When a child is born with down syndrome, when did the mutation occur?

All individuals have two alleles for a given trait. according to mendel's these alleles are passed down one each from both mother and father.

How does photosynthesis show the conservation of mass and energy?

Read the article and use the information to answer the questions that follow discovering the structure of dna explain how the discoveries by rosalind franklin watson and crick build an accurate model of dna done