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MRCOG Part One > Genetics > Flashcards

Genetics Flashcards

1
Q

What is a eukaryote?

A

complex animal/plant cells that have a nucleus surrounded by a defined membrane

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2
Q

Types of cell organelle:

A

Nucleus, Endoplasmic reticulum (rough and smooth), Golgi complex, mitochondria, lysosome/peroxisomes, cytosol

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3
Q

Name the 3 Prostanoids and what they are catalysed by

A

Prostaglandins, Prostacyclins, Thromboxanes
Catalysed by Prostaglandin H2 Synthase otherwise known as CYCLOOXYGENASE 1+2

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4
Q

Where is COX 1 found?

A

Tissues that constantly produce prostaglandins e.g Stomach Mucosa

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5
Q

Where is COX 2 found?

A

Areas of inflammation

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6
Q

What type of COX are Aspirin and NSAIDs sensitive towards?

A

Aspirin = COX 1
NSAIDs = COX 1 and 2 - newer NSAIDs more sensitive towards COX 2 only

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7
Q

Name 4 types of Cell Surface Receptor

A

1) G protein coupled receptors
2) Ion channel receptors
3) Tyrosine kinase linked receptors
4) Receptors with intrinsic enzyme activity

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8
Q

Name 4 types of cell-cell adhesion & their properties

A

1) Cadherins - homphilic, binds using Calcium
2) Immunoglobulins
3) Integrins - adhesion but also aids cell communication
4) Selectins - carbohydrate links = WEAK

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9
Q

Name 4 types of Cell junction type

A

1) tight junctions - impermeable
2) adherens and desmosome - provides rigidity
3) hemidesmosomes - connects via intermediate filaments of cells
4) Gap junctions - cytoplasms of adjacent cells join via proteins to form channels

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10
Q

What is a nucleotide made up of?

A

1) sugar molecule (ribose or deoxyribose) - a 5 carbon sugar
2) Nitrogenous base (A, G, C, T)
3) phosphate group

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11
Q

Which bases pair up and how do they remain paired?

A

A&T
C&G
-bound via weak hydrogen bonds

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12
Q

What is a nucleic acid?

A

A long polymer of nucleotides that form in a 5” to 3” direction

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13
Q

Name the 3 stages of DNA replication

A

1) Unwinding by DNA helicase
2) Copying by DNA polymerase
3) rewinding by DNA Ligase

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14
Q

What is a gene and what is it made up of?

A

A stretch of nucleotides that code for a polypeptide/protein
-made up of exons (coding areas) and introns (non-coding)

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15
Q

How many human chromosome?

A

46 - 23 pairs

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16
Q

What is PCR?

A

Polymerase chain reaction
-used to amplify a specific sequence of DNA
-requires 2 primers, heat stable DNA polymerase called TAQ and a supply of nucleotides

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17
Q

What is southern blotting?

A

A laboratory technique to detect the presence and amount of a particular DNA sequence

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18
Q

What is Northern Blotting?

A

A laboratory technique to detect present and amount of a particular RNA sequence

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19
Q

What is western blotting?

A

a lab technique to detect presence and amount of a specific protein by use of protein antibodies and gel electrophoresis

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20
Q

What is Proteomics?

A

to assess structure of proteins

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21
Q

What are the 4 stages of the cell cycle?

A

Gap 1
Synthesis - replication of chromosomes
Gap 2
Mitosis

*G1, S and G2 = Interphase

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22
Q

What is Mitosis and what are its 4 stages?

A

Division of a Diploid cell to produce 2 diploid daughter cells
1) Prophase - condensation of chromosomes
2) Metaphase - chromatids align in centre of cell
3) Anaphase - separation of chromatids to opposite poles of cell through microtubule shortening
4) Telophase - nuclear envelope breaks down and reforms around each set of chromosomes

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23
Q

What is Meiosis and what are its stages?

A

Division of one diploid cell to produce 4 haploid cells - PRODUCTION OF GERM CELLS
2 overall stages - Meiosis 1 and 2
-Meiosis 1 = like mitosis but without replication of chromosomes
-Meiosis 2 = like mitosis

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24
Q

What are the 5 models of inheritance?

A

1) Autosomal Dominant
2) Autosomal Recessive
3) X linked Dominant
4) X linked Recessive
5) Mitochondrial (from maternal)

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25
Q

What are the 2 ways in which chromosomal abnormalities can occur?

A

1) Aneuploidies - the wrong number of chromosomes
2) Structural anomalies
-translocations
-inversions
-deletions
-duplications
-insertions

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26
Q

How does an Aneuploidy occur?

