Question

Gregor Mendel discovered some alleles can cover up the presence of others; these alleles are called __________.

Answer 1

Take a look at this genotype example:

(T t)

Pretend that Capital T stands for "Tall,"
and lowercase "t" stands for "short."

If a plant has that genotype,
then it would be TALL.

Why?
Because in a genotype, the CAPITAL letters matter more than the lowercase letters.

CAPITAL letters are DOMINANT alleles.
LOWERCASE letters are RECESSIVE alleles.

Whenever there is a CAPITAL letter (dominant alleles)
the LOWERCASE letter (recessive allele) gets blocked out.

Answer 2

DO you have any options?

Answer 3

We don't need multiple choices, really.
It's pretty straightforward.