Chromosomal and Genetic Mutations: Definitions and Mechanisms in Biology

Chromosome Rearrangement

Structural change in a chromosome without changing chromosome number.

Duplication

Repeated chromosome segment, often from unequal crossing over.

Deletion

Loss of a chromosome segment.

Pseudodominance

Expression of recessive allele due to deletion of dominant allele.

Haploinsufficiency

One gene copy is insufficient for normal function.

Inversion

Chromosome segment flipped 180 degrees.

Paracentric Inversion

Inversion not including centromere.

Pericentric Inversion

Inversion including centromere.

Translocation

Movement of chromosome segment to non-homologous chromosome.

Reciprocal Translocation

Exchange between two chromosomes.

Robertsonian Translocation

Fusion of two acrocentric chromosomes at centromere.

Fragile Site

Chromosomal region prone to breakage.

Aneuploidy

Gain or loss of individual chromosomes.

Nondisjunction

Failure of chromosomes to separate properly.

Nullisomy

Loss of both chromosomes of a pair (2n-2).

Monosomy

Loss of one chromosome (2n-1).

Trisomy

Extra chromosome (2n+1).

Polyploidy

More than two complete chromosome sets.

Autopolyploidy

Extra sets from same species.

Allopolyploidy

Extra sets from hybridization of different species.

Uniparental Disomy

Both chromosome copies inherited from one parent.

Genetic Mosaicism

Genetically different cell populations in one individual.

Plasmid

Small circular DNA molecule replicating independently

F Factor

Plasmid controlling conjugation.

Conjugation

Direct DNA transfer via sex pilus.

Transformation

Uptake of free DNA from environment.

Transduction

DNA transfer via bacteriophage.

Bacteriophage

Virus that infects bacteria.

Lytic Cycle

Virus replicates and lyses host cell.

Lysogenic Cycle

Viral DNA integrates into host genome.

Prophage

Integrated viral DNA in host genome.

Retrovirus

RNA virus that reverse-transcribes RNA into DNA.

Reverse Transcriptase

Enzyme that makes DNA from RNA template.

Nucleotide

Basic unit of DNA.

Complementary Base Pairing

A pairs with T; G pairs with C.

Phosphodiester Bond

Covalent bond linking nucleotides.

Nucleosome

DNA wrapped around histone proteins.

Euchromatin

Loosely packed, transcriptionally active DNA.

Heterochromatin

Tightly packed, transcriptionally inactive DNA.

Centromere

Region where spindle fibers attach.

Telomere

Chromosome ends with repeated sequences.

Transposable Elements

DNA sequences that move within genome.

Semiconservative Replication

Each daughter DNA has one old and one new strand.

DNA Polymerase

Enzyme that synthesizes DNA.

Replication Fork

Y-shaped region where DNA is unwound.

Leading Strand

Synthesized continuously.

Lagging Strand

Synthesized discontinuously.

Okazaki Fragments

Short DNA fragments on lagging strand.

Helicase

Enzyme that unwinds DNA.

Primase

Synthesizes RNA primer.

DNA Ligase

Seals DNA fragments.

Telomerase

Extends telomeres using RNA template.

Holliday Junction

Four-stranded crossover structure during recombinatio