A1.2 Nucleic Acids (HL)

A1.2.11 Describe how the structure of DNA dictates directionality

• nucleotides linked in the same way

• pentose sugar unlinked = C3 exposed, phosphate unlinked = 5 terminal

• 5’ to 3’ terminal

List the molecules that are influenced by directionality

Polymers or ribosomes

Outline the directionality of replication

• DNA nucleotides added to 3’ end of polymer

• 5’ phosphate linked to 3’ sugar

• Both strands templates (5-3)

Outline the directionality of transcription

• RNA nucleotides added to 3’ end

• 5’ phosphate to 3’ sugar

• Both strands templates (5-3)

Outline the directionality of translation

• Ribosomes go 5 to 3 end on MRNA

• Read codons and link amino acids

A1.2.12 Compare purines and pyrimidines and describe how they contribute to DNA stability

• A+G Purines: two rings

• T + C Pyrimidines: one ring

• Each base pair has one purine and one pyrimidines

• Helps made DNA stable and allows any sequence of bases in genes of DNA

A1.2.13 Outline the structure of a nucleosome

• Present in Eukaryotes only

• DNA wrapped twice around Histone

• Extra H1 reinforces binding of DNA to nucleosome and packages proteins

• 8 Histone proteins