Chapter 4 – Nucleic acids

OBJECTIVE: Describe how information is transmitted from the nucleus to the cytoplasm, where it is used to make proteins.

The nucleic acid that resides in the nucleus is…
The nucleic acid that can travel through the nuclear envelope is …
Ribosomes are used for manufacturing proteins. In what part of the cell do they reside?

OBJECTIVE: Describe the structure and function of nucleotides and nucleic acids (DNA & RNA).
Draw the sugars deoxyribose and ribose. Number the carbon atoms and indicate the difference between them.
What are the 3 components of a nucleotide? Draw them conceptually.
To which carbon atom is the phosphate group attached?
To which carbon atom will the next nucleotide join? (This is very important)
Why do you think DNA is described as having 3 and 5 ends?
Draw a simple diagram to show what is meant by the term ‘antiparallel’ when referring to DNA.
A pyrimidine is always complementary to a …
Which bases pair with which?
How can you explain Chargaff’s rules with what we now know about DNA structure (you’ll need to read Chapter 16.1)?
How does the size of purines and pyrimidines indicate about the width of the DNA double helix?

Do the following in or after class…

Using the skills in “Tips on drawing Nucleic acids” (Making models 4.2), write a DNA sequence 5’-GGAGAACTTCCCC-3’. Notice that the first part of this sequence contains G and A, which are purines, whereas the second part of the sequence contains pyrimidines. Why does the width of the molecule NOT change from the first part to the second? Use a diagram to help you explain.
The genome of a particular organism contains 35% guanine. What proportion of the genome is adenine?
Based on its structure, why do you think RNA is so much more reactive than DNA?
Scientists sometimes find “ancient DNA” from organisms that died a long time ago (sometimes many thousands of years; think about Jurassic Park!). Why would they be unlikely to find ancient RNA?