Topic 4---A: DNA,RNA and Protein Synthesis- 1. DNA

Question 1

Eukaryotic cells (DNA)

Answer 1

• Contain linear DNA molecules that exist as chromosomes that are each made up of one long molecule of DNA
• chromosomes are found in the nucleus
• The DNA molecule is really long so it has to be wound around histones so it can fit in the nucleus
• DNA and histone protein is coiled up very tightly to make a compact chromosome

Question 2

Prokaryotic cells (DNA)

Answer 2

• Also carry DNA as chromosomes
• DNA molecules are shorter and circular
• DNA isn’t wound around histones instead it condenses to fit in the cell by supercoiling
• located in the cytoplasm

Question 3

How does DNA loop around histones?

Answer 3

DNA helix within a chromosome winds around proteins called histones
This DNA protein complex is then coiled, looped and coiled again and condensed into a single chromosome