Congenital Malformations & Teratology

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  • Created by: Becca
  • Created on: 22-12-13 18:15
Define 'congenital malformation'.
Anatomical or structural abnormality present at birth
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Give examples of congenital malformations.
Cleft lip (mainly male), cleft palate (mainly female), omphalocoele (gut/umbilical hernia), septal defect, spina bifida etc.
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What numerical genetic factors cause congenital malformations?
(Numerical genetic factor = non-disjunction of chromosomes). Monosomy e.g. Turner syndrome. Autosomal trisomy e.g. Down syndrome (chromosome 21). Sex chromosome trisomy e.g. XXX, XXY, XYY. Tetrasomy & Pentasomy (usually lethal unless X chromosome)
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What is a structural genetic change & what causes them?
An inversion or translocation, often caused by radiation, viruses or drugs
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Define 'teratogenesis'.
A process where an abnormality is induced in a developing organism during uterine life by foreign agents called teratogens.
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What conditions must be met for teratogenesis to be induced?
The teratogen must get into contact with the developing embryo & the timing must be during the phase where the organ systems are being formed, the critical phase is the first 3 months following conception
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Describe embryotoxicity.
A direct toxic effect on the cells of the embryo. May also be toxic to the mother but embryonic cells are more sensitive. Result is lethal or results in reduction in growth.
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Describe the effect of teratogenesis on the pre-embryo.
"All or none effects". Agent kills the zygote if lethal dose or agent has no apparent effect if sublethal dose (minor injury can be completely repaired). This stage of embryogenesis is called the pre-differentiation stage.
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When is the embryonic stage? Why is this significant?
The first 14 weeks of pregnancy (first trimester). It signals the beginning of organogenesis , it is the period where the embryo is most vulnerable to a teratogenic assault. During this time, major morphological changes may occur.
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Give examples of drugs that cause congenital malformations & the conditions they cause.
Alcohol: fetal alcohol syndrome (mid-line facial abnormalities, behavioural effects). Antibiotics: tetracycline (effects teeth). Anticonvulsants: neural tube defects. Thalidomide: limb defects (amelia, meromelia, micromelia)
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What else can cause congenital malformations?
Infectious agents e.g. rubella (cataracts, cardiac defects, deafness) & syphilis (stillbirth, miscarriage). Environmental factors e.g. radiation (affects CNS), x-rays, pesticides, pollutants etc.
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What are the six general principles of teratology?
1) Result in death/malformation/growth retardation/functional disorder 2) Varies with point in developmental stage 3) Act in specific ways 4) No-effect to the totally lethal level as dosage increases 5/6) Depends on nature of agent & genotype
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Give examples of substances which a pregnant woman will be exposed to.
Drugs used prior to knowledge of pregnancy/necessary for disease independent of pregnancy e.g. anti-epileptics/necessary due to pregnancy specific disease. Environmental agents unnecessary but impossible to avoid e.g. crop sprays
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Other cards in this set

Card 2

Front

Give examples of congenital malformations.

Back

Cleft lip (mainly male), cleft palate (mainly female), omphalocoele (gut/umbilical hernia), septal defect, spina bifida etc.

Card 3

Front

What numerical genetic factors cause congenital malformations?

Back

Preview of the front of card 3

Card 4

Front

What is a structural genetic change & what causes them?

Back

Preview of the front of card 4

Card 5

Front

Define 'teratogenesis'.

Back

Preview of the front of card 5
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