Chapter 4 Chapter 4

Nucleic AcidsNucleic Acids

““The Flow of Genetic The Flow of Genetic Information in the Cell” Information in the Cell”

Nucleic AcidsNucleic Acids

Polymers specialized for the storage, Polymers specialized for the storage, transmission, and use of genetic transmission, and use of genetic information.information.

DNADNA = deoxyribonucleic acid = deoxyribonucleic acid

RNARNA = ribonucleic acid = ribonucleic acid

The monomeric units (building blocks The monomeric units (building blocks of nucleic acids) are of nucleic acids) are nucleotidesnucleotides..

NucleotidesNucleotides

Consist of a Consist of a pentose sugarpentose sugar, a , a phosphate groupphosphate group, , and a and a nitrogen-nitrogen-containing basecontaining base..

Nitrogenous BasesNitrogenous Bases

DNA bases: adenine (A), DNA bases: adenine (A), cytosine (C), guanine (G), cytosine (C), guanine (G), and thymine (T)and thymine (T)

Complementary base Complementary base pairing:pairing:

A–T(U)A–T(U)

C–GC–G

Purines pair with Purines pair with pyrimidines by hydrogen pyrimidines by hydrogen bonding.bonding.

Instead of thymine, RNA Instead of thymine, RNA uses the base uracil (U).uses the base uracil (U).

Nucleic Acid SynthesisNucleic Acid Synthesis

The “backbone” of DNA The “backbone” of DNA and RNA is a chain of and RNA is a chain of sugars and phosphate sugars and phosphate groups, bonded by groups, bonded by phosphodiester linkagesphosphodiester linkages..

Nucleic Acid SynthesisNucleic Acid Synthesis

• The two strands of The two strands of DNA run in opposite DNA run in opposite directions directions ((antiparallelantiparallel).).

RNA vs. DNARNA vs. DNA

DNADNA

The two strands of a DNA molecule The two strands of a DNA molecule form a double helix. (anti-parallel)form a double helix. (anti-parallel)

All DNA molecules have the same All DNA molecules have the same structure; diversity lies in the structure; diversity lies in the sequence of base pairs.sequence of base pairs.

RNARNA

Single StrandedSingle Stranded

Less Stable then DNALess Stable then DNA

What clue does this What clue does this give us to its function give us to its function in comparison to in comparison to DNA?DNA?

““The Correct Flow of Genetic The Correct Flow of Genetic Information in the Cell”Information in the Cell”

The complete set of The complete set of DNA in a living DNA in a living organism is called its organism is called its genomegenome..

Not all the information is Not all the information is needed at all times; needed at all times; sequences of DNA that sequences of DNA that encode specific proteins encode specific proteins are called are called genesgenes..

Central Dogma of Molecular Biology