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Course: Science — Third Preparatory

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Science — Third Preparatory

Science — Third Preparatory

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Science — Third Preparatory 2026/2027

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Unit 1 - Force, Motion, Acceleration and Physical Quantities

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Text lesson

Unit 3 — Variation of Traits in Living Organisms

Science — Third Preparatory

Unit 3 — Variation of Traits in Living Organisms

1.10 Marriage between close relatives

1.10 Marriage between close relatives

Relatives share some genes they inherited from common ancestors.
If one of these genes causes a disease, the probability that both partners are carriers of the same disease allele is higher in relatives than in unrelated couples.
When both carry the same recessive allele, the chance of an affected child (1 in 4) increases.
For this reason health authorities recommend:

Comparison aspect	Main idea	Keywords
pre-marital medical screening	for certain inherited diseases	certaininheriteddiseases
genetic counselling	specialists study the family’s medical history run genetic tests and advise couples about the risks which protects families and reduces the spread of diseases	specialistsstudyfamilymedical
comprehensive genetic screening	modern techniques that examine thousands of genes at the same time helping early detection of rare diseases	moderntechniquesexaminethousands

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