Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PoM > Genetics - Chromosomal Abnormalities > Flashcards

Genetics - Chromosomal Abnormalities Flashcards

1
Q

What is a karyotype?

A

Collection of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What can we use for a karyotype sample?

A

Peripheral blood, amniotic cells, CVS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

If using peripheral blood for karyotype, what must we do?

A
  • Isolate white blood cells
  • Then culture cells in presence of phytohemagglutin, which will stimulate T cell growth and differentiation.
  • Then, after 48 hours add colchicine to arrest mitosis.
  • Place cells in hypotonic solution - cause lysis
  • Stain with giemsa and observe results
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is an ideogram?

A

The distinct pattern a chromosome generates with giemsa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the p-arm?

A

Short arm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the q-arm?

A

Long arm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are g-dark bands?

A

Dark bands of chromosome which take up more gisema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are g-light bands?

A

Light bands of chromosome which take up less gisema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does 3p21 mean?

A

Region found on chromosome 3, p arm, 2nd band, 1st region of 2nd band.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why are dark bands dark?

A

They take up more gisema which is used to stain the chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is contained in dark bands?

A

Heterochromatin which contain few, more dense genes so take up more gisema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is contained in light bands?

A

Euchromatin with less, more open genes so take up less gisema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is aneuploidy?

A

Abnormal number of chromsomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the purpose of meiosis?

A

Achieve reduction of diploid to haploid
Achieve genetic variation
Enable random assortment of homologues and recombination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is non disjunction?

A

When chromosomes don’t split properly between daughter cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When does non disjunction occur?

A

Either meiosis 1 or 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does M1 non disjunction mean?

A

All daughter cells are affected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does M2 non disjunction mean?

A

Only half of the daughter cells are affected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does non disjunction always result in?

A

Either trisomy or monosomy after fertilisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the most common abnormality?

A

Sex chromosome aneuploidy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why is a sex chromosome imbalance tolerated?

A
  1. Only part of one of the X chromosomes in females in inactivated
  2. Y chromosome has few genes
  3. Pseudo autosomal region (PAR) - part of the X chromosome is not inactivated along with the X chromosome.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is trisomy 21?

A

Dow’s syndrome: 3 copies of chromosome 21

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

When do most cases of Downs arise?

A

Maternal oogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Is there paternal input in Downs?

A

Some

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What increases the risk of Downs?

A

Maternal age (positive correlation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Why is there a maternal age effect on Downs?

A
  1. Inherent vulnerability of oogenesis with age
  2. Primary oocytes are produced in utero before prophase 1 and then arrested until puberty
  3. Secondary oocytes arrest in metaphase 2 until fertilisation.
    This causes the degradation of factors which hold chromatids together during division
27
Q

Does paternal age influence aneuploidy?

A

No, however it has an effect on single gene disorders

28
Q

How do spermatocytes influence aneuploidy?

A

Primary spermatocytes undergo 23 mitotic divisions per year

29
Q

What is selfish spermatogonial selection?

A

Mutated spermatids may have an advantage over wild type spermatids

30
Q

What is a paternal but not maternal risk factor for Downs?

A

Smoking

31
Q

What is the effect of aneuploidy on pregnancy?

A

5% of still births and 50% of abortions/miscarriages are due to anueploidy

32
Q

How can we detect trisomy?

A

Prenatally

33
Q

Why is there little monosomy?

A

Poorly tolerated, trisomy is also often incompatible with life

34
Q

When do cross over chromosomes occur?

A

Prophase 1

35
Q

What does cross over do?

A

Increases genetic diversity

36
Q

What is cross over?

A

Pairs of chromosomes align, chiasma form and cross over between chromosomes occur

37
Q

How often does cross over occur?

A

1-3 times per chromosome per meiosis

38
Q

What happens when cross over goes wrong?

A

Unequal crossover can cause duplication in one chromosome and deletion in the other chromsome

39
Q

What are examples of single chromosome abnormalities?

A

Deletion
Duplication
Inversion

40
Q

What is deletion?

A

part of chromosome deleted

41
Q

What is duplication?

A

part of chromosome added onto same chromosome

42
Q

What is inversion?

A

Section of chromosome is turned upside down to sometimes cause reproductive issues

43
Q

What is insertion?

A

Two chromosomal abnormality - unidirectional manner of transfer from one chromosome to another

44
Q

What is translocation?

A

Mutual exchange where different derivative chromosomes are formed after a swap of genetic material

45
Q

What is an example of translocation mutation?

A

Philadelphia chromosome (CML)

46
Q

Are abnormalities always inherited?

A

No: many are de novo.

Some people are unidentified carriers and can have offspring who are affected

47
Q

What are microscopic deletions?

A

Deletion easily detected with microscope and staining e.g. Cri-du-chat syndrome - deletion of whole p arm of chromosome 5

48
Q

What are microdeletions?

A

Can only be seen in very high resolutio banding e.g. DiGeorge Syndrome - deletion of one sub band

49
Q

What occurs in William’s syndrome?

A

Gene on long arm of chromosome 7 is deleted

50
Q

Why can’t we use a normal karyotype for detecting William’s?

A

Too small to detect

51
Q

What can we use to detect Williams?

A

Fluorescent in situ hybridisation (FISH assay)

52
Q

What are the symptoms of Williams?

A

Long philtrum
Short, upturned nose
Supravalvular aortic stenosis
No social anxiety - friendly

53
Q

What is the result of a reciprocal duplication that occurs in the same area affected by Williams?

A

Opposite symptoms of William’s e.g. autistic traits, broad nose and short philtrum

54
Q

Phenotypically, how do duplications differ to deletion?

A

Generally, duplications have a milder phenotype than deletions

55
Q

What are the 3 classes of chromosomes?

A
    • Metrocentric - short P arm, long Q arm, centromere in centre
    • Submetacentric - short arm is considerably shorter than long arm
    • Acrocentric - short arm reduced to stalk or satellite.
56
Q

What is Robertsonian translocation?

A

When two acrocentric chromosomes lose their stalks and their long arms combine to form a derivative chromosome
Can be homologous or non homologous

57
Q

Why are most carriers of Robertsonian translocation unaffected?

A

If it occurs during development, they will have a balanced genotype and it only evolves one of each of the 2 chromosomes

58
Q

Why may carrier offspring not be affected?

A

If a carrier is homologous, they will have one normal copy of a chromosome which can still be inherited normally.

59
Q

Which chromosome pairs are most commonly affected by Robertsonian translocation?

A

13 and 14
14 and 15
14 and 21

60
Q

What is mosaicism?

A

Cells of the same population don’t contain the same chromosomes

61
Q

How may mosaicism arise?

A

Non disjunction during early development

Loss of extra chromosome in early development

62
Q

How common is mosaicism?

A

Everyone is thought to be mosaic

63
Q

What is the most common mosaic?

A

46, XX/45,X

46,XY/45,X

PoM (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions