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medical science xy1110 > genetics 7 > Flashcards

genetics 7 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

what is chromosome abnormalities the leading cause of

A
  • pregnancy loss
  • intellectual disabilities
    -1:150 live births
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2
Q

what are the centromere positions

A
  • metacentric - near the middle
  • Acrocentric - near the tip
  • submetacentric - between the middle and the tip
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3
Q

what is the karyotype

A

46XY or 46XX

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4
Q

how are chromosomes ordered

A
  • size - largest first
  • centromere position
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5
Q

what are the tips of chromosomes called

A

telomere

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6
Q

in metacentric what are the two arms called

A
  • short arm = p
  • long arm - q
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7
Q

what human chromosomes are acrocentric

A

13,14,15,21,22 and Y

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8
Q

what occurs with short arm in chromosomes

A
  • fewer genes
  • no essential genetic material
  • nucleolus organising regions (NOR) - rDNA
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9
Q

what is important about Q/G bands

A
  • A-T rich regions
  • giemsa banding
  • quinacrine-bright
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10
Q

what is important about R bands

A
  • G-C rich
  • hot phosphate buffer
  • giemsa stain
  • called a negative stain
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11
Q

what are the types of cytogenetic locations

A

chromosome –> arm–> region –> band –> sub-band
eg. 7q31.2

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12
Q

what does ploidy mean

A
  • number of sets of chromosomes in a genome
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13
Q

what does the DNA content mean

A
  • amount of DNA in a cell
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14
Q

what is a numerical abnormality

A
  • abnormal number of chromosomes
  • polyploidy - total chromsome copies
  • aneuploidy - individual chromosomal copies
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15
Q

what are the types of polyploidy

A
  • triploidy
  • tetraploidy
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16
Q

what are the types of aneuploidy

A
  • monosomy
  • trisomy
  • tetrasomy
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17
Q

what are structural abnormalities

A
  • deletions, insertions, inversions
  • translocations - reciprocal, robertsonian
  • rings
  • isochromosomes
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18
Q

what is triploidy

A
  • 69 chromsomes
  • caused by two sperm
  • very high morbidity - 1:10,000 live births
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19
Q

what is tetraploidy

A
  • 92 chromosomes
  • caused by mitotic failure in early embryo
  • few live births , very high morbidity
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20
Q

what is monosomy and what is an example

A
  • only one copy of a chromosome
  • very high morality
  • turner syndrome (X)
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21
Q

what is trisomy and what is an example

A
  • 3 copies of a chromosome
  • less severe
  • down-syndrome (cH21)
22
Q

what is tetrasomy and what is an example

A
  • four copies of a chromosome
  • cat eye syndrome (Ch22)
23
Q

what is turner syndrome and what are the symptoms and treatment

A
  • monosomy of X chromosome
  • short statue, normal intelligence, not mature during puberty, most infertile
  • hormone therapy
24
Q

what is klinefelter syndrome and what is the symptoms

A
  • trisomy of sex chromosome
  • taller than average, small testes giving slight feminine physique, infertile, learning disabilities, flat feet, curved little finger
25
Q

what is Down syndrome and what are the symptoms

A
  • trisomy of Ch21 - nondisjunction of egg cells
  • intellectual disabilities, characteristic facial appearance, weak muscle tone, 50% heart defects
26
Q

what is patau syndrome and what are the symptoms

A
  • trisomy of Ch13
  • 88% die in first year
  • orofacial clefts, malformed eyes, wide nose, severe developmental issues
27
Q

what is Edwards syndrome and what are the symptoms

A
  • trisomy of Ch18
  • slow growth before birth, small head, abnormally shaped jaw and mouth, overlapping fingers, heart defects
  • many die before one month, 5-10% live past 1 year
28
Q

what is nondisjunction

A
  • unequal distribution of chromosome pair in cell division
  • occurs in meiosis 1 and meiosis 2
29
Q

what are the causes of structure abnormalities

A
  • same number of chromosomes
  • unequal crossing over during meiosis
  • chromosomal breakage
30
Q

what are the types of structural abnormalities

A
  • balanced - no change in the amount of genetic material
  • unbalanced - gain or loss of chromosomal material - serious consequences
31
Q

what are the causes of DNA double strand breaks

A
  • Reactive oxygen species
  • Ionizing radiation
  • Chemotherapeutic drugs (Clastogens)
  • Meiosis
  • Lymphocyte development
  • Mobile genetic elements (viral)
32
Q

what is reciprocal translocation

A
  • between different chromosomes
  • removal or addition of DNA - genetic duplication/ deletion
33
Q

what is robertsonian translocation

A
  • acrocentric chromsomes - centromere near the tip
34
Q

what is the sex determining gene and where is it found

A

SRY gene
PAR1 - x and y chromosomes

35
Q

how does the SRY gene create gender

A

gene crossover creating XX males and XY females

36
Q

what is critical-du-chat syndrome and what are the symptoms

A
  • deletion - single break terminal deletion
  • characteristic cry, intellectual disability, small head
37
Q

what is wolf-hirshhorn syndrome and what are the symptoms

A
  • single break terminal deletion
  • facial characteristics, cleft palate, delayed growth and development, intellectual disability and seizures
38
Q

what is microdeletions

A
  • <5 million bases
  • need high resolution banding
  • FISH and aCHG techniques
39
Q

what is Prader-will syndrome and what are the symptoms

A
  • 70% micro deletions of 15q11
  • 50% of patients 15q11-q13
  • due to imprinting
  • Paternal microdeletion ch15 → Prader–Willi syndrome
    Intellectual disability, short stature, obesity, hypotonia, characteristic facies, small feet
40
Q

what is angel man syndrome

A

Maternally microdeletion ch15 → Angelman syndrome
Intellectual disability, ataxia (co-ordination, balance and speech), uncontrolled laughter, seizures

41
Q

what are the causes of insertions

A
  • offspring of person with reciprocal translocations
  • unequal crossover during meiosis
42
Q

what is an example of insertion

A
  • x-linked colour blindness
43
Q

what is charcot-marie-tooth disease and what are the symptoms

A
  • progressive damage to peripheral nerves
  • high arches, flat feet or curled toes
44
Q

what are the causes of inversions

A
  • reinsertion of double break
  • wrong orientation
  • balanced
45
Q

what is pericentric inversions

A
  • centromere inverted
46
Q

what are paracentric inversions

A
  • no centromere involved
47
Q

what is an example of inversions

A
  • servere hemophillia A
  • interruption of factor VII gene
48
Q

what causes ring chromosomes

A
  • breakage at both tips —> ends fuse
  • usually de novo
  • rarely inherited
  • most common Ch 14 and 22
49
Q

what is an example of ring chromosomes

A

Female ring X chromosome 46,X,r(X)

50
Q

what are isochromosomes

A
  • chromosomes divided along wrong axis
  • chromosomes with two p or q arms or robertsonian translocation of Ch21q
51
Q

what are the 3 types of Edward syndrome and what are the symptoms

A

Full Edwards’ syndrome - Trisomy Ch18
- Severe, high mortality before birth

Mosaic Edwards’ syndrome - Extra Ch18 in some cells
- Milder effects
- May live to 1 year or adulthood

Partial Edwards’ syndrome – Extra sections of Ch 18

52
Q
A

medical science xy1110 (40 decks)

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