How many mutations have you counted? And how did you judge them to be positive or negative?
According to the following excerpted information on Human Genetic Diseases there are at least 400-500 genetic diseases that can be diagnosed prenatally. I don't know how many more human genetic diseases have been diagnosed postnatally.
Now compare that to the number of positive Human Genetic Mutations known to exist. The only ones I can think of that could be considered to be positive would be 1) having 6 digits compared to 5, and 2) Gigantism - but that is associated with an early death as the heart tends to give out.
HUMAN GENETIC DISEASES
http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookhumgen.html
One in every 200 newborns has a recognizable chromosomal abnormality. It is estimated that as many as 70% of fertilized eggs are abnormal, and most are spontaneously aborted. Most genetic disorders are traced to an allele for a recessive trait that codes for an ineffective or nonfunctional protein product. Humans possess 50-100,000 human genes.
DOWN SYNDROME: nondisjunction of the 21st chromosome (Trisomy 21). 1 out of 600 births, 1 in 1500 for women under 30, 1 out of 80 for women 40-45 years old.
CYSTIC FIBROSIS: caused by a recessive autosomal gene (#7). Affects the exocrine glands: mucus, sweat, tears, saliva. Mucous is abnormally thick and gluey. Instead of keeping the breathing tubes free of dust and dirt, it makes breathing more difficult, clogging the air passages. Trapped germs lead to respiratory infections. Sweat is extremely salty. 1 in 20 people carry at least one gene for CF. Mainly affects Caucasians, and is the most common genetic disease in this population.
SICKLE CELL ANEMIA: a recessive autosomal gene (#11) that provides protection against malaria. In some parts of Africa the gene is in 40% of the population. Is also found in Middle Eastern and Mediterranean countries. In the USA the trait can be found in 10% of blacks. About 1 in 625 newborn blacks have sickle cell anemia. One in 10 American Blacks carry the gene for the trait.
PHENYLKETONURIA (PKU): caused by a recessive autosomal gene (#12). Affected individuals excrete phenylpyruvic acid in their urine. A sister of JFK had this condition and was mentally retarded.
HUNTINGTON'S DISEASE: caused by a dominant autosomal gene (#4) which does not manifest itself until adulthood. Results in irritability, indifference, poor judgement, forgetfulness and carelessness. Each offspring has a 50% chance of getting the disease.
TAY-SACHS DISEASE: a recessive autosomal mutant gene (#15) with 85% of the cases found in Eastern European Jews. Results in death by age 4-5. 1 out of every 25 Jews of Eastern European origin carries the gene. 82% of the babies born with Tay-Sachs disease are born into family with no prior history of the illness.
DUCHENNE MUSCULAR DYSTROPHY: deletion on the X chromosome causing a frame shift recessive mutation. The muscles are replaced by fatty tissue.
MYOTONIC DYSTROPHY: caused by a dominant mutant gene on chromosome #19. Fingers can't relax.
GLUCOSE-6-PHOSPHATE DEHYDROGENASE (G6PD) DEFICIENCY: the most common human enzyme deficiency in the world affecting an estimated 400 million people. It is caused by an X-linked recessive gene and causes hemolytic anemia. G6PD deficient individuals are resistant to the malaria causing parasite. The anemia iscaused by certain oxidative drugs because G6PD deficiency keeps affected red blood cells from being able to regenerate reduced NADPH. There are over 400 variant alleles, or different forms of the same gene. Most affected individuals reside in Africa, the Middle East and Southeast Asis. It can be found in as many as one in four among certain populations
HEMOPHILIA: caused by a recessive X-linked gene. Bruises and other internal bleeding cause the biggest problem; especially in the joints. Severe pain often occurs. Only 60 known cases of female hemophiliacs exist. 40% of women carriers result from spontaneous mutations with no family history of the disease.
MULTIFACTORIAL DISORDERS: arise from at least several genes interacting with the environment. 1. Heart Disease 2. High Cholesterol 3. Cleft Lip 4. Cleft Palate
DIAGNOSIS OF GENETIC DISEASES: a variety of techniques are used on fetuses and approximately 400-500 genetic disorders can currently be diagnosed prenatally.