Unit 05: DNA Replication and Protein Synthesis

Comprehensive vocabulary flashcards covering DNA structure, replication, transcription, translation, mRNA processing, and gene mutations based on the Unit 05 study guide.

Frederick Griffith

Scientist who discovered the "transforming principle" by showing that an unknown substance transferred from heat-killed, deadly S bacteria to live, harmless R bacteria, transforming them into deadly bacteria.

Oswald Avery

Scientist who performed chemical analyses on Griffith's transforming principle and concluded that DNA is the transforming principle.

Alfred Hershey and Martha Chase

Scientists who used radioactive labeling of bacteriophage DNA and protein coats to confirm that DNA, not protein, is the genetic material.

Erwin Chargaff

Biochemist who determined that in DNA, the amount of adenine equals thymine ($A = T$) and the amount of cytosine equals guanine ($G = C$).

James Watson and Francis Crick

Scientists who built the first accurate three-dimensional model of the DNA double helix and received a Nobel Prize.

Rosalind Franklin and Maurice Wilkins

Scientists whose work contributed to solving the DNA structure; Franklin produced the X-ray crystallography photograph revealing the double helix, which Wilkins shared with Watson and Crick.

Nucleotide

The monomer of nucleic acids, composed of three parts: a phosphate group, a deoxyribose sugar (in DNA), and a nitrogen-containing base.

Antiparallel

The structural arrangement where the two complementary strands of DNA run in opposite directions ($5' \rightarrow 3'$ versus $3' \rightarrow 5'$).

Phosphodiester bond

The covalent bond that links the sugar of one nucleotide to the phosphate group of another in the backbone of DNA and RNA.

Replication fork

The Y-shaped region where the DNA double helix unwinds and opens into two single strands for replication.

Helicase

The enzyme that unwinds and separates the two strands of the DNA double helix at the replication fork.

Primase

The enzyme that synthesizes a short RNA primer to initiate DNA synthesis during replication.

DNA polymerase

The enzyme that synthesizes phosphodiester bonds to build new DNA daughter strands in the $5' \rightarrow 3'$ direction, adds nucleotides to the primer, and replaces RNA primers with DNA.

Ligase

The enzyme that connects and seals nicks between Okazaki fragments on the discontinuous lagging strand.

Leading strand

The newly synthesized DNA strand that is built continuously toward the replication fork in the $5' \rightarrow 3'$ direction.

Lagging strand

The newly synthesized DNA strand that is formed discontinuously away from the replication fork in short segments called Okazaki fragments.

Okazaki fragments

Short pieces of newly synthesized DNA generated on the discontinuous lagging strand during replication.

RNA primer

A short sequence of RNA nucleotides added by primase that provides the starting point for DNA polymerase to extend.

Central Dogma of Molecular Biology

The framework describing the flow of genetic information from DNA to RNA (via transcription) and from RNA to proteins (via translation), alongside DNA replication.

Gene

A segment of DNA that contains the instructions to produce a specific protein and determine an inherited trait.

Messenger RNA (mRNA)

A type of RNA that carries genetic instructions transcribed from DNA in the nucleus to the ribosomes in the cytoplasm for protein synthesis.

Codon

A sequence of three consecutive RNA nucleotides on an mRNA molecule that specifies a particular amino acid or translation stop signal.

Transfer RNA (tRNA)

An RNA molecule that transports specific amino acids from the cytoplasm to the ribosome based on its anticodon sequence.

Anticodon

A triplet nucleotide sequence located on one end of a tRNA molecule that complementary base-pairs with a codon on mRNA.

Ribosomal RNA (rRNA)

The structural and catalytic RNA component that, along with proteins, makes up the functional subunits of ribosomes.

RNA polymerase

A complex enzyme that unwinds the DNA helix and synthesizes an RNA transcript in the $5' \rightarrow 3'$ direction using the DNA template strand.

Promoter

A specific sequence of DNA upstream of a gene where RNA polymerase and transcription factors bind to begin transcription.

Transcription

The process taking place in the nucleus where the genetic code in a DNA template strand is copied into an RNA molecule.

Translation

The process occurring in the cytoplasm at a ribosome where the sequence of codons on mRNA is decoded into an amino acid sequence to form a polypeptide.

Peptide bond

The covalent chemical bond formed between adjacent amino acids by the ribosome during translation elongation.

mRNA processing

Modifications made to pre-mRNA in the nucleus before nuclear export, including the removal of introns, splicing of exons, and the addition of a 5' cap and poly-A tail.

Introns

Non-coding segments of pre-mRNA that are cut out and eliminated during RNA splicing in the nucleus.

Exons

Coding segments of pre-mRNA that remain and are spliced together to form the mature, expressed mRNA transcript.

Frameshift mutation

A mutation caused by the insertion or deletion of nucleotides not in multiples of three, which shifts the triplet reading frame and usually results in a non-functional protein.

Missense mutation

A point mutation in which a single base change causes a codon to specify a different amino acid.

Nonsense mutation

A point mutation that converts an amino acid codon into a premature STOP codon, truncating translation and producing a non-functional protein.

Silent mutation

A point mutation in which a base substitution produces a codon that still codes for the exact same amino acid due to genetic code redundancy.