Brainscape's Knowledge GenomeTM

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


See full index

MRCOG Part one > Genetics: Single gene and chromosome abnormality > Flashcards

Genetics: Single gene and chromosome abnormality Flashcards

1
Q

What is the meaning of haploid cells?

A

Haploid cells only contain 23 chromosomes, the germ cells.

All somatic cells have 46 chromosomes, the diploid number

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

Describe what happens in meiosis 1

A
  1. DNA duplication of chromosomes
  2. Homologous chromosome recombinant with non identical chromatids (mixes maternal & paternal DNA)
  3. Duplicated chromosomes then split to form 2 new daughter cells (with 2 x chromatids in each)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe what happens in meiosis 2

A

Single chromosome split into sister chromatatids & pulled to side of cell before cytokinesis.

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

How many daughter cells are made from one dividing germ cell during meiosis

A

4 - each containing 23 chromosomes

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

What is the difference between the development of the germ cell between ovum and sperm after meiosis

A

Female: 3 daughter cells form polar bodies and will not survive, 1 becomes ovum
Men: All develop into spermatozoa

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

What is the meaning of aneuploidy?

A

Abnormality of number of chromosomes

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

What are the main mechanisms resulting in aneuploidy

A

Non-disjunction

Translocation

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

How does nondisjunction occur?

A

Pairs of homologous chromosomes at meiosis 1 or sister chromatids during mitosis do not separate so both chromosomes are passed onto on daughter cell (trisomy), whilst one is left missing one chromosome (monosomy)

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

Name some trisomy conditions

A 
Downs syndrome 
Edwards Syndrome
Patau syndrome 
Klienfelter (XXY)
Triple X syndrome (XXX)
XXY syndrome (XXY)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What % of does syndrome is caused by nondisjunction?

Other cause?

A

95%

Robertsonian Translocation

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

What medical conditions are often present in those with Downs Syndrome?

A 
Learning difficulty 100%
Cardiac problems atrioventricular defects (40-50%)
Hypothyroidism 20-40%
Dementia 10-15%
Acute Lymphoblastic anaemia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What chromosome is trisomy in edwards syndrome?

A

18

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

What are the clinical features of Edwards Syndrome?

A 
Babies likely to die within 1 year
Profound learning difficulty 
Congential heart disease (90%, VSD)
Facial clefts
Spina bifida 
Clenched hands
Rockerbottom feet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What chromosome does Patau syndrome effect?

A

13

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

What are the clinical features of patau syndrome?

A 
High rate miscarriage 
Profound learning difficulty
Congential heart disease 
Postaxial polydactyly 
Cleft palate
Microphthalmia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Clinical features of klinefelter syndrome

A

Slightly descreased IQ
Tall stature
Infertility
Transient gynaecomastia

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

Whats the risk of nondisjunction at 20 vs 40 yrs

A

20: 1 in1500
40: 1:100

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

Name a monosomy resulting from nondisjunction

A

Turners syndrome 45X

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

What are the clinical features of Turner syndrome?

A

Mildly Lower IQ
Many do not survive due to fetal hydrous
High risk of miscarriage
Consider NT >4mm

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

What is the difference between balanced and unbalanced reciprocal translocation?

A

Chromosome rearrangement between 2 nonhomologus chromosomes.

Balance: No phenotypic consequence
Non balances: 1 chromosome with missing genetic material (monosomy) and 1 with duplicate genetic material (trisomy)

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

If a parent with balanced translocation has children with partner with normal chromsomes what are the possible outcomes

A
  • 25% normal chromsome
  • 25% balanced translocation
  • 50% unbalanced translocation → risk sport miscarriage or go to term with child with high risk learning difficulty etc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Explain robertsionian translocations

A

Chromsome rearrangement that involves fusion of the long arms of 2 afrocentric chromosome and their short arms are lost.

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

Which chromosomes can have robertsonian translocations?

A

13, 14, 15, 21 & 22

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

13q, 14q and 14q,21q are the most common robertsoninan translocations, which conditions are these?

A

13q14q patau

14q 21q downs

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

What is imprinting and which chromosomes are vulnerable?

A

One parent allele is preferentially silenced

14&15

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

What conditions is paternal uniparental disomy (UPU15)

Some features?

A

Angelman syndrome characteristic face and ataxic fain severe learning difficulty

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What conditions is maternal uniparental disomy (UPU15)

Some features?

A

Prader-willi poor feeders in neonatal period, insatiable appetite from childhood, hypotonic and short, learning difficulty

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What technique is used to identify micro deletions or micro duplications?

A

aCGH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

In micro deletions what mechanisms abrogate gene function:

A 
missense mutation
truncating mutation (frameshift, nonsense)
Splice site 
partial gene deletion
whole gene deletion 
triplet repeat expansion
30
Q

What common conditions are from triplet repeat expansion?

A

Huntingdons, myotonic dystrophy, fragile x

31
Q

Which micro deletion is williams syndrome

A

7q11

32
Q

what are the features of williams syndrome

A

mild/severe learning
Cardiac aortic/pulmonary stenosis
renal artery stenosis
cocktail party personality

33
Q

which micro deletion if diGeorge

A

22q11

34
Q

what are the features of diGeorge

A 
Leanrind difficulty 
cardiac fallot, vid
short 
cleft palate 
low calcium
35
Q

4 ways genes can be inherited?

