Genetics

Question 1

Fluorescent staining

Answer 1

For chromosomes within the nucleus e.g. chromosome 11

Question 2

How a chromosome is recognised

Answer 2

• Banding pattern with specific stains
• Length
• Position of centromere

Question 3

Anueploidy

Answer 3

Whole or extra missing chromosome

Question 4

Translocation

Answer 4

Rearrangement of chromosomes

Question 5

Robertsonian translocation

Answer 5

Two acrocentric chromosomes stuck end to end

Question 6

Robertsonian translocation and pregnancy?

Answer 6

Increases risk of trisomy

(because of meiosis etc & you have this double decker chromosome = 2. So 2 + 1 (1 is normal) = 3

Question 7

Most common form of robertsonian translocation

Answer 7

Most common robertsonian translocations are between chromosomes 14 and 21

Question 8

Recurrence of Down Syndrome

Answer 8

• Approximately 1% if child has primary trisomy 21

- Higher if caused by robertsonian translocation

Question 9

47 XY + 18

so 47 chromosomes where you have 3 copies/trisomy 18

Answer 9

Edward Syndrome

Question 10

45X

Answer 10

Turner syndrome

Question 11

47XXX

Answer 11

Triple x

Question 12

47XXY

Answer 12

Klinefelters

Question 13

Trisomy 18

Answer 13

Edward syndrome

Question 14

Why is X chromosome aneuploidy better tolerated?

Answer 14

X inactivation (i.e. only ever 1 active X chromosome in cells at any one time)

Question 15

Reciprocal translocations: alternate, adjacent-1, adjacent-2. Which one would you want?

Answer 15

Alternate –> normal and balanced.

Adjacent-1 and adjacent-2 will result in imbalance

Question 16

Reciprocal translocation reproductive risks

Answer 16

for most translocations, ~50% of conceptions will have either normal chromosomes or the balanced translocation

unbalanced products result in –
miscarriage (large segments)
dysmorphic delayed child (small segments)

Question 17

How could you detect translocations?

Answer 17

FISH

Question 18

22q11 deletion?

Answer 18

DiGeorge syndrome
The result of the 22q11.2 deletion is a range of embryonic developmental disruptions involving the head, neck, brain, skeleton, and kidneys. Portions of the heart, head and neck, thymus, and parathyroids derive from the third and fourth pharyngeal pouches, and a developmental field defect results from the chromosomal deletion. This, in turn, leads to hypocalcemia and variable T-cell deficiency.

Question 19

How could you detect diGeorge syndrome?

Answer 19

FISH (i.e. band/probe-y bit won’t show up)

Question 20

HER2 protein in cancer and looking at it?

Answer 20

HER2 protein over expression found in breast cancer.
Because proteins are made by genes then you could look at the genes.
Look at the genes by using FISH :D

Question 21

Genome wide investigation

Answer 21

Array CGH

Question 22

Specific loci or chromosomes

Answer 22

Quantitive PCR

Question 23

Prenatal cytogenetic investigation

Answer 23

QF-PCR

quantitive fluorescent PCR

Question 24

Why is QF-PCR good?

Answer 24

Allows you to copy small sections of DNA in order to precisely quantify the amount of DNA present

Question 25

Is array CGH DNA based?

Answer 25

Yeah, it compares sample DNA to control DNA

Reflects the underlying chromosomes (i.e. if they have extra/missing DNA)

Question 26

Mosaic conditions

Answer 26

Mosaic Down Syndrome
Mosaic Klinefelter Syndrome
Mosaic Turner Syndrome
(from internet)

Question 27

Types of mosaicism

Answer 27

Somatic mosaicism

Gonadal mosaicism

Question 28

What is mosaicism?

Answer 28

cells within the same person have a different genetic make up. This condition can affect any type of cell

Question 29

GONADAL MOSAICISM

Answer 29

ommoner in some diseases
Duchenne Muscular Dystrophy
Osteogenesis Imperfecta

Causes recurrence risk for autosomal dominant conditions even if parent is unaffected

Question 30

In which conditions is gonadal mosaicism more common?

Answer 30

Duchenne muscular dystrophy

Osteogenesis imperfecta

Question 31

Significance of gonadal mosaicism

Answer 31

Gonadal/germline mosaicism is a likely explanation of the rare situations where a person without a dominant condition can have two children with the same autosomal dominant condition

Question 32

A person without an autosomal dominant condition has two children with one, what could be the cause?

Answer 32

Gonadal mosaicism

Question 33

Abnormally short chromosome 22 with translocation of chromosome 9?

Answer 33

Philadelphia chromosome

• causes chronic myeloid leukaemia
• treat with Imatinib (tyrosine kinase inhibitor)

Question 34

Treatment for Her2 amplification

Answer 34

Trastuzumab

monoclonal antibody

Question 35

Trastuzumab

Answer 35

Monoclonal antibody used to treat HER2 amplification