Nucleotides and nucleosides

Nucleic acids

Unbranched polymers composed of repeating monomers called nucleotides

DNA

Stores genetic information and transmits it between generations

RNA

Translates DNA’s genetic information into proteins

Nucleotide

Composed of a monosaccharide, nitrogen-containing base, and phosphate group

Gene

Portion of DNA responsible for synthesis of a single protein

D-ribose

Aldopentose sugar in RNA

D-2-deoxyribose

Aldopentose sugar in DNA

Pyrimidine bases

Cytosine (C), uracil (U), thymine (T)

Purine bases

Adenine (A), guanine (G)

DNA bases

A, G, C, T

RNA bases

A, G, C, U

Nucleoside

Formed by joining the anomeric carbon of the sugar with a nitrogen atom of the base

Pyrimidine nucleoside naming

Use suffix “-idine”

Purine nucleoside naming

Use suffix “-osine”

Deoxyribonucleoside naming

Add prefix “deoxy-”

CMP

Cytidine 5'-monophosphate (ribonucleotide)

dAMP

Deoxyadenosine 5'-monophosphate (deoxyribonucleotide)

ADP

Adenosine 5'-diphosphate

ATP

Adenosine 5'-triphosphate

Phosphodiester linkage

Joins 3'-OH of one nucleotide to 5'-phosphate of another

Polynucleotide backbone

Alternating sugar and phosphate groups

DNA strand ends

5' end has phosphate; 3' end has OH

DNA double helix

Two strands run in opposite directions; bases inside, sugar-phosphate outside

Base pairing

A-T (2 hydrogen bonds), C-G (3 hydrogen bonds)

Replication

DNA makes a copy of itself

Transcription

RNA synthesized from DNA

Translation

Proteins synthesized from RNA

rRNA

Site of polypeptide assembly

mRNA

Carries DNA info to ribosome

tRNA

Brings amino acids; has anticodon and acceptor stem

Codon

Triplet of nucleotides coding for an amino acid

AUG

Start codon; codes for methionine

Stop codons

UAA, UAG, UGA

Mutation

Change in DNA sequence

Point mutation

Substitution of one nucleotide

Deletion mutation

Loss of nucleotides

Insertion mutation

Addition of nucleotides

Silent mutation

No change in amino acid

Sickle cell anemia

Caused by one amino acid substitution

Genetic disease

Mutation passed through generations

Recombinant DNA

Synthetic DNA with segments from multiple sources

PCR

Polymerase chain reaction; amplifies DNA

DNA fingerprinting

Uses PCR + restriction enzymes + gel electrophoresis

Virus

Infectious agent with DNA or RNA core

Retrovirus

RNA virus that uses reverse transcription

HIV

Retrovirus causing AIDS