83

do inversion have a reproductive risk

Yes

84

In robertsonian tranlocations is the phenotype of the patient affected

No, all genetic material is still present
q ars fuse and p are lost (but p has no genetic information)

85

unbalanced rearrgaments can be caused by

CNV- copy number variation
Deletions and duplications

86

2 types of deletions

Interstitial
terminal

87

what is a interstitial deletion

segment lost from within the chromosome.

88

what is a terminal deletion

segment lost from the end of the chromosome.

89

what is worse a chromosome loss of duplication

loss

90

what causes the phenotype in deletions and duplications

abnormal gene dosage.

91

what causes deletions and duplications to occur

• Mediated by low copy repeats or duplications.
• Defined regions of repetitive DNA
• So when chromosome line up the similar regions can mismatch and pair together.
• Chaismata occurs leading to deletion and duplication.

92

what causes variable clinical expression of deletions and duplications

variable size of imbalance, other genetic and environmental effects

93

what is a ring chromosome

terminal ends of a chromosome are detached and then it forms a ring structure (one end attaches to the other)