Question

Imagine that you are a doctor in a maternity ward. During your last shift, 20 babies were born. 10 had blue eyes, and 10 had brown eyes. Remember genotypes are the two alleles given for each trait, written with a letter. For this activity B =brown eyes b= blue eyes. Phenotypes are the physical appearance of the trait.
Given the phenotypes, what are the possible genotypes for these babies?

Answer 1

Answer: The possible genotypes include BB, Bb, and bb.

Explanation:

The brown eyes babies will have two possible genotypes: BB and Bb. BB has two genes for brown eyes while Bb has one gene for brown eyes and one gene for blue eyes. The gene for brown eyes B is a dominant gene while the gene for blue eyes b is a recessive gene. A dominant gene is a gene that has the ability to express itself phenotypically in the presence of a recessive gene. So the alleles BB and Bb will manifest as brown eyes outwardly. Blue eyes babies will have bb genotype. The allele is made up of two recessive genes. A recessive gene is a gene that cannot express itself in the presence of a dominant gene.

Answer 2

Answer:

Bb, BB, bb

Explanation:

Based on the information given by the question, there seems to be a 50% chance for there to be a baby born with blue eyes or brown eyes. Because B (brown eyes) is the dominant allele and b (blue eyes) recessive, You know that if a child is to have brown eyes, they will either will have the genotype BB or Bb, and if the child is to have blue eyes, it will have the sequence bb.

Extra Point:

The only way to give a 50% chance of a child having blue or brown eyes, as shown by the 10 babies with brown eyes and the 10 with blue, the parents must have a sequences of:

                    B                          b

              b    Bb                      bb

              b    Bb                      bb

• I can't make a Punnet Square using this application, but I hope that you see that one parent must have the Bb genotype, and one the bb to give the 50% chance of a child having blue or brown eyes.

Of course, not all parents will have this sequence, but for the purposes of study I wanted to show this. Also I'm sorry for any confusion you have with my answer, I haven't done biology in a long time, so this is based on bits and pieces of what I learned.