Question

Ruby's father has curly hair and her mother has straight hair. Ruby, however, has wavy hair. What could be the reason for this?

Answer 1

Have you talked about CODOMINANCE, in class?

CODOMINANCE is where a certain trait (like hair type)
has MORE THAN ONE dominant allele.

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You know what alleles are, right?
They're letters that you can put together, to make a genotype.

And you know that a genotype is a group of letters, that determines a trait.

For example....(T T), (T t), (A a)....

Now, when you talked about genotype, in class,
you probably learned that in a genotype, the capital letter matters more than the lowercase letter.

For example,

If Capital T is TALL
and lowercase t is SHORT...

then the genotype (T t) would mean that the organism is TALL.
The genotype (T T) would also mean that the organism is TALL.

but the genotype (t t) would mean that the organism is SHORT.

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Now, in CODOMINANCE,
a trait can have MORE THAN ONE capital letter.

And if BOTH capital letters are in the genotype,
then BOTH capital letters matter.

For example,
blood type is a trait.

There are three alleles for blood type : A B i

A and B are both DOMINANT alleles.

And if your genotype is (A B)
then BOTH letters will matter.
And your blood type would be AB.

Do you get that?

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Now, the trait in the question is hair type.

The father has CURLY hair.
The mother has STRAIGHT hair.
The child has WAVY hair.

Can you see how...
if you add CURLY HAIR + STRAIGHT HAIR....
you can get WAVY HAIR?

What that means is that the genes for STRAIGHT hair and CURLY hair are both DOMINANT.

And that hair type is a CODOMINANT trait.