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MFoM > 05b: Chromosomes > Flashcards

05b: Chromosomes Flashcards

1
Q

The short arm of the chromosome is called:

A

The P arm

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2
Q

The long arm of the chromosome is called:

A

The q arm

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3
Q

Location of centromere in meta centric chromosome

A

Middle

Chromosome has nearly equal P and q arms.

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4
Q

Location of centromere in submetacentric chromosome

A

Closer to one side, so P arms shorter than q arms

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5
Q

Location of centromere in acrocentric chromosome

A

Very close to one end of chromosome (almost no p arm)

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6
Q

The less condensed the chromosomes are, the (less/more) bands appear.

A

More

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7
Q

A(n) (X) stain is used to image chromosomal banding patterns.

A

X = giemsa

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8
Q

Dark chromosomal bands are gene (rich/poor) and has which type of chromatin?

A

Poor; heterochromatin

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9
Q

Light chromosomal bands are gene (rich/poor) and has which type of chromatin?

A

Rich (50+ genes per band); euchromatin

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10
Q

(Heterochromatin/euchromatin) is lightly packed and actively transcribed.

A

Euchromatin

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11
Q

Chromosomes can be profiled based on:

A
  1. Size
  2. Centromere position
  3. Banding pattern
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12
Q

What are the tissue sources used to profile chromosomes?

A
  1. Blood (somatic cells)
  2. Cheek swab (somatic cells)
  3. Amniocentesis/CVS (prenatal screen)
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13
Q

A normal male karyotype would have what nomenclature?

A

46, XY

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14
Q

Multiple fertilization could result in (X)ploidy. Give potential nomenclature for this individual.

A

X = tetra- (4n)

96, XXXX

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15
Q

Presence of an abnormal number of chromosomes, but does not include a difference of one or more complete sets of chromosomes (just certain genes).

A

Aneuploidy

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16
Q

Nondisjunction usually associated with (sperm/oocytes/both equally).

A

Oocytes

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17
Q

At what maternal age does incidence of trisomy start to skyrocket?

A

34-35

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18
Q

Why would mitotic post-zygotic nondisjunction be (more/less/equally) severe as meiotic nondisjunction?

A

Less severe! Cell with just one chromosome usually won’t contribute

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19
Q

A male with trisomy 18 would have what nomenclature?

A

47, XY, +18

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20
Q

In DNA microarray, what’s being compared/assessed?

A

Compare quantity of DNA between normal control sample and fetal sample

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21
Q

What do the colors in DNA microarray indicate?

A

Yellow: equal amount DNA
Red: extra amount DNA
Green: missing amount DNA

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22
Q

In DNA microarray, is the sample or probe or neither fixed?

A

Probes fixed, wash sample over them

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23
Q

Nuclear genome accounts for over (X)% of human genome.

A

X = 99

24
Q

Mitochondrial genome allows the organelle to synthesize its own (X), that function in:

A

X = proteins

Cell respiration (ETC)

25
Q

Why are (nuclear/mitochondrial) genes especially susceptible to mutation?

A

Mitochondrial;

Respiration and oxidative phosphorylation produce substantial amounts of reactive oxygen species (ROS), which damage DNA

26
Q

What’s mitonuclear match?

A

Nuclear genes match rates of mutation/evolution of mitochondrial genes in order for the proteins to co-evolve and keep machinery in sync

27
Q

Define heteroplasmy.

A

Tissues, within same individual, vary with the amount of mutant mitochondria since the segregation isn’t regulates

28
Q

Why are mitochondria inherited through (paternal/maternal) descent only?

A

Maternal;

Inherited with the cytoplasm (eggs contain 100,000 and sperm only 100)

29
Q

T/F: a cell with a few mutant mitochondria may have normal phenotype.

A

True - must pass threshold for phenotypic expression

30
Q

Analysis that detects small deletions and duplications (less than 0.5 million bp).

A

Chromosomal microarray

31
Q

Analysis that detects deletions and duplications greater than 7-10 million bp.

A

Karyotype

32
Q

Which analysis can detect both copy number variation and positioning?

A

Karyotype (NOT microarray)

33
Q

Edwards syndrom, aka (X), has which key symptoms?

A

X = trisomy 18

Clenched fist (2nd finger overlaps 3rd), low-set ears, mental retardation, cardiac malformations

34
Q

Trisomy 13 is also called:

A

Patau syndrome

35
Q

Trisomy 21 is also called (X). A male patient would have the nomenclature:

A

X = Down syndrome

47, XY, +21

36
Q

What’s a chromosomal translocation?

A

Chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes

37
Q

Example of female with Robertsonian translocation nomenclature:

A

46, XX, t(14; 21), +21

38
Q

An individual with chromosomal translocation (i.e. Robertsonian) has how many chromosomes?

A

46

39
Q

T/F: You can be an asymptomatic carrier of Robertsonian translocation.

A

True

40
Q

T/F: Aneuploidy is only really found in autosomal chromosomes.

A

False - in sex chromosomes also

41
Q

How do mammals carry out dosage compensation for sex chromosomes?

A

X-inactivation

42
Q

Genes subject to escaping X-inactivation are found on (p/q/both) arm(s).

A

Primarily on P-arm

43
Q

T/F: Genes that escape X-inactivation are expressed in two copies for males as well as females.

A

False - only in females

44
Q

The only viable monosomy, (X), has the nomenclature:

A

X = Turner syndrome

45, XO

OR… 46, XX, i(Xq)

45
Q

Give example of a syndrome that results, despite X-inactivation.

A

Klinefelter’s syndrome

46
Q

List the two types of chromosomal inversions.

A
  1. Paracentric (not involving centromere)

2. Pericentric (involving centromere)

47
Q

Consequence of paracentric inversion in offspring.

A

Unbalanced offspring AND genomic instability (one chromosome has no centromere, the other has two)

48
Q

Consequence of pericentric inversion in offspring.

A

Unbalanced offspring

49
Q

What’s one assay that’s especially useful to look for translocations?

A

Spectral Karyotyping (SKY) with 24 different color labels for each chromosome

50
Q

A Philadelphia chromosome is the result of (balanced/unbalanced) (X). What disease associated?

A

Balanced;
X = reciprocal translocation

Chronic myelogenous leukemia

51
Q

What defines a balanced translocation?

A

Cells still diploid (no extra/missing chromosomal material)

52
Q

(X) fusion protein, a result of a (Y) translocation, is problematic in that it:

A 
X = bcr-abl
Y = reciprocal

Acts as kinase in wrong time/place

53
Q

T/F: Vast majority of reciprocal translocations create Philadelphia chromosome.

A

False

54
Q

Principles of X-inactivation:

A
  1. Random choice of Xi

2. If one X is defective, choice no longer random

55
Q

If an X chromosome is defective, how is priority set for the Xi chosen?

A
  1. Preserve activity of one entire X chromosome equivalent

2. Preserve autosomal sequences, if possible

56
Q

What defines an isochromosome?

A

Structural abnormality in which the chromosome are mirror images of each other

57
Q

5p15 chromosomal deletion:

A

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MFoM (20 decks)

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