(8/27/10) - DNA Fundamentals

1. Describe the functions of nucleic acids in the cell.

Storage of information in nucleotide sequence, selectively utilize stored information, reproduce stored information precisely, and catalysis (RNA)

2. Describe how information is encoded in DNA.

The linear order of the nucleotide bases in a 5’-3’ direction encodes genetic information.

3. Describe the different ways information encoded in DNA is transformed into functional units in the cell.

DNA can be read to produce mRNA for protein synthesis, tRNA for shuttling of amino acids, rRNA for parts of a protein synthesis complex, snRNA for splicing and regulation, or miRNA for (usually) gene silencing

4. Describe the three chemical groups that make up each DNA unit and explain how they contribute to the function of DNA.

Nitrogenous bases--linear order of bases attached to phosphate/sugar backbone encodes genes

Sugars--deoxyribose or ribose; bases are anchored at the anomeric carbon of sugar

Phosphates--phosphates link sugars together in a 5’-3’ phosphodiester linkage

5. Describe what chemical differences delineate RNA from DNA.

DNA’s sugar is deoxyribose instead of ribose. This makes for a more stable (less hydrolysable) strand; DNA uses thymine and RNA uses uracil

6. Detail how the chemical differences between DNA and RNA contribute to their differing functions in the cell.

DNA, being complementary double stranded and more stable makes it suitable for long-term storage of genetic information; double-stranded allows for replication and repair. RNA, being single stranded, is suited for reading/processing/folding to produce functional units.

7. Describe what it means for DNA to be antiparallel and complimentary.

Antiparallel--DNA strands are opposite one-another chemically (one is 5’-3’ and other is 3’-5’)

Complimentary--strands pair with each other at the nitrogen bases AT, GC.

8. Define two types of forces involved in DNA structure and their individual contributions.

Hydrophobic stacking interactions (polar exclusion) and base-pair hydrogen bonding

9. Describe the functions of the major and minor grooves of DNA.

They are places on the DNA structure where individual base pairs are identifiable; as such, they are the association points with proteins

10. Describe how proteins access the information stored in DNA sequences.

Proteins have structures that “read” bases in major and minor grooves

11. Describe how DNA is packaged in the cell nucleus and what the consequences are of this packaging.

DNA is wrapped around histones to form nucleosomes, which are the units that comprise chromatin. This packing prevents protein access to the DNA--DNA needs to be unpacked and unwound to transcribe anything.

12. List the instances where DNA is linear or circular.

Regions of a linear DNA chromosome can behave as though it is circular because of interactions between chromosomes and proteins.