Chromosomes and abnormalities

Question 1

what phase of mitosis is most useful for chromosome analysis and why?

Answer 1

Metaphase, as the chromosomes are condensed

Question 2

describe the 7 steps of karyotyping?

Answer 2

1. sample is added to a culture medium - + PHA
2. incubate at 37C
3. Add Colcemid, inactivates spindle fibre formation
4. add hypotonic solution, swells the cell so that the chromosomes are more spread
5. fix the cells and spread on slide by dropping
6. stain
7. bandind

Question 3

how does colcemid inactivate spindle fibre formation?

Answer 3

binds to tubulin protein

Question 4

what’s an ideogram?

Answer 4

a diagram of a chromosome at different resolutions, shows banding

Question 5

what does metacentric mean?

Answer 5

the centromere is near the centre

Question 6

what does centric mean?

Answer 6

the centromere is in the centre

Question 7

what does acrocentric mean?

Answer 7

the centromere is far away from the centre.

Question 8

what does trisomy mean?

Answer 8

one extra chromosome

Question 9

what does monosomy mean?

Answer 9

loss of one chromosome

Question 10

what does polyploidy mean?

Answer 10

mutiple extra chromosomes

Question 11

what is translocation?

Answer 11

a chromosomal segment is moved from one position to another either on the same chromosome or a different chromosome

Question 12

what is inversion?

Answer 12

a region on a chromosome is inverted

Question 13

what is duplication?

Answer 13

a bit of genetic material is duplicated

Question 14

whats a nullsomic gamete?

Answer 14

a cell with no genetic material in it

Question 15

Edwards syndrome causes –>

Answer 15

trisomy 18, short life expectancy a year or less

Question 16

Patau syndrome causes –>

Answer 16

trisomy 13, significant cleft lip/palate, eye problems, short life expectancy 3 years or less

Question 17

in order describe these conditions -

1. 47 XXY
2. 47 XXX
3. 45 X

Answer 17

1 = Klinefelter
2 = triple X
3 = Turner

Question 18

whats a triploid karyotype?

Answer 18

three copies of every single chromosome - significant growth retardation, life expectancy less than a week

Question 19

whats a reciprocal translocation?

Answer 19

exchange of material between non-homologous chromosomes

Question 20

what segregation?

Answer 20

where chromosomes separate

Question 21

what is robertsonian translocation?

Answer 21

between chromosomes where the centromere is right at the top

Question 22

what does FISH stand for?

Answer 22

Fluorescent in situ hybridisation

Question 23

how does FISH work?

Answer 23

DNA probed with fluorophores
hybridised directly to the chromosome targeted for a specific region/gene
used to count genes during interphase

Question 24

what is a microarray?

Answer 24

an analytical method that improves the resolution for the detection of cytogenetic abnormalities.

Question 25

how does a microarray work?

Answer 25

mix DNA on a slide
contains millions of probes
ratio of colours determines the amount of DNA

Question 26

what is a constitutional abnormality?

Answer 26

a abnormality that affects every cell - it is inheritable and occurs at gametogenesis

Question 27

what is an acquired abnormality?

Answer 27

a change that occurs during life, restricted to malignant tissue and isn’t inheritable

Question 28

what is a fusion gene?

Answer 28

a hybrid gene created when 2 portions of 2 different genes join to form a new protein. or by joining a gene to a different promoter

Question 29

what is deregulation?

Answer 29

juxtaposition of gene to a regulating gene - altering regulation which can increase transcription and cause neoplastic growth

Question 30

what is gene amplification?

Answer 30

when a gene is over produced in a cell

Question 31

what is nondisjunction?

Answer 31

the failure of chromosomes to separate during meiosis phase 1 or phase 2

Question 32

what does the Poly-A-Tail do?

Answer 32

stops RNA breaking down

Question 33

what is alternative splicing?

Answer 33

when an extra exon is added or removede in a tissue (usually 10 so abnormal would be 9 or 11)

Question 34

what is anticipation?

Answer 34

when a repeat gets bigger when passed on a generation so the condition manifests earlier and more severe than before.

Question 35

what’s a trinucleotide repeat and give examples?

Answer 35

lots of repeated trinucleotides.

Huntingtons CAG, Myotonic dystrophy CTG, Fragile X CGG)

Question 36

what is a missense?

Answer 36

when one amino acid is exchanged for another (can be pathogenic or not)