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MBBCh 2- HAEM2000A > 2. Chromosomes (1) > Flashcards

2. Chromosomes (1) Flashcards

1
Q

DNA is packaged into a structure called the _______. The chromosomes are found within the nucleus of the cell.

A

chromosome

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2
Q

Homologous chromosomes:

A

Set of one maternal and one paternal chromosome that pair up with each other inside a cell during cell division.

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3
Q

Sister chromatids:

A

Refers to the identical copies (chromatids) formed by the DNA replication of a chromosome, with both copies joined by a common centromere.

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4
Q

Centromere:

A

Essential to the division of cells and ensure
the accurate segregation of chromosomes.

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5
Q

Telomeres:

A

A region of repetitive nucleotide sequences
at each end of a chromosome, which protects the end
of the chromosome from deterioration or from fusion
with neighbouring chromosomes.

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6
Q

Types of chromosomes
▣ Chromosomes are classified according to the position of the centromere: (4)

A
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7
Q

Visualization of the type of chromosomes:

A
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8
Q

What are the types of Cytogenetic tests? (5)

A
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9
Q

What is cytogenic test resolution?

A
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10
Q

What is the Karyotype? (4)

A

▣ A karyotype is an individual’s collection of
chromosomes
▣ It is the number and appearance of chromosomes in
the nucleus of a eukaryotic cell
▣ The term also refers to a laboratory technique that
produces an image of an individual’s chromosomes
▣ Involves the isolation, staining and visual examination
of chromosomes

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11
Q

What is the cell cycle?

A
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12
Q

Karyotype technique: (3)

A
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13
Q

How are karyotypes cultured? (3)

A
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14
Q

How are karyotypes harvested? (3)

A
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15
Q

How are karyotypes analysed? (3)

A
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16
Q

What are the types of staining? (3)

A
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17
Q

Metaphase spread vs Karyogram:

A
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18
Q

Karyotype resolution
▣ Total # of bands ______
▣ Depends on how _______ chromosomes
are- metaphase or prophase
▣ Generally 350-____

A

visible
condensed
550

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19
Q

What is the ISCN?

A

International Standard for Cytogenic Nomenclature

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20
Q

ISCN Abbreviations:

A
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21
Q

What is Fluorescent In-Situ Hybridization (FISH)? (2)

A

▣ Detects small deletions/duplications which are not
visible using conventional cytogenetic techniques
▣ Molecular cytogenetic method used to detect and
localize the presence or absence of specific DNA
sequences on chromosomes

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22
Q

FISH
▣ Need to know what you are looking for
▣ Utilizes ________ base pairing
▣ _______ bind to region of interest

A

complimentary
probes

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23
Q

FISH technique: (4)

A
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24
Q

What is the denaturing process of FISH? (3)

A

▣ To generate single stranded DNA
▣ Formamide and ethanol
▣ Heat- water bath or hotplate

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25
Q

What is the probing process of FISH? (2)

A

▣ Specifically designed short section of single-
stranded DNA
▣ Fluorescently labelled to enable visualisation
when bound

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26
Q

What is the hybridising process of FISH? (2)

A

▣ Binding (re-annealing) of probe and sample
single-stranded DNA
▣ Heat and humidity

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27
Q

What is the analysing process of FISH? (5)

A

▣ Visualise using fluorescent microscope
▣ Each hybridised probe is visualised as a
distinct signal
▣ Control- different colour fluorescence
▣ Analyse multiple cells
▣ Deletion <2 signals; duplication >2 signals

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28
Q

What are the uses of FISH? (3)

A

▣ Microdeletions and duplications
▣ Confirm rearrangements
▣ ID origin of material (ring chromosome/
satellite chromosome)

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29
Q

How are microdeletions visualised?

A
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30
Q

22q11 microdeletion:

A
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31
Q

1p36 duplication:

A
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32
Q

Translocation:

A
33
Q

Marker chromosome:

A
34
Q

Karyotype vs FISH: (7)

A
35
Q

Normal somatic cell:

A

Diploid (46 chromosomes). Contains 2 haploid
chromosome sets.

36
Q

Normal gamete:

A

Haploid (23 chromosomes)

37
Q

Types of numerical abnormalities
Polyploidy: (2)

A

▣ More than 2 haploid chromosome sets
▣ Example: triploidy (3 haploid chromosome
sets = 69 chromosomes)

38
Q

Types of numerical abnormalities
Aneuploidy: (3)

A

▣ Gain or loss of one (or more) chromosomes
▣ Example: trisomy (46 + 1 = 47 chromosomes)
▣ Example: monosomy (46 – 1 = 45 chromosomes)

39
Q

▣ Normal female: 46, XX
▣ Normal male: 46, XY
▣ Triploidy female: 69, XXX
▣ Triploidy male:
▣ Trisomy:
▣ Monosomy:
▣ Mosaic:

A

▣ Triploidy male: 69, XXY or
69, XYY
▣ Trisomy: 47, XY, +21
▣ Monosomy: 45, XX, -21
▣ Mosaic: 46, XX/47, XX, +21

40
Q

What does Non-disjunction during meiosis result in? (2)

A

▣ Non-disjunction in meiosis I
□ Two homologous chromosomes fail to
separate
□ Results in trisomic or nullisomic embryos
▣ Non-disjunction in meiosis II
□ Two sister chromatids don’t separate
□ Results in trisomic or nullisomic embryos

41
Q

Mechanisms resulting in polyploidy
▣ Caused by fertilisation _________.