A

1) Nondisjunction - pair of homologous chromosomes fail to separate in Meiosis 1
2) Translocation - part of a chromosome attaches to another

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27
Q

What is Down’s Syndrome?

A

Trisomy 21
95% caused by non-disjunction (85% maternal)
3% Robertsonian Translocation (14:21)
1% Mosaicism

28
Q

What are the cardinal features of Down’s?

A

Mod/Severe learning difficulties
Raised nuchal translucency
dysmorphia (small ears, up slanting palpebral fissures, epicanthic folds)
hypotonia
VSD/ASD/AVSD
Duodenal atresia, hirchsprungs, imperforate anus
Conductive hearing loss
Risk of Alzheimers , Hypothyroid, ALL

29
Q

What is the risk of Down’s occurring?

A

1 in 700 livebirths
Risk increases with maternal age:
25 yrs = 1:1500
30yrs = 1:900
35yrs = 1:350
40yrs = 1:100
45yrs = 1:45
50yrs = 1:11

30
Q

What is Edward’s Syndrome?

A

Trisomy 18
Majority occur from Meiotic non-disjunction
1 in 3000 livebirths, M:F = 1:2

31
Q

What are the cardinal features of Edward’s?

A

Raised nuchal translucency and spina bifida
Rockerbottom feet, overlapping fingers, clenched hands
Micrognathia, cleft lip/palate
90% have VSD/ASD/PDA
Exomphalos, inguinal hernia, diaphragmatic hernia
Severe learning difficulties
Risk of mortality:
90% by 1 yr (1 month is 30%)

32
Q

What is Patau’s?

A

Trisomy 13
Risk is 1 in 5000 live births
*There is a high rate of spontaneous pregnancy loss

33
Q

What are the cardinal features of Pataus?

A

Midline defects: hypotelorism, holoprosencephaly, cleft lip/palate, scalp defects
Post-axial polydactyly
ASD/VSD
Omphaloceles
Renal abnormalities
High mortality - almost 100% by 1 month

34
Q

What is a Barr Body?

A

Lyon’s Hypothesis suggests if XX - by day 16 of embryogenesis, one X is deactivated and becomes the BARR BODY

35
Q

What is Turner’s Syndrome?

A

Sex Aneuploidy - Monosomy 45, X
1 in 2500 live female births
*High risk of miscarriage

36
Q

What are the cardinal features of Turner’s?

A

Raised NT
Cystic Hygroma/Lymphoedema
Neck webbing and short stature
Wide angle of arms and shield chest
Coarctation of the aorta
Horseshoe kidney
IQ relatively preserved

37
Q

What is Klinefelter’s Syndrome?

A

Sex aneuploidy - 47, XXY
*Often detected incidentally during CVS/Amnio, or as part of adult infertility investigations

38
Q

What are the features of Klinefelter’s?

A

Relatively preserved IQ
tall stature
infertility
transient gynaecomastia
small testes with hypogonadotrophic hypogonadism

39
Q

What is Triple X syndrome?

A

47, XXX
-slightly decreased IQ
-tall stature
-normal fertility

40
Q

What is XYY Syndrome?

A

47, XYY
-slightly decreased IQ
-tall stature
-Behavioural problems

41
Q

What is a Translocation?

A

The exchange of 2 segments of chromosome between non-homologous chromosomes

42
Q

What is a Robertsonian Translocation?

A

fusion of the long arms of two afrocentric chromosomes and loss of the short arms
Involes only the afrocentric chromosomes: 13, 14, 15, 21 and 22

43
Q

Which are the imprinting chromosomes and what conditions are associated with their deletion?

A

Imprinting genes are on chromosomes = 14 and 15
Maternal deletion 15q11-13 = Angelman (severe LD, macroglossia, ataxia, seizures)
Paternal deletion 15q11-13 = Prader Willi (severe LD, insatiable appetite and obesity, hypogonadism and hypotonia)

44
Q

What is DiGeorge Syndrome and what are the features?

A

22q11 microdeletion
Learning difficulties
Cardiac = VSD/Fallots/Aortic shortening
Short stature
cleft lip/palate, tubular nose, simple ears, narrow palpebral fissures
renal anomalies
parathyroid causing hypocalcaemia

45
Q

What is Tuberous Sclerosis?

A

Autosomal dominant condition affecting TSC1/TSC2 genes
Characterised by Angiofibromatas, brain hamartomas, cardiac rhabdomyosarcomas

46
Q

What is Marfan Syndrome?

A

Autosomal dominant condition affecting Fibrillin 1 gene
-Tall, raised arm span:height, aortic root dilatation, long fingers

47
Q

What is Neurofibromatosis?

