Nucleic Acids

RNA vs DNA

Main differences:RNA DNA

Practice!

1. On a separate page, create your own symbols to represent the components of a nucleotide. Use these symbols to draw a simplified model of a double stranded DNA molecule.

2. Write the complementary DNA strand to the following nucleotide sequence

5’ – A G C C G A T T A C G C A A T G G A U G S S C A – 3’

3. On a separate page, write brief paragraphs to explain each of the following:

a) Why do cells need to use both DNA and RNA (i.e. discuss the location of each)? What signals can proteins in the nuclear membrane use to distinguish between the two?

b) Explain how DNA and RNA molecules have “directionality”. How does this relate to their structure? What does it mean to say that DNA strands are antiparallel?

c) In terms of 3D structure, fully explain why A only links to T and G only links to C. What would be the structural consequences if the purines A and G were linked?

d) The human genome is about 3 billion base pairs long stretching almost 2m end to end. Explain how this extremely long DNA sequence fits compactly in the nucleus of every single one of our over 10 trillion cells?

4. Copy and complete the summary table below into your notes. Use it to summarize the different types of nucleic acids studied in this course. DNA has already been filled out for you as an example.

Molecule

Function Main structural features

DNA “blueprint” for cells / organisms Genetic code

Deoxyribose sugar – phosphate backbone

A-T C-G Complimentary / antiparallel double helix 5’ 3’ phosphodiester bonds

mRNA

tRNA

rRNA

snRNA

ATP