Heredity — Important Questions

Dominant traits are expressed even with one copy of the allele, Recessive traits need two copies of the allele to be expressed, A single gene can have both dominant and recessive alleles

Dominant traits are expressed when at least one dominant allele is present (TT or Tt). Recessive traits are only expressed when both alleles are recessive (tt). Dominant traits are not necessarily more common, and recessive traits are not necessarily harmful.

Males have XY chromosomes, Females have XX chromosomes, The Y chromosome is smaller than the X chromosome

In humans, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). The Y chromosome is much smaller than the X chromosome and carries fewer genes.

Father only

The father determines the sex of the child because mothers always contribute an X chromosome, while fathers can contribute either an X (resulting in a girl) or a Y chromosome (resulting in a boy).

All plants are tall

When a pure tall plant (TT) is crossed with a pure short plant (tt), all F1 offspring have the genotype Tt. Since T is dominant over t, all F1 plants are tall.