Question 1

Can two blue-eyed parents have a brown-eyed child?

Accepted Answer

It is extremely rare (under 1%). Because blue eyes typically result from homozygous recessive alleles at the HERC2/OCA2 switch, both parents carry inactive alleles. Rare exceptions arise from modifier genes (SLC24A4, TYRP1) or de novo germline mutations.

Question 2

Why do many babies have blue eyes at birth that turn brown later?

Accepted Answer

Melanocytes in the iris stroma require light exposure after birth to stimulate melanin synthesis. Over the infant’s first 6 to 12 months, gradual eumelanin accumulation permanently shifts iris pigmentation.

Question 3

What genes determine human eye color?

Accepted Answer

Eye color is a complex polygenic trait. The primary driver is the OCA2-HERC2 locus on chromosome 15 (accounting for ~75% of eye color variance), modulated by GEY/SLC24A4 on chromosome 19, SLC45A2, and TYR.

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