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Case 7 Flashcards

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1
Q

What is the normal site of fertilisation?

A

Ampulla

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2
Q

When does ovulation occur?

A

14 days

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3
Q

Autosomal dominant risk of being affected?

A

0.5 * penetrance

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4
Q

Autosomal recessive risk of being affected?

A

¼ * mum carrier risk * dad carrier risk

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5
Q

What are some autosomal dominant conditions?

A 
Huntington disease
• Marfan syndrome
• Familial hypercholesterolaemia
• Spinocerebellar ataxia
• Familial adenomatous polyposis
• Hereditary breast and ovarian cancer
• Myotonic dystrophy
• Long QT syndrome
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6
Q

What are some autosmomal recessive conditions?

A
  • Cystic fibrosis
  • Phenylketonuria
  • β-Thalassemia
  • Sickle cell anaemia
  • Tay Sachs disease !!!
  • Spinal muscular atrophy
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7
Q

What are some X-linked recessive conditions?

A

Duchenne muscular dystrophy
• Haemophilia A
• Red-green colour blindness

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8
Q

X-linked recessive: Two unaffected parents. What is the chance of child having it?

A

Less than 1/2 but definitely not zero because of ‘germline
mosaicism’
Person may have more than one set of poulations of cells in their ovaries/testes

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9
Q

What is the probabilit that a healthy sibling of someone with an autosomal recessive disorder is a carrier?

A

2/3
Draw Hh and Hh
Ignore the hh as they have condition. Of three remaining options, 2 are carriers

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10
Q

What is the composition of semen?

A

• Sperm account for less than 10% of semen

o Remainder is accessory gland secretions such as Prostaglandins and fructose and amino acids

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11
Q

What does capacitation allow the sperm to get through?

A

Corona cells

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12
Q

What reaction occurs once sperm has bound to zona pellucida?

A

Acrosome reaction

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13
Q

What mediates the acrosomal reaction?

A

Ligand ZP3, a zona protein

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14
Q

Why dont all sperm undergo capacitation?

A

Would be a waste of resources - only one wins after all!§

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15
Q

Whats the space between the Zona pellucida and the corona cells?

A

Perivitelline space

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16
Q

Once you have a zygote formed, divisions occur and all the cells occupy same volume. What is each cell called

A

Blastomere

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17
Q

What is 16 cell stage called?

A

Morula

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18
Q

What do the inner cells and outer of the morula give rise to?

A

Inner: Embryoblast
Outer: Trophoblast

THINK ET (phone home)

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19
Q

How do trophoblasts bind between the epithelial cells of the uterine mucosa?

A

L-selctins on the trophoblastic cells attach to carbohydrate receptors on the uterine epithelium

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20
Q

At day 8, what two layers does the trophoblast differentiate into?

see notes for pic

A

Syncitiotrophoblast - this is the invading layer intto the wall of uterus. These are multinucleated.
Cytotrophoblast. These are mononucleated

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21
Q

At day 8, what two layers does the embryoblast differentiate into?

A

Hypoblast (closer to surface of endometrium)
Epiblast (closer to trophoblast cells)

Epiblast cells next to amniotic cavity are amnioblasts

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22
Q

What stage is it at 9 days?

see notes for pic

A

Lacunar stage

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23
Q

What closes up the area where the embryo originally penetrated the endometrium?

A

Fibrin coagulum

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24
Q

At the lacunar stage, vacuoles appear in the syncytium of syncitiotrophoblasts. They fuse to form what?

