Chapter 9: Molecular Biology

Vocabulary flashcards covering DNA vs RNA, structure, replication, transcription, translation, and genetic code concepts from Chapter 9 notes.

DNA (Deoxyribonucleic Acid)

Double-stranded molecule with deoxyribose sugar and bases A, T, G, C; stores hereditary information.

RNA (Ribonucleic Acid)

Single-stranded molecule with ribose sugar and bases A, U, G, C; transfers and translates genetic information.

Deoxyribose

Five-carbon sugar found in DNA nucleotides, lacking one oxygen compared to ribose.

Ribose

Five-carbon sugar found in RNA nucleotides, containing one more oxygen than deoxyribose.

Nitrogenous Base

Adenine, Thymine, Cytosine, Guanine in DNA; Adenine, Uracil, Cytosine, Guanine in RNA.

Uracil (U)

RNA base that replaces thymine and pairs with adenine.

Double Helix

Twisted-ladder structure of DNA formed by two antiparallel strands.

Sugar-Phosphate Backbone

Alternating deoxyribose (or ribose) sugars and phosphate groups that form the sides of nucleic acid strands.

Antiparallel Strands

Orientation of DNA strands running in opposite 5'→3' and 3'→5' directions.

Hydrogen Bond

Weak attraction that holds complementary base pairs (A-T, C-G) together in DNA.

S Phase

Portion of the cell cycle during which DNA replication occurs.

DNA Replication

Process of copying DNA before cell division, producing two identical molecules.

Semi-Conservative Model

Replication method where each new DNA molecule contains one parental and one new strand.

Origin of Replication

Specific DNA sequence where replication begins.

Helicase

Enzyme that unwinds and separates DNA strands at the replication fork.

DNA Polymerase

Enzyme that adds complementary nucleotides to a growing DNA strand during replication.

Leading Strand

DNA strand synthesized continuously in the 5'→3' direction toward the replication fork.

Lagging Strand

DNA strand synthesized discontinuously away from the fork as Okazaki fragments.

Okazaki Fragment

Short DNA segment produced on the lagging strand during replication.

DNA Ligase

Enzyme that joins Okazaki fragments by forming covalent bonds in the backbone.

Central Dogma

Framework describing genetic information flow: DNA → RNA → Protein.

Transcription

Synthesis of mRNA from a DNA template inside the nucleus.

RNA Polymerase

Enzyme that builds an RNA strand using DNA as a template during transcription.

Promoter

DNA sequence where RNA polymerase binds to initiate transcription.

mRNA (Messenger RNA)

RNA copy of a gene that carries coding information to the ribosome.

RNA Splicing

Eukaryotic process that removes introns and joins exons in pre-mRNA.

Intron

Non-coding sequence removed from pre-mRNA during splicing.

Exon

Coding sequence retained in mature mRNA after splicing.

5' Cap

Modified guanine nucleotide added to the 5' end of mRNA for ribosome recognition.

Poly-A Tail

Series of adenine nucleotides added to the 3' end of mRNA for stability and export.

Translation

Process at the ribosome where mRNA codons direct amino acid assembly into polypeptides.

Ribosome

Cellular machine composed of rRNA and proteins that coordinates translation.

Codon

Sequence of three mRNA bases that specifies a particular amino acid or stop signal.

Start Codon (AUG)

Initiator codon that signals where translation begins and codes for methionine.

Stop Codon

Codons UAA, UAG, or UGA that signal termination of translation.

tRNA (Transfer RNA)

Adaptor molecule that carries specific amino acids to the ribosome based on codon-anticodon pairing.

Redundant Coding (Degeneracy)

Property of the genetic code where multiple codons can specify the same amino acid.