Molecular Genetics Vocab Master List

Comprehensive vocabulary flashcards covering DNA packaging, DNA replication, transcription, translation, mutations, operons, epigenetics, biotechnology, and genetic disorders from the Molecular Genetics Vocab Master List.

genome

All of an organism's genetic material.

histone

Protein spool DNA wraps around (positive charge attracts negative DNA).

nucleosome

One "bead" = DNA wrapped around $8$ histones.

chromatin

DNA + its packing proteins; the whole "string of beads".

euchromatin

Loosely packed DNA—genes ON, being transcribed.

heterochromatin

Tightly packed DNA—genes OFF (Barr bodies, centromeres).

Barr body

The inactivated, condensed X chromosome in female cells.

telomere

Repeating junk-DNA caps (TTAGGG) that protect chromosome ends; shorten with age.

telomerase

Enzyme that rebuilds telomeres; active in gametes, stem cells, $\sim 90\%$ of cancers.

semiconservative replication

Each new DNA molecule keeps $1$ old strand + $1$ new strand.

origin of replication

The specific sequence where copying starts.

replication fork

The Y-shaped point where DNA is actively being unzipped and copied.

replication bubble

The opened-up region between two forks moving apart.

helicase

Unzips and unwinds the helix (breaks H-bonds).

topoisomerase

Relieves the twisting stress ahead of the fork so DNA doesn't knot.

primase

Lays down the short RNA primer to start things off.

RNA primer

Temporary RNA starter that DNA polymerase builds from.

DNA polymerase III

The main builder—adds nucleotides $5'-3'$ only.

DNA polymerase I

Replaces RNA primers with DNA and proofreads.

ligase

Glue—seals Okazaki fragments into one strand.

leading strand

Strand copied continuously toward the fork.

lagging strand

Strand copied in pieces (away from the fork).

Okazaki fragments

The short pieces the lagging strand is built in.

template strand

The old strand being read/copied.

transformation

Bacteria picking up foreign DNA and changing because of it.

transcription

Copying DNA to mRNA (in the nucleus).

translation

Reading mRNA and building an amino acid chain (at the ribosome).

promoter

DNA landing pad where RNA polymerase binds to start transcription.

TATA box

Part of the eukaryotic promoter that positions RNA polymerase.

mRNA

Messenger RNA—carries the code copy to the ribosome.

tRNA

Transfer RNA—brings amino acids; has the anticodon.

rRNA

Ribosomal RNA—what the ribosome itself is mostly made of.

codon

$3$-base mRNA "word" specifying $1$ amino acid.

anticodon

$3$ bases on tRNA that match the codon.

start codon

AUG—codes for methionine; always the first amino acid.

stop codon

UAA, UAG, UGA—ends translation.

release factor

Protein that binds the stop codon and frees the finished chain (adds water).

A site

Ribosome slot where the new tRNA arrives.

P site

Slot holding the tRNA with the growing polypeptide.

E site

Exit slot where the empty tRNA leaves.

peptide bond

The bond linking one amino acid to the next.

polypeptide

A chain of amino acids (folds into a protein).

ribozyme

RNA acting like an enzyme—the ribosome part that makes peptide bonds.

5' methyl cap

Modified G on the front of mRNA; protection + ribosome binding.

poly-A tail

String of A's on the $3'$ end; keeps mRNA from being degraded.

intron

Non-coding chunk cut OUT of pre-mRNA.

exon

Coding chunk KEPT in mature mRNA.

spliceosome

The machine that removes introns and joins exons.

alternative splicing

Mixing exons differently to yield different proteins from ONE gene.

reverse transcriptase

Enzyme that makes DNA from an RNA template.

cDNA

DNA copy of mature mRNA (no introns)—what you clone into bacteria.

retrovirus

RNA virus (like HIV) that copies itself into the host's DNA.

mutation

Any change in the DNA sequence.

mutagen

Something that causes mutations (radiation, chemicals, viruses).

point mutation

One nucleotide swapped for another.

silent mutation

Swap that still codes for the SAME amino acid—no effect.

missense mutation

Swap coding for a DIFFERENT amino acid (e.g., sickle cell).

nonsense mutation

Swap to a STOP codon—protein ends early, usually broken.

frameshift mutation

Insert/delete NOT in multiples of $3$—scrambles every codon after it.

reading frame

How the bases are grouped into codons.

operon

A set of related genes in bacteria controlled by one on/off switch.

regulator gene

The gene that makes the repressor protein.

operator

The on/off switch region—where the repressor binds.

structural genes

The genes that actually code for the enzymes.

repressor

Protein that blocks the operator leading to no transcription.

inducible operon

Normally OFF, turned on when its substrate shows up (lac).

repressible operon

Normally ON, turned off when its product piles up (trp).

inducer

Molecule that inactivates the repressor to turn the operon ON (allolactose).

allolactose

The form of lactose that actually flips the lac switch.

corepressor

Molecule that ACTIVATES an inactive repressor to turn the operon OFF (tryptophan).

catabolic pathway

Breaks molecules down (lac digests lactose).

anabolic pathway

Builds molecules (trp builds tryptophan).

CAP

Activator protein that boosts lac transcription—but only when glucose is low.

cAMP

Signal molecule; high when glucose is low; switches CAP on.

feedback inhibition

The end product shuts down its own production line.

transcription factor

Protein that helps control when/where genes get transcribed (eukaryotes).

enhancer

DNA sequence that speeds up transcription.

gene amplification

Making extra copies of a gene to mass-produce its protein.

acetylation

Loosens DNA off histones—genes ON.

methylation

Adds $-CH_3$ tags to DNA—genes OFF.

histone modification

Chemical tweaks that tighten or loosen DNA packing.

epigenetics

Changes in gene expression WITHOUT changing the DNA sequence; reversible.

non-coding RNA

RNA that regulates genes instead of coding for protein.

micro RNA

Micro RNA—binds mRNA and blocks its translation.

small interfering RNA

Small interfering RNA—marks mRNA for destruction.

piRNA

Piwi-interacting RNA—silences genes through protein complexes.

differential mRNA processing

Alternative splicing—different protein versions in different tissues.

mRNA stability

How long mRNA survives before being broken down (longer = more protein).

phosphorylation

Adding a phosphate group to switch a protein's activity on/off.

recombinant DNA (rDNA)

DNA combined from two or more different species.

vector

The carrier that shuttles foreign DNA into a cell (plasmid or virus).

plasmid

Small circular extra DNA in bacteria; the main cloning vector.

restriction enzyme

Molecular scissors—cuts DNA at specific palindromic sequences.

palindrome

Sequence that reads the same on both strands (like "MOM" in DNA).

sticky ends

Staggered-cut overhangs that can pair back up with a match.

blunt ends

Straight cuts—no overhang.

selectable marker

Gene (like antibiotic resistance) proving a cell took the plasmid.

origin of replication (ori)

Sequence on the plasmid so it gets copied inside bacteria.

DNA cloning

Using bacteria to mass-copy a gene or plasmid.

genetically modified organism

Organism with artificially inserted foreign genes.