A

Lacunae

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25
The ring of hypoblast cells form what lining of the primitive yolk sac?
exocoleimic/Heuser membrane
26
New cells appear between the surface of the inner surface of the cytotrophoblasts and the outer surface of the exocoelomic cavity. What are they called?
the extraembryonic mesoderm |  Spaces form WITHIN this called extraembryonic cavities
27
When does gastrulation occur?
15-16 days
28
What mediates the movement of cells from the epiblast to then go on to form the trilaminar disc?
Fibroblast growth factor 8
29
Function of gastrulation?
• Create body axes o Anterior-posterior o Dorsal-ventral o Left-right
30
Layers of trilaminar disc from most inside to most outside (in realtion to implantation)
Ectoderm Mesoderm Endoderm
31
Endoderm derivatives
Endoderm---> lining of digestive and respiratory tracts, parts of liver, pancreas, thyroid and bladder;
32
Mesoderm derivatives
Mesoderm---> circulatory system, excretory system, muslces, connective tissue, organs.
33
Ectoderm derivatives
Ectoderm ---> Integument (everything you can see like skin), lens of the eye and nervous system;
34
What induces neurulation?
Upregulation of FGF Inhibition of BMP4 Wnt family of proteins Shh protein (Sonic) (bone morphogenetic protein 4 this is an example of a transforming growth factor-beta (TGF-beta)) o Sonic hedgehog protein (Shh) initially expressed in the notochord induces neural pattering as well as patterning the somites
35
3 types of spina bifida?
o Myelomeningocele  spinal canal remains open along several vertebrae in the back o Meningocele  Meninges push out through the spine; the spinal cord usually develops normally o Spina bifida occulata  One or more vertebrae don't form properly, but the gap in the spine is very small • No pain or neurological disorder • Common • Only sign may be a dimple or tuft of hair
36
What are the three principles of tetatogenesis?
Factors affecting teratogenesis (3 principles of teratogenesis) 1. Dosage 2. Time and length of exposure 3. Genotype of the embryo
37
Give an example of a chromosomal abnormality:
• Microdeletions in contiguous (close to each other) genes Regions of CGG repeats are fragile E.g. Fragile X syndrome • Low IQ, long and narrow face, large ears, flexible fingers, and large testicles
38
What percentage of human malformations are due to one defective gene?
8%
39
What happens to baby if mum bets rubella in 0-12 weeks
``` 100% risk of infection o Congenital rubella syndrome o Leading to cataracts o Cardiac defects o Spontaneous abortion in 20% of cases ```
40
What happens to baby if mum bets rubella in 12-16 weeks
Deafness and retinopathy
41
What happens to baby if mum bets rubella in 16+ weeks?
Normal | Slight risk of deafness/retinopathy
42
What can X-Rays cause to baby during pregnancy?
```  Microcephaly  Skull defects  Spina bifida  Blindness  Cleft palate  Limb defects ```
43
When is the embryo most susceptible to terattogens?
5 weeks is most susceptible Exponential increase up to 5 weeks, then continuous fall from then on
44
What is the BNF advice on pregnancy and drugs
and all drugs should be avoided if possible, during the first trimester If uou are going to use drugs, use tried and tested drugs and use the smallest dose
45
What did the use of thalidomide during pregnancy cause?
Phocomelia - a rare congenital deformity in which the hands or feet are attached close to the trunk, the limbs being grossly underdeveloped or absent
46
What is isotretinoin and what did it cause when taken during pregnancy?
``` Analogue of vitamin A used for acne treatment o If used during pregnancy  Abnormalities of • Eye • Ears • Skull • CNS • CVS ```
47
How does nicotine from smoking affect babies?
Nicotine is vasoconstrictor Less blood to placeneta Also crosess BBB and inhibits cell growth
48
Define gestational age
Time from woman's last period
49
Define embryological age
Time from conception
50
Role of hCG before implantation | Role of hCG after implantation
Maintain corpus luteum | Tell mother that egg has been implanted, so don't do myometrial contractions or endometrial shedding
51
After 6-8 weeks, what is the main producer of hCG?
The placenta
52
What is hPL and whats the other name?
Human placental lactogen. human chorionic somatomammotropin (hPL)
53
What secretes hPL and to where?
by syncitiotrophoblast cells, but unlike hCG, it is secreted into the maternal circulation
54
Function of hPL
 Proliferation of breast tissue  Stimulation of milk secretion  Adjust plasma levels of metabolites to help the foetus • E.g. reduces the sensitivity of maternal cells to insulin • Also inhibits gluconeogenesis so more amino acids in plasma • Increases lipolysis which increases free fatty acids in plasma o Thus counteracting the fall in metabolites in maternal circulation due to foetal uptake
