Match the following regulatory elements and eukaryotes with their definitions

1. dermis

2. chemical

3. urine

4. viruses

5. antibodies

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.