Lecture 1 Flashcards
Ploidy Range
The number of sets in an organism while applying the formula: Ploidy level (Haploid Number) +/- 11
Haploid Range
23 +/- 11 = 12-34
Diploid Range
46 +/- 11 = 35-57
Triploid Range
69 +/- 11 = 58-80
Tetraploid Range
90 +/- 11 = 81-103
Composite Karyotype
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.
Single Cell Evolution
- 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.
Clonal Evolution
- 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.
Ring Chromosomes
- 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.
Isochromosomes
- 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.
What is a good example of an isochromosome?
Turner Syndrome
Duplication
- 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.
Paracentric Inversion
- 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.
Pericentric Inversion
- 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.
Inversions
- 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.
What are the two types of Inversions?
Pericentric - Breaks on both arms
Paracentric - Breaks on only one arm
Deletion
- Results in a loss of genetic material.
- Is the most common.
- Functional monosomy.
- Can be terminal or interstitial.
Insertions
- Parts of a chromosome inserted into another chromosome.
- Can be direct or inverted.
- Can be Intra or Inter.
What are the 2 types of direct Insertions?
Intra - Insertion within the same chromosome
Inter - Insertion between 2 or more chromosomes
Telomeres
- Prevent the chromosomes from forming a circle or rings.
- The shorter a telomere is the older the person is.
Dicentric Chromosomes
- 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.
Anaphase Bridge
Occurs when each different centromere of a dicentric chromosome migrates to the opposite side of the spindle.
Nonreciprocal Translocation
- 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.
45,XY,der(7)t(7;17)(q22,q11.2),-17
Example of a nonreciprocal translocation.
Derivative
- 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.
46, XX, der(7)add(7)(p22)del(7)(q22;q34)
Example of a Derivative
Acrocentric Chromosomes
- Have very small p arms.
- Are highly polymorphic (can come in different sizes).
- Were used in early forensics as identification.
Robertstonian Translocations
- Chromosomal rearrangement between 5 specific acrocentric chromosomes. (13;14;15;21;22)
- They are constitutional.
- They are fragile.
Which are the only 2 Robertsonian Translocations that are survivable after child birth?
Trisomy 13 - Patau Syndrome
Trisomy 21 - Down’s Syndrome
45, XX, rob(14;21)(q10;q10)
Example of Robertsonian Translocation
Unbalanced Translocation
Loss or gain between 2 or more chromosomes.
Balanced Translocation
- 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.
46,XX,t(9,22,17)
Example of a balanced translocation.
Anaphase Lag
- 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.
What are the 2 different types of Mixoploidy?
Mosaicism - Derived from a single zygote
Chimerism - Derived from different zygotes
Mosaicism
When an individual posses 2 or more genetically different cell lines all derived from a single zygote. (Can be found in humans.)
Chimerism
When an individual has 2 or more genetically different cell lines originating from different zygotes. (Rare and not found in humans.)
Nondisjunction
- 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
What are the 2 possible causes of aneuploidy?
Nondisjunction or Anaphase Lag
Aneuploidy
The presence of one or more extra chromosomes or the absence of one or more chromosomes.
What are the 2 categories of a somatic or acquired abnormality?
Structural and Numerical
Constitutional Abnormality
Occurs in early embryo and post fertilization (the sperm or the egg).
The human genome has how many bases?
- 2 billion bases haplotype
6. 4 billion diploid cells
Genes are made up of?
- 20,000 to 24,000 protein coding
- Make up 1.5% of the genome
- “Junk” DNA
1 Kb is how many bases?
1,000 bases
1 Mb is how many bases?
1 million bases or 1,000 Kb
A full diploid is how big?
1.5 terabytes of data.
What is the average gene size?
25-30 Kb
How small and how big can a gene be?
As small as a single exon (like a histone).
As big as 79 exons (2.3 Mb) (like dystrophin).
What is the average exon size?
150-200 bp
What are the sizes of the following: Intron mRNA 5'UTR 3'UTR Coding DNA
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)
What is the size limit we can see under the microscope?
5 Megabases or 5 million bases
What does FisH stand for?
Fluorescent in situ hybridization
What are the sizes of the following:
FISH
CGH Arrays
Oligonucleotide / DNA Arrays
FISH - 100 to 400 kb probes / 70 kb homebrew
CGH Arrays - detects variations at 200 bp
DNA Arrays - 7 base sequences
