HEREDITY
BACKCROSS OR TESTCROSS
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
a mutation occured before the child was born
|
|
|
both parents carry the allele for blue eyes
|
|
|
both parents are pure for brown eyes
|
Detailed explanation-1: -For two parents with brown eyes to have a blue-eyed child, both parents must genetically be Bb. When this happens, there is a 1 in 4 chance that these parents will have a bb child with blue eyes. Unfortunately, eye color is not as simple as this.
Detailed explanation-2: -Likewise, two brown-eyed parents can have a child with blue eyes, although this is also uncommon.
Detailed explanation-3: -If one parent has brown eyes and one has blue, the child could have either one. If the parent with brown eyes has brown-eyed parents, the child will likely have brown. However, if the parent with brown eyes has a blue-eyed parent, you could have a blue-eyed baby.
Detailed explanation-4: -If both of you have brown eyes, then there is generally a 25% chance that the baby will have blue eyes if both of you carry the recessive blue-eye gene. But if only one of you has a recessive blue-eye gene, and the other has two brown, dominant genes, then there is a less than 1% chance of the baby having blue eyes.