Week 11 Flashcards
Cytogenetics is the study of ____________
chromosomes
A chromosome is a single _________
DNA molecule
What is the letters to represent the short arm of a chromosome and the long arm?
Short arm = p for petit
Long arm = q
Attached to the backbone of DNA are nitrogen containing bases • Purines • Pyrimidines what are contained in these bases?
- Purines = (A) adenine, (G) guanine
* Pyrimidines = (C) cytosine, (T) thymidine
Number of chromosomes in dividing somatic cell =
Gametes contain a single copy of each chromosome =
46
23
• Diploid number (2n) = 46 -Created by mitosis
• Haploid number (n) = 23 - Created by meiosis
DNA mutations can be inherited of acquired. What some examples of acquired DNA mutations?
- Radiation
- Toxins
- Diet
- Infection
Some disorders are due to a single altered or missing gene. What is one example of single-gene disorders?
Sickle Cell Anaemia
Are most cancers are genetic or inherited in origin?
genetic
Most are acquired genetic mutations
• The mutation will be present in clones of the abnormal cell line
A gene that has potential to cause cancer is called a __________
Oncogene
What genes protect cells from one step in oncogenic pathway?
Tumour suppressor genes
Chromosome preparation requires cells with inherently high mitotic rate. Where would the sample be most likely taken from?
• Bone marrow
What is added to peripheral blood to stimulate cells to divide in culture?
mitogens
Which mitogens are used to stimulate T cells and B cells?
- Phytohaemaglutinin T cells
* Pokeweed mitogen B cells
What is added to disrupts attachment of chromosome to mitotic spindle and arrests cell division in metaphase?
colcemid
What is added so that the chromosomes spread?
hypotonic KCl
Quinacrine mustard attaches to which parts of the chromosome? tip: this is called Q banding, there is a wide range of other subsequent banding techniques.
Binds to A-T rich parts of chromosome
adenosine and thymine
List four diseases chromosome banding could be used for.
AML, MDS, ALL and CML
MDS= Myelodysplastic syndromes (Matt Damon)
What are some short comings of chromosome banding?
- Limited resolution- small deletions cannot be seen
- Cells must be proliferating
- Long time - Takes 48hrs at least
- Labour-intensive
Where is gene described as 8q15 located? • Which chromosome? • Which arm? • Which region? • Which band?
Chromosome - 8
Long arm (q)
Region 1
Band 5
How do you describe the karyotype for males and for females?
Males 46XY
Females 46XX
How would a trisomy 8 in a male be written?
47,XY,+8
How would 20 cells examined in a female, trisomy 8 found in 10 cells and the other 10 were normal?
47,XX, +8 [10] / 46, XX, [10]
How would you write a translocation of the following:
• Short arm of chromosome 12 at region 1 band 3
• Long arm of chromosome 21 at region 2 band 2
t(12;21)(p13;q22)
What does Aneuploidy mean?
Abnormal number of chromosomes
What does Polyploidy mean?
Chromosome number higher than 46
What are some examples of a Balanced rearrangement of chromosome regions?
- Translocation
* Inversion
What are some examples of a Unbalanced rearrangement of chromosome regions?
- Deletion
* Insertion
In situ hybridisation is a combination of what two analysis?
Combines molecular methods with karyotype analysis
Can an In Situ Hybridisation probe target
• Repetitive DNA sequences
• Whole chromosomes
• Specific locus
Yes
FISH stands for what?
Fluorescent In Situ Hybridisation
Process of FISH
• Patient DNA is denatured so strands separate
• Target DNA anneals if the complementary sequences are present
• Fluorophore is bound to target DNA
• Wash away unbound probe
• Counterstain
• Fluorescent microscopy
Just know
In FISH do cells need to be dividing (metaphase) or do the have to be non-dividing (interphase) cells, or can be they be in either to be analysed?
Can be in either
What are some disadvantages of FISH?
- Pre-knowledge about suspected aberrations is necessary for selection of specific probes
- Only a limited number of loci can be analysed
G banding refers to the technique of staining chromosomes:
a) To isolate those in the G group (chromsomes 21 and 22)
b) To identify those cells in the G0 resting stage
c) Using giemsa stain
d) To emphasise areas high in guanine residues
c) Using giemsa stain
Which of the following compounds is used to halt mitosis in metaphase for chromosome analysis?
a) Imatinib
b) Fluorescein
c) Trypsin
d) Colcemid
d) Colcemid
One arm of a chromosome has 30 bands. Which band would be nearest the centromere?
a) Band 1
b) Band 15
c) Band 30
a) Band 1
Which of the following is not an advantage of FISH?
a) It can be used on non-dividing cells
b) It can be used on paraffin embedded tissue
c) It can detect mutations that do not result in abnormal banding patterns
d) It must be performed on dividing cells
d) It must be performed on dividing cells
Which of the following types of mutations would probably not be detectable with cytogenetic banding techniques?
a) Point mutation deletion resulting in a single amino acid substitution
b) Transfer of genetic material from one chromosome to another
c) Loss of genetic material from a chromosome that does not appear on any other chromosome
d) Duplication of a chromosome resulting in 3n of that genetic material
a) Point mutation deletion resulting in a single amino acid substitution
Which of the following describes a chromosomal deletion?
a) Point mutation resulting in a single amino acid substitution
b) Transfer of genetic material from one chromosome to another
c) Loss of genetic material from a chromosome that does not appear on any other chromosome
d) Duplication of a chromosome resulting in 3n of that genetic material
c) Loss of genetic material from a chromosome that does not appear on any other chromosome
The chromosome analysis performed on a patient’s leukaemic cells is reported as 47,XY,+4,del(5)(q31)[20]
• This patient’s cells have which of the following mutations?
a) Loss of the entire chromosome 31
b) Loss of the entire chromosome 5
c) Loss of a portion of the short arm on chromosome 4
d) Loss of a portion of the long arm on chromosome 5
d) Loss of a portion of the long arm on chromosome 5
The chromosome analysis performed on a patient’s leukaemic cells is reported as 47,XY,+4,del(5)(q31)[20]
• What other mutation is present in this patient’s cells?
a) Polyploidy
b) Tetraploidy
c) An extra chromosome 4
d) Four copies of chromosome 5
c) An extra chromosome 4 referred to as a trisomy
What does Tetraploidy mean?
92 chromosomes in each cell
