Final answer:
Specific alleles in genes increase the chance of offspring with mental disorders. Recessive alleles can lead to genetic disorders if both parents are carriers. Inbreeding among carriers increases the likelihood of these disorders manifesting.
Step-by-step explanation:
Having specific types of alleles in genes increases the probability of having offspring with mental disorders. Genetic disorders, such as cystic fibrosis or Tay-Sachs disease, can be influenced by the inheritance of specific recessive alleles. If both parents are carriers of a recessive allele for a disorder, they can use a Punnett square to predict the likelihood of their offspring inheriting the disease. For X-linked disorders, males are more affected because they only need to inherit one copy of the recessive allele, whereas females would need two. Germline mutations in these alleles can increase susceptibility to the disorder. Furthermore, inbreeding within a family of carriers can significantly increase the chances of homozygous recessive offspring, leading to conditions such as inbreeding depression.