What do Hindu scriptures say regarding people with genetic disorders marrying and reproducing?
People with diseases or any kind of severe genetic deformities should not be married.
Manu 3.8 - He should not marry a maiden with tawny hair, nor one with superfluous limbs, nor one who has disease, nor one who has either no hair or too much hair, nor one who is garrulous, nor one with reddish eyes.
Viṣṇu (24.12-16) Not one who is diseased or with excessive limbs; or with deficient limbs; nor one who is too pale, or too talkative.’
Yājñavalkya (1. 3).—‘One who is free from disease.’
Yama (Vīramitrodaya-Saṃskāra, p. 731).—‘Too short, too tall, too thin, too fat, with tawny eyes, too pale,—such girls should not he accepted.’
Viṣṇu-purāṇa (Vīramitrodaya-Saṃskāra, p. 731).—‘The wise man shall not marry a girl who hears signs of a beard, who has a masculine appearance, whose voice is cracked, who speaks insinuatingly, whose voice is like the crow’s, who looks on without, winking, whose eyes arc defective;—he shall not marry her whose thighs arc hairy, whose ankles are high, in whose, cheeks there are dimples;—he shall, not marry a girl whose skin is rough, who is pale, who is diseased, or with red eyes, or with lean hands and feet,—or one who is dwarfish, or too tall, or one whose eye-brows arc joined: nor one whose teeth have many holes, nor one with a frightful face.’
This rule applies even to women:
Manu 9.88 - One shall give his daughter in the proper form, even though she may not have attained (the age), to a bridegroom who is of exceptionally distinguished appearance, and her equal.
Śātātapa (Do., p. 755).—‘That bridegroom should be selected who is seeking for a wife and is endowed with good family and character, handsome, learned, intelligent and young, and free from defects.’
Yama (Vīramitrodaya-Saṃskāra, p. 754).—‘Family, character, beautiful body, age, learning, wealth, presence of guardians,—these seven qualifications should be sought for before a girl is given away; nothing else need be considered.’
Lalla (Do.).—‘Caste, learning, age, character, health, large family, wealth, Brahmanic character,—these eight should he the qualities of the Bridegroom.’
All these qualities indicate severe health problems.