A 
AD
AR
X linked r
X linked d 
mitochondrial
36
Q

Main features of tuberous sclerosis

A

AD
multisystem, cutaneous (shagreen patches)
neurological (brain hamartoma - seizure)
prenatal: rhabdosacroma

37
Q

Main features of neurofibromatosis type 1

A

AD
Cafe-au-let spots
neurofibromatoma
inguinal freckling and optic glioma

38
Q

Main features of HNPCC

A

AD

cancer: colon, endometrium, gastric and ovarian

39
Q

Main polycystic kidney disease

A

AD
Cysts in the kidney, liver, pancreas & spleen
CV abnormality intracranial anrueysm mitral valve prolapse

40
Q

Main features of haemochromatosis

A

AR

excess iron absorption in liver, pancreas and skin (cirrhosis, DM, bronze skin)

41
Q

Main features of alpha 1 antitrypsin

A

AR

no elastase, emphysema at young age and cirrhosis

42
Q

congenital adnreal hyperplasia (21 hydroxyls deficiency)

A

AR
Unable to synthesis cortisol
female virilisation
precocious puberty +/- salt wasting

43
Q

Main features of duchenne muscular dystrophy

A

X linked R

Progressive myopathy. death in 3rd decade resp failure

44
Q

Main features of Haemophilia A

A

X linked R

Deficiency factor VIII, abnormal clotting

45
Q

Main features of Fragile X syndrome

A

X linked R
Expansion of CGG
Learning difficulty and appearance

46
Q

What is the likely outcome for a male fetus that inherits an X linked dominant condition

A

spent loss of pregnancy

early neonatal death

47
Q

Main features of Rett Syndrome

A

Cognitive regression and learning difficulty

hand wringing, sterotypical movement

48
Q

At what weeks can’t the nuchal translucency be tested?

A

11-14 weeks

49
Q

What other findings other than nuchal translucency in 1st trimester are associated with trisomy 21

A

Absent or hypoplastic nasall bone

Absant or reversed A wave in blood flow of ductus arterisosis

50
Q

What is included in the triple test?

How accurate is it for detecting trisomy 21

A

NT, bHCG and PAPPA

90%

51
Q

Positive finding of triple test?

A

High NT
high bHCG
low PAPPA

52
Q

What tests are perfromed in the triple screen

A

aFP
bHCG
Estriol
70%

53
Q

Findings of triple test in Downs

A

afp & estriol low

bHCG high

54
Q

finding triple test in edwards

A

all low

55
Q

high alpha fetoprotein is associated with what?

A

Neural tube defects

56
Q

What tests are in the quadruple test? Accuracy

A 
aFP
bHCG
Estriol 
Inhabin 
81%
57
Q

when is triple test/quadruple test performed

A

16-18 weeks

58
Q

What is cell-free fetal DNA testing? What is it tested for?

A

Non invasive, small amount fetal DNA used to determine gender, rhesus status + trisomy 13,18,21

59
Q

When can CVS happen?

What is aspirated?

A

11 weeks-14weeks

Placental tissue

60
Q

What is the difference in sampling cytotrophoblast vs mesenchymal cells during CVS?

A

Cytotrophoblasts are rapidly dividing, results in 2-3 days

mesenchymal cells 1-3 weeks but more accurate

61
Q

Risk of false positive in CVS & why

A

1.5% Placental mosaicism, present in placenta but not fetal tissue

62
Q

When is amniocentesis performed?
When cells are tested?
How long for result & why?

A

15 weeks
Amniocytes (in amniotic fluid), fetal skin, urinary tract & GI tract
1-3 weeks - no rapidly dividing cells.

63
Q

Miscarriage rate of amniocentesis and CVS

A

1%

64
Q

When can cordcentbesis be performed?

What can is test for?

A

From 18 weeks
anaemia, prenatal infection
1-2% misc rate

65
Q

Which molecular genetic techniques measure gene dosage at particular locations in the genome?

A

FISH (Fluorescence in situ hybridisation)
QF PCR (Quantative fluorescence polymerase chain reaction)
MLPA (Multiplex ligation probe aplification)

66
Q

Which molecular genetic techniques measure gene dosage over the entire genome?

What is the benefit of this over the other methods mentioned?

A

aCGH (microarray comparative genetic hybriddisation)

Can also detect micro deletions or micro duplications as we’ll as aneuploidy

67
Q

What is the lifetime risk of developing ovarian cancer in the general population?
What % is due to BRCA1&2 genes?

A

1 in 70

6-8%

68
Q

Lifetime risk BRCA1 in developing breast & ovarian cancer?

A

Breast 60-90%

Ovarian 40-60%

69
Q

Lifetime risk BRCA2 in developing breast & ovarian cancer?

A

Breast 45-85%

Ovarian 10-30%

70
Q

What % of overall breast cancers are due to BRCA1&2

A

2%

71
Q

In HNPCC lifetime risk of endometrial cancer risk?

A

50%

72
Q

In Peutz-Jegher syndrome, what is the lifetime risk of endometrial cancer?

A

40%
30% bowel cancer
- pigmented macules in mucus membranes and skin + GI

MRCOG Part one (28 decks)

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