A

Autosomal dominant condition affecting NF1 gene
-cafe au last spots, neurofibromata, optic glioma

48
Q

What autosomal dominant condition pre-disposes to Breast and Ovarian cancer?

A

BRCA1/BRCA2
-lifetime risk - breast 80%, Ovarian 40%

49
Q

What is Hereditary Non-Polypsis Colon cancer?

A

Autosomal dominant condition (also known as Lynch Syndrome) affecting MLH gene
-also predisposes to endometrial, ovarian and gastric cancer

50
Q

What is Huntington’s?

A

Autosomal dominant condition affecting Hungtingtin Gene
-causes progressive neurological deterioration and dementia

51
Q

What condition arises from autosomal dominant change with PKD1/PKD2?

A

Polycystic Kidney Disease
-systemic cysts in kidneys, liver, spleen, pancreas
-intracranial aneurysms
-mitral valve prolapse

52
Q

What is Achondroplasia?

A

Autosomal dominant condition affecting FGR3
-causes short stature with proximal limb shortening and macrocephaly

53
Q

What is Cystic Fibrosis?

A

An autosomal recessive condition affecting CFTR gene on chromosome 7
-usually F508 mutation
-causes viscous mucous = infertility, chest infections, pancreatitis/malabsorption, osteoporosis, diabetes, cirrhosis

54
Q

What is Sickle cell disease?

A

Autosomal recessive condition affecting production of the Beta chain of haemoglobin
-Adenine is substituted for Thymine resulting in Glutamic Acid switched for Valine
1 in 500

55
Q

What are the symptoms of sickle cell disease?

A

Anaemia - due to splenic haemolytic faster than RBC production
Crises including Occlusive, Acute Chest, Aplastic (parvovirus B19), splenic sequestration, haemolytic
-also causes infarction, emboli, infection, ischaemia

56
Q

What are the effects of sickle cell disease on pregnancy?

A

Miscarriage, pre-eclampsia, IUGR

57
Q

What are the treatments for sickle cell?

A

Cyanate, Hydroxyurea (activates fetal Hb), Analgesia, Penicillin, Blood transfusion, Bone Marrow transplant

58
Q

What is Thalassaemia?

A

Autosomal Recessive condition affecting the globin chains of Haemoglobin
-can be Alpha, Beta or delta
-less common = E, C, S
Seen mostly in mediterranean, Arabs and Maldivian

59
Q

What is Alpha Thalassaemia?

A

Thalassaemia of Alpha Globin chain
-severity depends on number of genes affected (there are 4)
1= silent carrier
2 = trait (mild anaemia)
3 = Hb H (moderate anaemia and splenomegaly)
4 = Bart’s Hydrops (in utero death due to tissue hypoxia and hydros fetalis)

60
Q

What is Beta Thalassaemia?

A

Thalassaemia of Beta globin gene (2)
Major = homozygous
Minor/Trait = heterozygous
Anaemia, SOB, Jaundice, Fatigue, hepatosplenomegaly, skeletal deformities due to increased erythropoiesis

61
Q

What is the treatment for Beta Thalassaemia?

A

Regular blood transfusion, Folic Acid/Vit D/Calcium, Chelation (for excess iron from transfusion), splenectomy, Bone marrow transplant

62
Q

What is Congenital Adrenal Hyperplasia?

A

Autosomal recessive condition of CYP21A2 gene resulting in deficiency of 21-Hydroxylase.
-Enzyme needed to synthesise cortisol
-Is associated with female virilisation and abnormal puberty

63
Q

Who is affected by X-Linked recessive conditions?

A

50% of sons of female carriers
ALL daughters of affected males will be carriers
no male-male transmission

64
Q

What are examples of X-Linked recessive conditions?

A

Duchenne muscular dystrophy (dystrophin)
Fragile X (FMR1)
Red-green colour blind
Haemophilia A (VIII) and B (IX) deficiency

65
Q

What is X-Linked dominant and what are some examples?

A

50% of offspring of affected females are affected
-manifests very severely in males = spontaneous pregnancy loss
E.g incontinentia pigmenti (NEMO) - causes blistering lesions, rett syndrome (MECP2) - Severe LD and cognitive regression, vitamin D resistant ricketts

66
Q

What tests are there for Trisomy 21 risk assessment in pregnancy and what would the results be to indicate high chance?

A

NT = raised >4mm
Combined = Raised NT, raised B-HCG, Low PAPP-A
Quad = A-FP, raised B-HCG, Low Unconjugated Estradiol, Raised Inhibin

67
Q
A

MRCOG Part One (2 decks)

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