Transcription & Mutation & DNA Repair - Vocabulary Cards

50 vocabulary flashcards covering mutation, DNA repair, transcription, RNA processing, and basic gene structure.

Mutation

An un-repaired change or error in the DNA sequence, caused by replication errors, spontaneous base changes, or induced by chemicals/radiation; mutations occur daily in cells.

Genome

The complete set of genetic material in an organism; the total DNA content inside a cell, often described as about 3 billion base pairs in humans.

Gene

A specific segment of DNA that contains instructions to make a particular protein or functional RNA; the functional unit of heredity.

Nucleotide

The basic building block of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base (A, T, C, G in DNA; A, U, C, G in RNA).

Point mutation

A mutation that involves a single nucleotide change in the DNA sequence.

Transition mutation

A point mutation where a purine replaces another purine (A↔G) or a pyrimidine replaces another pyrimidine (C↔T).

Transversion mutation

A point mutation where a purine is replaced by a pyrimidine or vice versa (e.g., A↔T or C↔G).

Deletion

A mutation in which part of a chromosome or DNA sequence is removed.

Duplication

A mutation in which a segment of DNA is copied and inserted, resulting in extra copies.

Inversion

A mutation where a segment of DNA is reversed end to end within the chromosome.

Insertion

A mutation in which a segment of DNA is added into a chromosome.

Translocation

A chromosomal mutation where segments are moved from one chromosome to another.

Mismatch repair (MMR)

DNA repair system correcting replication errors; involves Mut proteins (MutS, MutL, MutH) and reduces error rate; defects linked to diseases like HNPCC.

MutS

A Mut protein that recognizes mismatched bases during mismatch repair.

MutL

A Mut protein that acts as a mediator/coordinator in mismatch repair.

MutH

A Mut protein that nicks the newly synthesized strand near a mismatch to initiate repair (in bacteria).

Excision Repair

A group of DNA repair pathways that remove damaged DNA and replace it with correct sequence; includes NER and BER.

Nucleotide Excision Repair (NER)

Repair system that removes a nucleotide-containing damage (such as pyrimidine dimers caused by UV) by excision of a short single-stranded DNA segment.

Base Excision Repair (BER)

Repair system that removes a damaged base and leaves the sugar-phosphate backbone intact; followed by replacement with the correct base.

Double-Strand Break Repair (DSBR)

Repair of breaks in both DNA strands; includes pathways like NHEJ and HR.

Non-Homologous End Joining (NHEJ)

A quick, often error-prone DSBR pathway that directly joins broken DNA ends without a homologous template; essential for cell survival.

Homologous Recombination (HR)

Error-free DSBR pathway that uses a homologous DNA template (usually the sister chromatid) to accurately repair breaks, mainly in S/G2.

BRCA1/BRCA2

Genes involved in homologous recombination; mutations increase cancer risk (notably breast/ovarian cancer) due to impaired HR.

RNA

Ribonucleic acid; predominantly single-stranded in the cytoplasm, with ribose sugar and bases A, G, C, U.

DNA

Deoxyribonucleic acid; double-stranded molecule with deoxyribose sugar and bases A, T, C, G; forms the genetic material in nearly all organisms.

RNA polymerase

Enzyme that synthesizes RNA from a DNA template; bacteria have one main RNAP, eukaryotes have RNAP I, II, and III; often depicted as a holoenzyme with sigma factor.

DNA polymerase

Enzyme that replicates DNA by adding nucleotides to a growing DNA strand during replication.

Promoter

DNA sequence upstream of the transcription start site that signals where RNA polymerase should begin transcription.

Sigma factor

Protein that recognizes promoter sequences (-10 and -35 in bacteria) and helps RNA polymerase initiate transcription.

-10 box (TATA box / Pribnow box)

Promoter element located about 10 bases upstream of +1 in bacteria; helps recruit RNA polymerase via sigma factor.

-35 box (TTGAC box)

Promoter element located about 35 bases upstream of +1 in bacteria; part of promoter recognized by sigma factor.

Transcription Start Site (+1)

Nucleotide position where transcription begins; the first RNA nucleotide is incorporated.

Upstream

Region of DNA located before the transcription start site; negative numbering (−10, −35).

Downstream

Region of DNA located after the transcription start site; positive numbering (+1, +2, …).

Template strand

The DNA strand read by RNA polymerase to synthesize a complementary RNA; also called antisense or non-coding strand.

Coding strand

DNA strand whose sequence corresponds to the RNA transcript (with T in DNA replaced by U in RNA); also called sense or plus strand.

Cap (5' cap)

7-methylguanosine cap added to the 5' end of eukaryotic mRNA to protect from exonucleases.

5' UTR

5' untranslated region; non-coding segment upstream of the coding sequence in mRNA.

3' UTR

3' untranslated region; non-coding segment downstream of the coding sequence in mRNA.

Poly-A tail

A string of adenine nucleotides added to the 3' end of eukaryotic mRNA to stabilize and protect it.

Spliceosome

RNA-protein complex (U1, U2, U4, U5, U6) that removes introns and ligates exons during mRNA processing.

Intron

Non-coding sequence within a gene that is removed during RNA splicing.

Exon

Coding sequence in a gene that remains in mature mRNA after splicing.

Monocistronic

mRNA that encodes a single protein; typical of eukaryotic genes with their own promoter.

Polycistronic

mRNA that encodes multiple proteins; common in prokaryotes within operons.

Operon

A cluster of genes regulated by a single promoter; typically polycistronic in prokaryotes.

Cistron

Another term for a gene; a unit of hereditary information.

mRNA

Messenger RNA; carries the genetic information from DNA to the ribosome for protein synthesis.

tRNA

Transfer RNA; adaptors that bring amino acids to the ribosome; has an anticodon and the CCA aminoacyl end.

rRNA

Ribosomal RNA; core component of ribosomes; essential for protein synthesis; prokaryotic and eukaryotic rRNA differ in types and sizes.