55
3 types of chromosome?
Metacentric - centromere in the middle Submetacentric Acrocentric - far to one end
56
Genetic cause of cri du chat syndrome?
Deletion of short arm on chromosome 5: 46, XY, del(5p) OR 46, XX, del(5p) More common in girls 4:3 ratio o Feeding problems because of difficulty in swallowing and sucking; o Low birth weight and poor growth; o Severe cognitive, speech and motor disabilities; o Behavioural problems such as hyperactivity, aggression, outbursts and repetitive movements; o Unusual facial features, which may change over time; o Excessive drooling; o Small head (microcephaly) and jaw (micrognathism); o Widely-spaced eyes (hypertelorism); o Skin tags in front of eyes.
57
Why are the affects of sex chromosome abnormalities so mild?
X-chromosome inactivation o In female somatic cells, one X chromosome is randomly inactivated o There is a counting mechanism that counts the number of X’s and then ensures only one is active Thus don't make double proteins as men (who only have 1 X)
58
What is a reciprocal translocation
Equal amounts of chromosome break off and swap so no net gain or loss of genetic info
59
Robertsonian translocation explain"
Two acrocentric chromosomes join tohether to form one really long one. Two short bits join and this is lost.
60
Robertsonian translocations occur most between which chromosomes?
13,14,15,21 and 22 | Hence the link to Robertsonian Downs
61
# Fill in blank 1. Take blood in anticoagulant 2. Purify lymphocytes 3. Culture and encourage mitosis using ---------- 4. Disrupt mitotic spindles with ------ 5. Add to hypotonic solution so they swell to harvest cells 6. Fix cells to a microscope slide 7. This will show banding pattern
Phytohemagluttin | Colcemid
62
Genetic basis of Turner's syndrome?
``` Monosomy X (so only affects girls) 45,X ```
63
Symptoms fo Turner's?
Often, a short and webbed neck, low-set ears, low hairline at the back of the neck, short stature, and swollen hands and feet are seen at birth.[1] Typically, they develop menstrual periods and breasts only with hormone treatment, and are unable to have children without reproductive technology.[1] Heart defects, diabetes, and low thyroid hormone occur more frequently.[1] Most people with TS have normal intelligence.[1] Many have troubles with spatial visualization that may be needed for mathematics.[1] Vision and hearing problems occur more often.[5]
64
Genetic basis of Edward's syndrome?
Trisomy 18
65
Symptoms of Edward's?
``` o Microcephaly o prominent back portion of the head (occiput), o low-set, malformed ears o abnormally small jaw (micrognathia) o cleft lip/cleft palate o upturned nose o narrow eyelid folds (palpebral fissures) o widely spaced eyes (ocular hypertelorism) o drooping of the upper eyelids (ptosis) o a short breast bone o clenched hand o underdeveloped thumbs and/or nails o absent radius o webbing of the second and third toes o clubfoot or rocker bottom feet o Multiple joint contractures ```
66
Genetic basis of Patau's?
Trisomy 13
67
Symptoms of Patau's
``` o Polydactyly (extra digits) o Cyclopia o Proboscis o Low-set ears o Prominent heel o Deformed feet known as rocker-bottom feet o Cleft palate o Microcephaly o Brain doesn’t divide o Organs coming out of navel: Omphacele ```
68
Genetic basis of Klinefelter's Syndrome
Multiple X chromosomes Such as 47,XXY As there is a Y chromosome, they are male. ONLY affects males
69
Klinefelter's symptoms?
``` o 1-2 in 1000 o Primary hypogonadism (high FSH/LH but low testosterone) o Pubertal gynaecomastia o Small testes o Delayed onset of secondary sexual characteristics o Infertility o Treatment  Testosterone ```
70
Symptoms of XYY syndrome?
There are usually few symptoms.[2] These may include being taller than average, acne, and an increased risk of learning problems.[1][2] The person is generally otherwise normal, including normal fertility.[
71
Genetic basis of DiGeorge syndrome?
22q11.2 deletion
72
DiGeorge syndrome symptoms?
While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent infections, developmental delay, learning problems and cleft palate.
73
What is screened for in pregnancy?
``` • Early pregnancy o Estimate gestational age o Viability o Detect multiple pregnancies o Nuchal translucency • Fetal anomaly • Blood groups and antibodies • Hepatitis B • HIV • Sickle cell and thalassaemia • Down’s syndrome ```
74
When is a nuchal translucency test performed?
11-13 weeks
75
When is foetal anomaly scan performed?
18-20 weeks
76
↑ α-fetoprotein in amniotic fluid and maternal serum can be indicative of?
Neural tube defect (from notes) | But many other tumours also

Case 7 (1 decks)

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