2. Chromosomes (1) Flashcards

Question

What is the probing process of FISH? (2)

Answer 1

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

Answer 2

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

Answer 3

▣ 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

Answer 4

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

Answer 5

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

Answer 6

Haploid (23 chromosomes)

Answer 7

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

Answer 8

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

Answer 9

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

Answer 10

▣ 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

Answer 11

Abnormalities

Answer 12

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

Answer 13

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

Answer 14

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

Answer 15

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

Answer 16

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

Answer 17

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

Answer 18

□ Missing □ Extra □ Switched – in a different place

Answer 19

▣ 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

Answer 20

Test: FISH, Array, MLPA or karyotype

Answer 21

▣ 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

Answer 22

Test: FISH, Array, MLPA or karyotype

Answer 23

▣ 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

Answer 24

Array if unbalanced or karyotype if balanced

Answer 25

▣ 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’

Answer 26

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

Answer 27

▣ 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

Answer 28

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

Answer 29

FISH, Array, MLPA or karyotype

2. Chromosomes (1) Flashcards

(78 cards)