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Flashcards in Chromosomal Anomalies - Number Deck (37)
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1
Q

What is the telomere and what is its function?

A
  • The cap to the DNA and protein.

- It ensures replication to the tip.

2
Q

How do light bands differ from dark bands?

A

1 - Light bands replicate earlier in the S phase than dark bands.

2 - Light bands contain less condensed chromatin than dark bands.

3 - Light bands are transcriptionally active whereas dark bands are not.

4 - Light bands are gene and GC rich whereas dark bands are AT rich.

3
Q

What is comparative genomic hybridisation?

A

A method for determining the number of copies of a sequence under investigation from an array of DNA probes.

4
Q

How are chromosomal anomalies classified?

A

1 - Numerical.

2 - Structural.

3 - Relating to different cell lines (mosaicism).

5
Q

List 2 types of numerical chromosomal anomalies.

A

1 - Aneuploidies.

2 - Polyploidies.

6
Q

List 4 types of structural chromosomal anomalies.

A

1 - Translocations.

2 - Deletions.

3 - Duplications.

4 - Inversions.

7
Q

What is a reciprocal translocation?

A

Exchange of segments of non-homologous chromosomes.

8
Q

Define acrocentric.

A

Having the centromere situated so that one chromosomal arm is much shorter than the other.

9
Q

What is a Robertson translocation?

A

The fusion of the whole long arms of two non-homologous acrocentric chromosomes.

10
Q

How does the karyotype of a person with Down syndrome differ from that of a regular karyotype?

A

There is an extra chromosome 21 (trisomy 21).

11
Q

List 5 symptoms of triple X syndrome.

A

1 - Weak muscle tone.

2 - Increased height.

3 - Kidney abnormalities.

4 - Epicanthal folds.

5 - Widely spaced eyes.

12
Q

What do the letters ‘p’ and ‘q’ signify?

A
  • ‘p’ is the short arm of a chromosome.

- ‘q’ is the long arm of a chromosome.

13
Q

What is the cause of fragile X syndrome?

A
  • A mutation in the FMR1 gene.

- FMR1 is a protein that regulates the production of other proteins and plays a role in the development of synapses.

14
Q

How does the karyotype of a person with Klinefelter syndrome differ from that of a regular karyotype?

A

Males have an extra X chromosome (XXY).

15
Q

List 5 symptoms of Klinefelter syndrome.

A

1 - Taller than average stature.

2 - Longer legs.

3 - Shorter torso.

4 - Broader hips.

5 - Absent, delayed or incomplete puberty.

16
Q

List 3 autosomal abnormalities and describe their karyotypes.

A

1 - Down syndrome: 47, XX + 21.

2 - Edwards syndrome: 47, XX + 18.

3 - Patau syndrome: 47, XX + 13.

17
Q

List 4 sex chromosome abnormalities and describe their karyotypes.

A

1 - Turner syndrome: 45, X.

2 - Klinefelter syndrome: 47, XXY.

3 - Jacob syndrome: 47, XYY.

4 - Triple X syndrome: 47, XXX

18
Q

Why is it important to look for miscarriages when analysing a family tree?

A

Because chromosomal findings are common in early spontaneous abortions.

19
Q

Why do the first individuals in the family line with a Robertsonian translocation not experience symptoms?

What is the danger of being a carrier of a Robertsonian translocation?

A
  • Because they still have the normal number of chromosomes. They are just arranged differently.
  • The danger is when both the robertsonian translocation (e.g. t(14q21q)) and one of the other non-translocated genes (e.g. 14 or 21) are inherited together (creates an aneuploidy as gametes only need one copy of any chromosome).
20
Q

List 2 hypotheses that explain why having multiple copies of normal genes causes aneuploidy phenotypes.

A

1 - Gene dosage effect.

2 - Amplified developmental instability.

21
Q

What is the gene dosage effect?

A

A hypothesis that the features of a syndrome are caused by having 1.5x the normal amount of specific gene products.

22
Q

What is amplified developmental instability?

A

A hypothesis that the features of a syndrome are caused by the overall effect of imbalance on development.

23
Q

List 3 ways in which gene expression can be affected.

A

1 - Regulation of transcription of individual genes.

2 - Differential splicing of transcripts.

3 - Multiple genes acting together in developmental pathways.

24
Q

How do we determine which genes are acting when?

A

By using in-situ hybridisation (using specially designed antisense RNA).

25
Q

What is non-disjunction?

A

Where chromosomes do not split evenly during meiosis, resulting in disomic gametes and nullisomic gametes.

26
Q

Is the meiotic error of Down syndrome more likely to be due to maternal or paternal error?

A

Maternal.

27
Q

Is the meiotic error of Edwards syndrome more likely to be due to maternal or paternal error?

A

Maternal.

28
Q

Is the meiotic error of Patau syndrome more likely to be due to maternal or paternal error?

A

Maternal.

29
Q

Is the meiotic error of Turner syndrome more likely to be due to maternal or paternal error?

A

Paternal.

30
Q

Is the meiotic error of Triple X syndrome more likely to be due to maternal or paternal error?

A

Maternal.

31
Q

Is the meiotic error of Klinefelter syndrome more likely to be due to maternal or paternal error?

A

Neither (equal).

32
Q

Is the meiotic error of Jacob syndrome more likely to be due to maternal or paternal error?

A

Paternal (never maternal).

33
Q

Why do genetic abnormalities appear to be associated with an increase in maternal age?

A
  • There is a possible lengthy interval between the onset and completion of meiosis in females.
  • Accumulating effects on the oocytes during this phase may damage the cell’s spindle formation and repair mechanisms.
34
Q

List 2 symptoms of Edward syndrome.

A

1 - Heart malformations.

2 - Kidney malformations.

35
Q

List 3 symptoms of Patau syndrome.

A

Affects midline formations:

1 - Incomplete lobatino of the brain.

2 - Cleft lip.

3 - Congenital heart disease.

36
Q

List 3 symptoms of Klinefelter syndrome.

A

1 - Infertility.

2 - Poorly developed secondary sexual characteristics.

3 - Tall height.

37
Q

List 3 symptoms of Turner syndrome.

A

1 - Short stature.

2 - Primary amenorrhoea (absence of menstrual period).

3 - Coarctation (narrowing) of the aorta.