Mutations and DNA Repair Mechanisms

Mutation

Change in genetic material inherited by daughter cells.

Induced Mutation

Mutation caused by environmental agents like radiation.

Spontaneous Mutation

Mutation from errors during DNA replication.

Germline Mutation

Mutation in germline cells transmitted to offspring.

Somatic Mutation

Mutation in somatic cells not passed to offspring.

Point Mutation

Change affecting a single nucleotide in DNA.

Transition Mutation

Purine to purine or pyrimidine to pyrimidine change.

Transversion Mutation

Purine to pyrimidine or vice versa change.

Silent Mutation

No change in amino acid sequence of protein.

Missense Mutation

Single amino acid change in encoded protein.

Nonsense Mutation

Codon change resulting in a premature stop codon.

DNA Damage

Alteration in DNA structure affecting function.

Phenotype

Observable traits influenced by genetic makeup.

Alleles

Different versions of a gene in a population.

Natural Selection

Process where advantageous traits increase survival.

DNA Fingerprint

Unique collection of mutations defining an individual.

Structural Genes

Genes that encode proteins through transcription.

Codon

Three-nucleotide sequence coding for an amino acid.

Amino Acid

Building blocks of proteins specified by codons.

Sickle Cell Anemia

Disease caused by a missense mutation in hemoglobin.

Frameshift Mutation

Insertion or deletion altering the reading frame.

DNA Polymerase

Enzyme responsible for DNA replication.

Early Embryonic Development

Stage when mutations can affect germline and somatic cells.

Environmental Agents

Factors like radiation that can induce mutations.

Protein Activity

Function of proteins affected by DNA mutations.

Cell Division

Process where one cell divides into daughter cells.

DNA Repair Mechanisms

Processes correcting DNA damage or replication errors.

Mutation Rate

Frequency of mutations occurring in DNA replication.

Insertion/Deletion (Indel)

Addition or loss of nucleotides in DNA sequence.

Wild-Type Sequence

Normal, unmutated DNA or RNA sequence.

Amino Acid Sequence

Order of amino acids in a protein.

DNA Repair Systems

Mechanisms correcting DNA sequence alterations.

Proofreading

First-line repair correcting errors during DNA replication.

Mismatch Repair

Fixes incorrect base pairs post-replication.

Base Excision Repair (BER)

Repairs abnormal nitrogenous bases in DNA.

Nucleotide Excision Repair (NER)

Removes bulky DNA lesions and repairs damage.

Homology Directed Repair (HDR)

Uses homologous DNA as template for repair.

Non-Homologous End Joining (NHEJ)

Directly joins broken DNA ends without template.

Uracil DNA Glycosylase (UNG)

Enzyme recognizing and removing uracil from DNA.

Apurinic/Apyrimidinic Endonuclease 1 (APE1)

Cleaves DNA at abasic sites for repair.

MutS Protein

Identifies mismatched base pairs in DNA.

MutH Protein

Distinguishes template from daughter DNA strand.

MutL Protein

Links MutS and MutH during mismatch repair.

MutU Protein

Helicase separating daughter strand at mismatch site.

ExoI Protein

Exonuclease degrading damaged daughter DNA strand.

DNA Ligase

Forms final covalent bonds in DNA repair.

DNA Double-Helix Width

2 nanometers

Bulge in DNA

Occurs with two purines paired in DNA.

Narrow DNA Helix

Occurs with two pyrimidines paired in DNA.

3' to 5' Exonuclease Activity

Ability to remove nucleotides in reverse direction.

DNA polymerase I

Enzyme that removes nucleotides at abasic sites.

Exonuclease activity

Activity that removes nucleotides from DNA ends.

Abasic site

Location in DNA missing a nitrogenous base.

DNA ligase

Enzyme that forms phosphodiester bonds in DNA.

Hypoxanthine

Nitrogenous base that can replace adenine.

Base excision repair (BER)

Repair mechanism for single damaged bases.

Nucleotide excision repair (NER)

Repair mechanism for bulky DNA lesions.

Pyrimidine dimer

Covalent bond between adjacent pyrimidines.

UvrA protein

Scans DNA for pyrimidine dimers in NER.

UvrB protein

Binds to UvrA and identifies pyrimidine dimers.

UvrC protein

Endonuclease that cuts DNA near dimers.

UvrD protein

Helicase that unwinds DNA during NER.

DNA polymerase III

Fills gaps left after DNA damage repair.

Xeroderma pigmentosum (XP)

Disease caused by defective nucleotide excision repair.

Trinucleotide repeat expansion

Increase in repeated DNA sequences over generations.

Huntington's disease

Neurodegenerative disease from CAG repeat expansion.

HTT gene

Gene associated with Huntington's disease.

CAG codon

Encodes the amino acid glutamine.

Glutamine

Amino acid encoded by CAG repeats.

Mutations

Changes in DNA sequence affecting gene function.

Mismatch repair

Corrects base pairing errors during DNA replication.

Autosomal recessive

Inheritance pattern for XP and similar diseases.

Covalent bond

Strong bond formed between atoms in DNA.

Nucleotide

Building block of DNA containing sugar, base, phosphate.

DNA helicase

Enzyme that unwinds DNA strands during repair.

5' to 3' direction

Direction of DNA synthesis and polymerase activity.

Cancer

Disease caused by mutations in DNA repair genes.

UV light

Causes pyrimidine dimers and DNA damage.