nucleic acids

role of DNA and RNA in cells

• nucleic acids

  • macromolecules made out of units called nucleotides

  • come in two naturally occurring varieties: DNA and RNA

• deoxyribonucleic acid (DNA)

  • the genetic material found in living organisms

• ribonucleic acid (RNA)

  • the genetic material that is used by some viruses

DNA in cells

• eukaryotes

  • DNA is found in a nucleus

  • DNA is typically broken up into long, linear pieces called chromosomes

• prokaryotes

  • DNA is found in a specialized cell region called the nucleoid

  • DNA is broken up into smaller and often ring-shaped chromosomes

from DNA to RNA to proteins

• messeger RNA (mRNA)

  • an RNA copy (transcript) of a gene

  • serves as a messenger between DNA and ribosomes

  • sequences read by molecular machines and used to build proteins

• central dogma

  • the progression from DNA to RNA to protein

nitrogenous bases

• DNA

  • adenine (A)

  • guanine (G)

  • cytosine (C)

  • thymine (T)

• purines

  • structures that have two fused carbon-nitrogen rings

    • ex: adenine and guanine

• pyrimidines

  • structures that have a single carbon-nitrogen ring

    • ex: cytosine and thymine/uracil

• RNA

  • adenine (A)

  • guanine (G)

  • cytosine (C)

  • uracil (U)

polynucleotide chains

• directionality

  • two ends that are different from each other

• 5’ end

  • beginning of the chain

  • the 5’ phosphate group of the first nucleotide in the chain sticks out

• 3’ end

  • the 3’ hydroxyl of the last nucleotide added to the chain is exposed

• DNA sequences are usually written in the 5’ to 3’ direction

  • the nucleotide at the 5’ end comes first

  • the nucleotide at the 3’ end comes last