DNA & Chromosome structure

Question 1

What is the role of DNA?

Answer 1

• Store genetic information

- Carries and allows genetic information to be passed on from parents to offspring

Question 2

Difference between DNA in prokaryotic cells and eukaryotic cells

Answer 2

Prokaryotic cells contain a single circular chromosome which is condensed in the nucleoid, found in the cytoplasm

In eukaryotic cells, linear DNA and proteins make up chromatin/chromosomes that is found in the nucleus

Question 3

What is purines and pyrimidines?

Answer 3

Purines:

• adenine
• cytosine

Pyrimidines:

• thymine
• guanine

Question 4

How does the structure of DNA contribute to its role?

Answer 4

DNA is double-stranded

• each strand is used as a template for copying during DNA replication
• DNA polymerase synthesizes the new DNA strand by adding complementary nucleotides

Stacked bases attract one another by hydrophobic interactions

• hydrophilic sugar-phosphate backbone interact with water molecules in an aqueous environment
• the shielding of bases by the sugar-phosphate backbone, resulting in the formation of DNA double helix
• this results in increased protection of genetic information from exogenous agent

Question 5

Role of histone proteins

Answer 5

• Histone proteins bind to DNA via charge-charge interaction
• Positive charges on histone proteins bind and neutralize the negative charge of the phosphate group of the DNA backbone
• This reduces repulsive forces between the same charges on the DNA molecule

Question 6

Hierarchy of organization in DNA

Answer 6

1. DNA double helix
2. Nucleosome
3. Solenoid
4. Chromatin fiber
5. Looped domains
6. Metaphase chromatin

Question 7

How can DNA be packed in prokaryotic cells?

Answer 7

• Most prokaryotic cells do not have histones

- They condense their DNA in the nucleoid through supercoiling

Question 8

What is the difference between DNA and RNA?

Answer 8

• Stability
• Basic subunits
• Composition of nucleotides
• Structural difference