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 rna from the nucleus to the ribosomes.

Explanation:

1. In genetics, it is groups of three nucleotides (codons), not four, that specify a particular amino - acid, 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. During gene expression, messenger RNA (mRNA) copies the genetic instructions from DNA in the nucleus and carries them to the ribosomes for protein synthesis. This statement is true.

Answer:

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