A

Abnormalities

42
Q

▣ Digyny:

A

□ Diploid ovum (as a result of non-expulsion of the
second polar body, for example) is fertilised by a
haploid spermatozoa

43
Q

▣ Diandry: (2)

A

□ Fertilisation of one oocyte by two spermatozoa
□ Four times more frequent than digyny

44
Q

Abnormal fertilisation resulting in polyploidy:

A
45
Q

What is Mosaicism? (2)

A

□ Occurs when there are two or more different cell
lines present
□ The different cell lines have different karyotypes
(chromosome arrangements)

46
Q

What is Chimerism? (2)

A

□ Two or more cell lines present originating from two
or more zygotes
□ May arise from early fusion

47
Q

What is Trisomy 21 (Down syndrome)? (3)

A
48
Q

Clinical features of Down syndrome: (8)

A

▣ Characteristic dysmorphic features
▣ Intellectual delay
▣ Global developmental delay
▣ Hypotonia
▣ Congenital heart defects
▣ Hearing loss
▣ Vision problems, cataracts
▣ Hypothyroidism

49
Q

What is Trisomy 13 (prev. Patau syndrome)?

A
50
Q

What is Trisomy 13 (prev. Patau syndrome)?

A
51
Q

What is Turner syndrome?

A
52
Q

What is Klinefelter’s syndrome?

A
53
Q

▣ A chromosome imbalance due to structural changes
within the chromosome, such as: (7)

A

□ Deletions
□ Duplications
□ Translocations
□ Inversions
□ Insertions
□ Ring chromosomes
□ Isochromosomes

54
Q

▣ One chromosome can have multiple structural
abnormalities
▣ Usually, the total number of chromosomes is normal
▣ There is a change in their structure: (3)

A

□ Missing
□ Extra
□ Switched – in a different place

55
Q

What is a deletion? (3)

A

▣ Part of the chromosome is missing or deleted
□ Terminal or interstitial deletion
▣ Some genetic material is missing
□ Can cause syndromic features
□ Depends on the genes involved in deletion
▣ Sporadic or dominant
□ If dominant: 50% recurrence risk

56
Q

How can you test for a deletion? (4)

A

Test: FISH, Array, MLPA or karyotype

57
Q

What are Interstitial and terminal deletions?

A
58
Q

What are some syndromes associated with deletions? (3)

A
59
Q

What is a duplication? (3)

A

▣ Part of the chromosome is duplicated
□ Terminal or interstitial duplication
□ Direct (tandem) or inverted
▣ Results in extra genetic material
□ Severity depends on the genes involved
□ Less severe than deletions
▣ Sporadic or inherited
□ If inherited: 50% recurrence risk

60
Q

How can you test for duplications? (4)

A

Test: FISH, Array, MLPA or karyotype

61
Q

What are interstitial and terminal duplications?

A
62
Q

What are the syndromes associated with duplications?

A
63
Q

What is a translocation: Reciprocal? (3)

A

▣ Exchange of material between chromosomes
▣ Balanced:
□ No loss or gain of genetic material
□ Individuals are usually phenotypically normal
▣ Unbalanced:
□ Gain or loss of genetic material – severity depends on size
□ Can be inherited from a balanced parent – recurrence is complicated

64
Q

How do you test for a reciprocal translocation?

A

Array if unbalanced or karyotype if balanced

65
Q

What is a Translocation: Robertsonian? (2)

A
66
Q

How do you test for a robertsonian translocation?

A

Karyotype

67
Q

Robertsonian vs reciprocal translocation:

A
68
Q

What are Recurrent miscarriages?

A
69
Q

What is an inversion? (3)

A

▣ Portion of a chromosome broke off, inverted and
reattached
▣ Pericentric or paracentric
▣ If isolated the individual is often phenotypically normal
□ Can be a ‘normal variant’

70
Q

How do you test for an inversion?

A

Karyotype

71
Q

What are the types of inversions? (2)

A
72
Q

What is an Insertion? (3)

A

▣ Portion of a chromosome broke off and is inserted
elsewhere
▣ Interchromosomal or intrachromosomal
▣ Direct insertion or inverted insertion

73
Q

How do you test for an insertion?

A

Karyotype

74
Q

What is a ring chromosome? (5)

A

▣ Portion of a chromosome broke off and formed a ring
▣ Can happen with or without loss of genetic material
▣ Very rare
▣ Often severe
▣ Usually sporadic

75
Q

How do you test for ring chromosomes?

A

Karyotype

76
Q

What is an isochromosome? (2)

A

▣ Formed by a mirror image copy of a chromosome
segment
▣ Results in a gain and loss of genetic material

77
Q

How do you test for isochromosomes? (4)

A

FISH, Array, MLPA or karyotype

78
Q

What are some syndromes associated with isochromosomes?

A

MBBCh 2- HAEM2000A (30 decks)

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