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GT4300 Advanced Medical Genetics > Lecture 1 > Flashcards

Lecture 1 Flashcards

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1
Q

Ploidy Range

A

The number of sets in an organism while applying the formula: Ploidy level (Haploid Number) +/- 11

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2
Q

Haploid Range

A

23 +/- 11 = 12-34

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3
Q

Diploid Range

A

46 +/- 11 = 35-57

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4
Q

Triploid Range

A

69 +/- 11 = 58-80

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5
Q

Tetraploid Range

A

90 +/- 11 = 81-103

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6
Q

Composite Karyotype

A

All the collected abnormalities put together. Because if every sample cell has a different karyotype ( and no 2 cells share the same structural or numerical aberrations), it can be seen which abnormalities have actionable treatments.

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7
Q

Single Cell Evolution

A
  • It exists simultaneously with Clonal Evolution.
  • It states that just because one evolutional clone is be treated, not all clones are.
  • It is multiple pockets of clones, instead of a one cell line.
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8
Q

Clonal Evolution

A
  • Observed in cancer, it begins with a timestamp of a karyotype for chromosomal change.
  • Observing the parent cell will let us know if the mutation is outsmarting the treatment.
  • It parallels Darwinian Natural Selection.
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9
Q

Ring Chromosomes

A
  • Formed when 2 terminal breaks occur on the same chromosome, then the top and bottom become “sticky” and form a union.
  • There is a loss of genetic material.
  • Like dicentrics, are highly unstable because the break of lag anaphase.
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10
Q

Isochromosomes

A
  • Formed when there is a misdivision of a centromere.
  • Occasionally centromere divides horizontally.
  • Results in 1 daughter cell with 2 sister chromatids on each arm of a chromosome.
  • One arm is a mirror image of the other.
  • Trisomic for one arm / Monosomic for the other.
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11
Q

What is a good example of an isochromosome?

A

Turner Syndrome

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12
Q

Duplication

A
  • When a portion of the chromosome is duplicated.
  • Extra material results in functional trisomey.
  • Duplicated material can be in the same order, or inverted and reversed.
  • Can be direct or indirect.
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13
Q

Paracentric Inversion

A
  • When both breaks are in the same arm of a chromosome.
  • Centromeres are NOT involved.
  • Products are either acentric or dicentric.
  • Negligible outcome for an unbalanced offspring.
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14
Q

Pericentric Inversion

A
  • When there is a break on the short arm and the long arm of a chromosome.
  • Does not effect the phenotype of the carrier.
  • Each unbalanced product has a duplication, deficiency, or is nonviable.
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15
Q

Inversions

A
  • Results when 2 breaks occur on the same chromosome.
  • The middle segment rotates 180 degrees before DNA repair.
  • There is no net loss, only changes the gene order.
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16
Q

What are the two types of Inversions?

A

Pericentric - Breaks on both arms

Paracentric - Breaks on only one arm

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17
Q

Deletion

A
  • Results in a loss of genetic material.
  • Is the most common.
  • Functional monosomy.
  • Can be terminal or interstitial.
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18
Q

Insertions

A
  • Parts of a chromosome inserted into another chromosome.
  • Can be direct or inverted.
  • Can be Intra or Inter.
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19
Q

What are the 2 types of direct Insertions?

A

Intra - Insertion within the same chromosome

Inter - Insertion between 2 or more chromosomes

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20
Q

Telomeres

A
  • Prevent the chromosomes from forming a circle or rings.

- The shorter a telomere is the older the person is.

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21
Q

Dicentric Chromosomes

A
  • Posses 2 centromeres (and 4 arms) from 2 chromosomes.
  • Unless one of the centromeres is inactivated, an abnormality in mitosis, an anaphase bridge, or lagging chromosomes can occur.
  • There is a loss of acentric fragments.
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22
Q

Anaphase Bridge

A

Occurs when each different centromere of a dicentric chromosome migrates to the opposite side of the spindle.

23
Q

Nonreciprocal Translocation

A
  • Results from unbalanced exchange of genetic material between 2 or more chromosomes.
  • There is a loss or a gain of genetic material.
  • Can be very problematic and lethal.
  • The cell will die the next time it divides.
  • Fragments will be lost with no centromere.
24
Q

45,XY,der(7)t(7;17)(q22,q11.2),-17

A

Example of a nonreciprocal translocation.

25
Q

Derivative

A
  • A translocation occurred but it is unknown where the chromosome came from.
  • Can be generated by more than one aberration within a single chromosome.

