Here's why:
* Heterozygous: This means the organism has two different alleles (versions) of the gene.
* Harmful trait: This means one of the alleles causes a disease or disorder.
* Carrier: The organism carries the harmful allele but doesn't necessarily show the symptoms of the disease. This is because the other allele is typically dominant and masks the effect of the harmful recessive allele.
Example:
* Cystic Fibrosis: A person with cystic fibrosis has two copies of the recessive cystic fibrosis allele.
* Carrier: A person who carries one copy of the cystic fibrosis allele and one copy of the normal allele is a carrier. They do not have cystic fibrosis, but they can pass the allele on to their children.
It's important to remember that while carriers may not experience the disease themselves, they can still pass the harmful allele to their offspring. This is why genetic counseling is important for couples with a family history of genetic disorders.
