Question

select the true statements. within a gene, each group of four nucleotides specifies a particular amino acid. there are only three different types of dna nucleotides. each species uses its own genetic code. copies of the genetic instructions for proteins are carried by molecules of mrna from the nucleus to the ribosomes.

Explanation:

1. In reality, within a gene, each group of three nucleotides (a codon) specifies a particular amino - acid, not four. So the first statement is false.
2. There are four different types of DNA nucleotides (adenine - A, thymine - T, guanine - G, cytosine - C), not three. So the second statement is false.
3. The genetic code is nearly universal across species, not unique to each species. So the third statement is false.
4. Messenger RNA (mRNA) carries copies of the genetic instructions for proteins from the nucleus to the ribosomes. This is a correct biological process.

Answer:

Copies of the genetic instructions for proteins are carried by molecules of mRNA from the nucleus to the ribosomes.