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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
What are the 2 ways in which chromosomal abnormalities can occur?
1) Aneuploidies - the wrong number of chromosomes 2) Structural anomalies -translocations -inversions -deletions -duplications -insertions
26
How does an Aneuploidy occur?
1) Nondisjunction - pair of homologous chromosomes fail to separate in Meiosis 1 2) Translocation - part of a chromosome attaches to another
27
What is Down's Syndrome?
Trisomy 21 95% caused by non-disjunction (85% maternal) 3% Robertsonian Translocation (14:21) 1% Mosaicism
28
What are the cardinal features of Down's?
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
What is the risk of Down's occurring?
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
What is Edward's Syndrome?
Trisomy 18 Majority occur from Meiotic non-disjunction 1 in 3000 livebirths, M:F = 1:2
31
What are the cardinal features of Edward's?
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
What is Patau's?
Trisomy 13 Risk is 1 in 5000 live births *There is a high rate of spontaneous pregnancy loss
33
What are the cardinal features of Pataus?
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
What is a Barr Body?
Lyon's Hypothesis suggests if XX - by day 16 of embryogenesis, one X is deactivated and becomes the BARR BODY
35
What is Turner's Syndrome?
Sex Aneuploidy - Monosomy 45, X 1 in 2500 live female births *High risk of miscarriage
36
What are the cardinal features of Turner's?
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
What is Klinefelter's Syndrome?
Sex aneuploidy - 47, XXY *Often detected incidentally during CVS/Amnio, or as part of adult infertility investigations
38
What are the features of Klinefelter's?
Relatively preserved IQ tall stature infertility transient gynaecomastia small testes with hypogonadotrophic hypogonadism
39
What is Triple X syndrome?
47, XXX -slightly decreased IQ -tall stature -normal fertility
40
What is XYY Syndrome?
47, XYY -slightly decreased IQ -tall stature -Behavioural problems
41
What is a Translocation?
The exchange of 2 segments of chromosome between non-homologous chromosomes
42
What is a Robertsonian Translocation?
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
Which are the imprinting chromosomes and what conditions are associated with their deletion?
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
What is DiGeorge Syndrome and what are the features?
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
What is Tuberous Sclerosis?
Autosomal dominant condition affecting TSC1/TSC2 genes Characterised by Angiofibromatas, brain hamartomas, cardiac rhabdomyosarcomas
46
What is Marfan Syndrome?
Autosomal dominant condition affecting Fibrillin 1 gene -Tall, raised arm span:height, aortic root dilatation, long fingers
47
What is Neurofibromatosis?
Autosomal dominant condition affecting NF1 gene -cafe au last spots, neurofibromata, optic glioma
48
What autosomal dominant condition pre-disposes to Breast and Ovarian cancer?
BRCA1/BRCA2 -lifetime risk - breast 80%, Ovarian 40%
49
What is Hereditary Non-Polypsis Colon cancer?
Autosomal dominant condition (also known as Lynch Syndrome) affecting MLH gene -also predisposes to endometrial, ovarian and gastric cancer
50
What is Huntington's?
Autosomal dominant condition affecting Hungtingtin Gene -causes progressive neurological deterioration and dementia
51
What condition arises from autosomal dominant change with PKD1/PKD2?
Polycystic Kidney Disease -systemic cysts in kidneys, liver, spleen, pancreas -intracranial aneurysms -mitral valve prolapse
52
What is Achondroplasia?
Autosomal dominant condition affecting FGR3 -causes short stature with proximal limb shortening and macrocephaly
53
What is Cystic Fibrosis?
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
What is Sickle cell disease?
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
What are the symptoms of sickle cell disease?
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
What are the effects of sickle cell disease on pregnancy?
Miscarriage, pre-eclampsia, IUGR
57
What are the treatments for sickle cell?
Cyanate, Hydroxyurea (activates fetal Hb), Analgesia, Penicillin, Blood transfusion, Bone Marrow transplant
58
What is Thalassaemia?
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
What is Alpha Thalassaemia?
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
What is Beta Thalassaemia?
Thalassaemia of Beta globin gene (2) Major = homozygous Minor/Trait = heterozygous Anaemia, SOB, Jaundice, Fatigue, hepatosplenomegaly, skeletal deformities due to increased erythropoiesis
61
What is the treatment for Beta Thalassaemia?
Regular blood transfusion, Folic Acid/Vit D/Calcium, Chelation (for excess iron from transfusion), splenectomy, Bone marrow transplant
62
What is Congenital Adrenal Hyperplasia?
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
Who is affected by X-Linked recessive conditions?
50% of sons of female carriers ALL daughters of affected males will be carriers no male-male transmission
64
What are examples of X-Linked recessive conditions?
Duchenne muscular dystrophy (dystrophin) Fragile X (FMR1) Red-green colour blind Haemophilia A (VIII) and B (IX) deficiency
65
What is X-Linked dominant and what are some examples?
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
What tests are there for Trisomy 21 risk assessment in pregnancy and what would the results be to indicate high chance?
NT = raised >4mm Combined = Raised NT, raised B-HCG, Low PAPP-A Quad = A-FP, raised B-HCG, Low Unconjugated Estradiol, Raised Inhibin
67

MRCOG Part One (2 decks)

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