Question

This pedigree shows the inheritance Leber congenital amaurosis (LCA)
which is a type of hereditary blindness. Individuals with this disease lose
their vision during childhood.
3. What is the inheritance pattern shown?
4. Highlight one individual whose genotype is unknown. What additional
information would you need to determine his/her genotype?

Answer 1

I can't see the pedigree you mention — please upload it if you want comments tied to specific numbered individuals. Based on the usual features of LCA pedigrees, though, here are the answers you can use.

3) Inheritance pattern
- Autosomal recessive.
- Reason: affected children arise from unaffected parents (parents are carriers), both sexes are affected, and the trait can “skip” generations.

4) One individual with unknown genotype and what you would need
- Example: an unaffected sibling of an affected person (for instance “II‑2” if your pedigree labels generations) — this person could be either homozygous normal (AA) or a heterozygous carrier (Aa).
- What you would need to determine the genotype:
- Direct molecular (DNA) testing for the known disease-causing variant(s) in the family, or
- Clear genotypes of the parents (if both parents are confirmed carriers, the probability that an unaffected sibling is a carrier is 2/3), or
- Information about that individual’s offspring: if the person has an affected child, they must be a carrier; if all children are unaffected and the other parent is not a known carrier, that is weaker evidence but could change the likelihood.

If you upload the pedigree image I’ll point to a specific individual by pedigree label and calculate carrier probabilities.