BIOL 302 Genetics Lecture 15: Chromosome Abnormalities and DNA Mutation

Epigenic Modification

Altering of Histones in Nucleosomes (Etc, addition of methyl groups for tightening, acetyl groups for loosening)

Metacentric Centromere

Centromere is close to center of chromosome

Submetacentric Centromere

Centromere is between terminal end and center of chromosome

Arocentric

Centromere is close to terminal end of chromosome

Telometric Centromere

Centromere is at the end of chromosome, no p or q arm

P arm of Chromosome

Short end of chromosome

Q arm of chromosome

Long end of chromosome

Giesma Banding

Type of chromosome banding used to identify human karyotypes

FISH (Florescent in situ hybridization)

Provides different colors for chromosome pairs, can be used to detect microdeletions

Euchromatin

Regions of chromosome less condensed during interphase, contains less actively expressed genes

Heterochromatin

Condensed regions of chromosome

Facultative: sometimes condensed, sometimes non condensed

Constitutive: Always condensed, usually near centromere or telomeres

Interchromosomal Domain

Region in nucleus where transcriptionally active parts are found

Chromosome Territory

Early replicating parts found near center, later ones found near peripheral

Centromere Structure

Composed of kinetochore proteins and spindle microtubles, constitutively heterochromatic

Nondisjunction: Meiosis I

Failure of chromosomes to seperate in anaphase of meiosis I, leads to all offspring to be aneuploid, with either (2n+1) or (2n-1) after gamete addition

Nondisjunction in Meiosis II

Failure of chromosomes to seperate during anaphase of meiosis 2, leading to half of the offspring to be aneuploid (one 2n+1, the other 2n-1 after gamete addition)

Klinefelter syndrome

Chromosome 47, XXY Trisomy

Jacob Syndrome

Chromosome 47, XYY Trisomy

Triple X syndrome

Chromosome 47, XXX Trisomy

Turner Syndrome

Chromosome 45, XO

Intersitial Deletioin

Partial chromosome deletion caused by a chromosome breakage at 2 points

Unequal Crossover

Misalignment of chromosomes during cross over, results in the partial deletion of one chromosome and the partial duplication of another

Paracentric Inversion

Centromere is outside the inverted region that is reattached

Pericentric Inversion

Centromere included in the inverted region that is reattached

Inversion Loop

Caused by alignment of normal and inverted homolog, crates a dicentric chromosome leading to a loss of the acentric fragment

Unbalanced Translocation

Translocation of fragment to another non-homolog, with no swap

Balanced Translocation

Swap of fragments of non homologs

Mutation Hotspot

Gene where mutations occur at an elevated frequency, usually cause by a larger gene size

Base pair mutation

A base pair of a codon-anticodon is swapped

Transition Mutation

A pyramidine/purine nucleotide is swapped with another (C→U, G→ A)

Transversion Mutation

A purine is swapped with a pyramidine, or vice versa (C/U/T→G/A)