Q32 (a)

Criteria	Marks
• Identifies similarities and differences in forms of DNA in bacteria and plant cells.	2
• Identifies a similarity or difference, OR identifies properties of DNA structure beyond the double-stranded helix.	1

Additional guidance from the source:

Bacterial DNA, bacterial plasmid DNA, plant chloroplast and plant mitochondrial DNA are circular. Bacterial and plant DNA are packaged with proteins. Differences: Most plant DNA is found as linear chromosomes, located in nucleus. Most bacterial DNA is found as a circular chromosome, with no nucleus. Range: 0-2; Average: 0.7 Comments: Compare mean similarities and differences. Many students only provided differences. A number of students identified properties, but did not make it clear what the similarities and/or differences were i.e. gave one type of property for one and a different type of property for the other. A number of students did not have a clear idea of what form of DNA meant, or did not have a clear idea of the form of DNA in plant cells and/or bacterial cells. Some common misconceptions or poorly explained concepts included that DNA was single stranded in bacteria, or in plasmids (it is generally double stranded), the plasmid was the main component of DNA in bacteria, bacterial DNA was not packaged with protein, there is nuclear DNA in bacteria, the main bacterial chromosome is linear.