OR

-Can be a rearrangement involving 2 or more chromosomes.

26
Q

46, XX, der(7)add(7)(p22)del(7)(q22;q34)

A

Example of a Derivative

27
Q

Acrocentric Chromosomes

A
  • Have very small p arms.
  • Are highly polymorphic (can come in different sizes).
  • Were used in early forensics as identification.
28
Q

Robertstonian Translocations

A
  • Chromosomal rearrangement between 5 specific acrocentric chromosomes. (13;14;15;21;22)
  • They are constitutional.
  • They are fragile.
29
Q

Which are the only 2 Robertsonian Translocations that are survivable after child birth?

A

Trisomy 13 - Patau Syndrome

Trisomy 21 - Down’s Syndrome

30
Q

45, XX, rob(14;21)(q10;q10)

A

Example of Robertsonian Translocation

31
Q

Unbalanced Translocation

A

Loss or gain between 2 or more chromosomes.

32
Q

Balanced Translocation

A
  • Two breaks in a chromosome, or between 2 or more chromosomes, with no gain or loss. (They have swapped places.)
  • This can result in the wrong expressions occurring.
  • The increased number of cells translocated the worse the progression of the disease. Then there would be an increase in dosage or therapy due to possible resistance.
33
Q

46,XX,t(9,22,17)

A

Example of a balanced translocation.

34
Q

Anaphase Lag

A
  • Failure of a chromosome or chromatid to be incorporated into one of the daughter nuclei after cell division because of lagging during anaphase.
  • Chromosomes that do not enter a daughter cell nucleus are lost.
35
Q

What are the 2 different types of Mixoploidy?

A

Mosaicism - Derived from a single zygote

Chimerism - Derived from different zygotes

36
Q

Mosaicism

A

When an individual posses 2 or more genetically different cell lines all derived from a single zygote. (Can be found in humans.)

37
Q

Chimerism

A

When an individual has 2 or more genetically different cell lines originating from different zygotes. (Rare and not found in humans.)

38
Q

Nondisjunction

A
  • Failure of paired chromosomes to separate in anaphase of Meiosis I
  • Failure of sister chromatids to disjoin at either Meiosis II or Mitosis
  • Produces gametes with 22 or 24 chromosomes, which after fertilizations make a trisomic or monosmic zygote
  • Produces a mosaic in Mitosis
39
Q

What are the 2 possible causes of aneuploidy?

A

Nondisjunction or Anaphase Lag

40
Q

Aneuploidy

A

The presence of one or more extra chromosomes or the absence of one or more chromosomes.

41
Q

What are the 2 categories of a somatic or acquired abnormality?

A

Structural and Numerical

42
Q

Constitutional Abnormality

A

Occurs in early embryo and post fertilization (the sperm or the egg).

43
Q

The human genome has how many bases?

A
  1. 2 billion bases haplotype

6. 4 billion diploid cells

44
Q

Genes are made up of?

A
  • 20,000 to 24,000 protein coding
  • Make up 1.5% of the genome
  • “Junk” DNA
45
Q

1 Kb is how many bases?

A

1,000 bases

46
Q

1 Mb is how many bases?

A

1 million bases or 1,000 Kb

47
Q

A full diploid is how big?

A

1.5 terabytes of data.

48
Q

What is the average gene size?

A

25-30 Kb

49
Q

How small and how big can a gene be?

A

As small as a single exon (like a histone).

As big as 79 exons (2.3 Mb) (like dystrophin).

50
Q

What is the average exon size?

A

150-200 bp

51
Q 
What are the sizes of the following: 
Intron 
mRNA 
5'UTR 
3'UTR 
Coding DNA
A

Intron - 0.5 kb to 30 kb

mRNA - 2.5 kb

5’UTR - 100 bases

3’UTR - 600 to 800 bases

Coding DNA - 1.5 to 1.8 kb (500 to 600 codons)

52
Q

What is the size limit we can see under the microscope?

A

5 Megabases or 5 million bases

53
Q

What does FisH stand for?

A

Fluorescent in situ hybridization

54
Q

What are the sizes of the following:
FISH
CGH Arrays
Oligonucleotide / DNA Arrays

A

FISH - 100 to 400 kb probes / 70 kb homebrew

CGH Arrays - detects variations at 200 bp

DNA Arrays - 7 base sequences

GT4300 Advanced Medical Genetics (4 decks)

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