Question

A couple's children have curly hair and brown eyes. Both parents have brown eyes (BB) but one has curly hair (Cc) and the other has straight hair (cc). What is the probability (#with trait/total #types of traits) that the next child will have brown eyes and straight hair? (do a Punnett square)

O 1/16
O 1/8
O 1/4
O 1/2
O 1

Answer 1

The probability of the next child having brown eyes and straight hair is 1/2 or 50%, determined by a Punnett square analyzing the curly/straight hair trait since the brown eye trait is already homozygous dominant.

Step-by-step explanation:

The probability of the couple's next child having brown eyes and straight hair can be determined using a Punnett square. Since both parents have brown eyes with genotypes BB (one from each parent), the child will definitely have brown eyes because BB is homozygous dominant. However, for hair type, one parent is heterozygous curly (Cc) and the other is homozygous straight (cc). So, we set up a Punnett square for hair type:

• Top of the square: Cc (from the curly-haired parent)
• Side of the square: cc (from the straight-haired parent)

Crossing these, we get:

• Box 1: Cc (Curly)
• Box 2: Cc (Curly)
• Box 3: cc (Straight)
• Box 4: cc (Straight)

Out of the four possibilities, two show that the child will have straight hair. Therefore, the probability of having brown eyes (which is certain) and straight hair is 2 out of 4, which simplifies to 1/2 or 50%.