This pertains to the structure of proteins. Secondary structures are stabilized by the presence of hydrogen bonds. The common types of secondary structures of proteins are the alpha helix and the beta sheets, each performing different functions.
Primary structure of protein is the peptide molecule comprised of peptide bonds. Once these peptide grows long enough, it will either be arranged into alpha helices or beta sheets stabilized by hydrogen bonds and this is the secondary structure. Once there is protein folding involved in the secondary structure of protein, then the folded protein is called the tertiary structure (or a protein subunit). When protein subunits come together to perform a specific function, then that is the quaternary structure.
Attached is a figure concerning the protein structures.
DNA synthesis occurs during the S phase, between the G1 and G2 phases of interphase. DNA replication is therefore complete before the mitotic phase begins.
Answer:
The correct answer would be 10.
The cell cycle can be divided into four phases namely gap 1 (G₁) phase , synthesis (S) phase, gap 2 (G₂) phase, and mitosis (M) phase.
DNA (deoxyribonuceic acid) content is only replicated and doubled in the S phase. However, the chromosome number remains the same. It can be explained as the number of chromosomes remains the same (2n) but number of chromatids doubles (4n) after S phase.
The number of chromatids restores to 2n in daughter cells after completion of mitosis.
Hence, if number of chromatids in metaphase was 20 i.e. 4n then the number of chromosomes (2n) would be 10.
Hence, 10 chromosomes or 5 pairs of chromosome would be present in the cell during its G₁ phase.