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Genetics > lecture 4 > Flashcards

lecture 4 Flashcards

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1
Q

when examining a karotype which blood cells do we usually look at

A

we look at the white blood cells because red blood cells do not have nuclei

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2
Q

centromere

A

a constriction in the chromosome involved in chromosome replication

(region of a chromosome that serves as a point of attachment for spindle fibers during cell division)

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3
Q

which arm is long and which is short

A

p = short arm
q = long arm

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4
Q

metacentric chromosome

A

type of chromosome where the centromere is located near the middle, dividing the chromosome into two arms of approximately equal length.

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5
Q

acrocentric chromosome

A

where the centromere is located near one end, resulting in one long arm and one short arm

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6
Q

in humans which chromosomes are acrocentric

A

13, 14, 15, 21 and 22

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7
Q

what order is information listed in the standard method when talking about chromosomes

A
  • which chromosome
  • which arm
  • which band
  • which sub-band
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8
Q

what does it mean by the ABO gene is on chromosome 9q34

A

the ABO blood gene is on the 4th sub band of the 3rd band on the long arm of chromosome 9

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9
Q

what is the standard description for a karotype

A

1) number of chromosomes
2) sex chromosomes
3) numerical abnormalities
4) structural abnormalities

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10
Q

what do you write for the sex chromosomes of men

A

XY

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11
Q

what do you write for the sex chromosomes of women

A

XX

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12
Q

list 5 different numerical chromosomal abnormalities

A

trisomy
tetrasomy
double trisomy
monosomy
polyploidy

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13
Q

Trisomy

A

three copies of a chromosome instead of 2

can occur in any chromosome but most common is trisomy 21 (down syndrome)

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14
Q

tetrasomy

A

four copies of a particular chromosome instead of 2

most common case is tetrasomy X, which involves four copies of the X chromosome in females

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15
Q

double trisomy (48,XXX, +21)

A

double trisomy refers to having an extra copy of two different chromosomes

in this case they have an extra X chromosome and an extra chromosome 21

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16
Q

monosomy

A

they have 45 chromosomes instead of 46

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17
Q

polyploidy

A

condition where the organism has more then 2 sets of chromosomes

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18
Q

triploidy

A

a cell that has an extra set of chromosomes

(69 chromosomes, three sets all together)

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19
Q

tetraploidy

A

extra 2 sets of chromosomes

(has 4 sets all together, 92)
more common to appear in leukemia cells

20
Q

5 common chromosome abnormalities

A

down syndrome
patau syndrome
edward syndrome
turner syndrome
klinefelter syndrome

21
Q

what is crucial when looking at structural abnormalities

A

has the person lost or gained any genetic material

22
Q

pericentric inversion

A

an inversion that has gone round the centromere

23
Q

paracentric inversion

A

chromosomal rearrangement that occurs within one arm of the chromosome (it does not involve the centromere)

people are usually fine

24
Q

isochromosome

A

has two long arms instead of a long arm and a short arm

25
Q

reciprocal translocation

A

exchange of genetic material where two arms have swapped over

26
Q

result of a reciprocal translocation

A

the person is usually fine because it is a balanced rearrangement and most of the breaks are liking to happen in a non coding region

27
Q

how common is down syndrome

A

1 in 700 births

28
Q

what are common clinical issues down syndrome people may have

A
  • developmental delays
  • intestinal atresias
  • epilepsy
  • hypothyroidism
  • deafness
  • leukemia
29
Q

nullisomic gamete

A

missing both copies of a particular chromosome pair.
lacks one entire chromosome pair out of the usual two sets of chromosomes.

30
Q

what happens is a nullisomic gamete is fertilized with a normal gamete

A

resulting zygote would have one copy of the chromosome pair

would not give rise to a baby, does not implant or is miscarried very early

31
Q

what is the chance of the child having down syndrome if the mother is carrying a chromosomal rearrangement

A

20-25%

32
Q

what is the chance of the child having down syndrome if the father is carrying a chromosomal rearrangement

A

3-5%

33
Q

Patau’s syndrome

A

also known as trisomy 13, extra chromosome 13

34
Q

neonatal death

A

death of a newborn within the first 28 days of life

35
Q

Patau syndrome results in

A
  • holoprosencephaly ( a single small forebrain)
  • cleft lip and palate
  • congenital heart disease
    Polydactyly: Extra fingers and/or toes

usually neonatal death or stillbirth

36
Q

Edward syndrome other name

A

trisomy 18 (extra copy of chromosome 18)

37
Q

affects of Edward’s syndrome

A
  • growth retardation
  • clenched hands
  • rocker bottom feet
  • congenital heart disease
  • exomphalos (intestinal contents outside abdomen)

usually neonatal or stillborn

38
Q

how common is Edward’s syndrome

A

1 in 3000 births

39
Q

meiotic non dysjunction

A

when homologous chromosomes fail to separate properly during meiosis, leading to an imbalance of chromosomes in the resulting gametes.
can occur during either the first or second meiotic division

40
Q

Turner’s syndrome

A

45, X
absence of one of the X chromosomes usually found in women

41
Q

turner’s syndrome clinical features

A
  • short stature
  • ovaries do not develop
  • webbed neck
  • swollen feet and hands (peripheral lymphoedema)
42
Q

Klinefelter syndrome

A

47, XXY
affects males, they have an extra X chromosome

43
Q

clinical features of Klinefelter syndrome

A
  • hypoganadism: underdeveloped testes
  • infertility
  • long limbs
  • learning difficulties
44
Q

risk of Klinfelter syndrome

A

1 in 1000 males

45
Q

indications for chromosomal analysis

A
  1. multiple congenital anomalies
  2. ambiguous genitalia
  3. primary amenorrhea
  4. primary male infertility
    5, recurrent miscarriages
  5. significant unexplained developmental delay
  6. prognostic features in leukemia
46
Q

Di George syndrome

A

also known as 22q11 deletion syndrome

1 in 4000 births

Genetics (22 decks)

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