2.6: Structure of DNA and RNA

prior learning & retrieval practice

U1: The nucleic acids DNA and RNA are polymers of nucleotides.

Exercise 1: Fill in the blanks

Nucleotides are the subunits that                                                     strands are built from, in the same way that starch or glycogen are built from                                      subunits. Polynucleotide strands are used to form nucleic acids:                and              . 

DNA Nucleotides are formed by joining a                           group and a                                    base to a                              sugar.  This is a 5 carbon (pentose) sugar and the phosphate and nitrogenous bases are joined to opposite ends of this molecule via                                                                               reactions.

U3: DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.

S1: Drawing simple diagrams of the structure of single nucleotides and of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases.

Exercise 2: Draw and label simple diagrams of single nucleotides and DNA and RNA.

Guidance from the guide: In diagrams of DNA structure, the helical shape does not need to be shown, but the two strands should be shown antiparallel. Adenine should be shown paired with thymine and guanine with cytosine, but the relative lengths of the purine and pyrimidine bases do not need to be recalled, nor the numbers of hydrogen bonds between the base pairs.

U2: DNA differs from RNA in the number of strands present, the base composition and the type of pentose.

Exercise 3: Compare and contrast DNA and RNA

Exercise 5: Outline how the structure of DNA allows for the efficient storage of genetic information