2 Chromosome Morphology MetacentricCentromere is centrally located; arms equal lengthSubmetacentricCentromere is off centerAcrocentricCentromere is close to one enda long arm and a knob, or satellite, at the otherTelocentricCentromere is at one endNot present in humansOn human chromosomes, the short arm is designated by the letter p and the long arm by the letter q.
3 Karyotype Complete set of chromosomes arranged in homologous pairs Sample is from an actively dividing cellChemical inhibits spindle assembly formationCell can not complete mitosisHypotonic solution swells cellAllows chromosomes to spread outDropped on slide and stainedA picture of metaphase chromosomes lined up in descending order of their size
4 Staining G banding C banding R banding Q banding Giemsa stain; most commonStains A-T rich regionsC bandingStains centromeric heterochromatin and portions of chromosomes with large sections of heterochromatinR bandingStains G-C rich regionsGives opposite banding pattern of G bandingQ bandingUV light is usedSame pattern as G banding
6 Types of chromosome mutations Chromosomal rearrangementStructure is alteredAneuploidyAbnormal number of chromosomesMissing one or more/having one or more extraPolyploidy1 or more additional sets of chromosomes
8 Duplications Section of chromosome is doubled Tandem Displaced Reverse Repeated segment is right after the originalDisplacedRepeated segment is located elsewhere on chromosome, or on a different chromosomeReverseSequence is inverted from the original sequence
9 Duplications Heterozygotes During paring of homologous chromosomes, duplicated region loops outOffspring receive two copies of involved genes from parent with duplication, and a third copy of the other parentPartial trisomy for all involved genesAlters gene dosageabnormal gene dosage: imbalances in the amounts of gene products
11 Deletions Loss of a portion of chromosome If the deleted region includes the centromere, entire chromosome will be lostUsually lethal in homozygous formHeterozygotesNormal chromosome must loop out during pairingPartial monosomy for all involved genes
12 Deletions - heterozygotes Affects gene dosagePseudodominanceExpression of mutant/recessive phenotype due to loss of normal/dominant copyHaploinsufficiencyBoth copies of the gene are needed to manufacture adequate amount of gene productOne gene doesn’t produce enough for a normal phenotype
13 Inversions Two breaks in chromosome, then flipped and reinserted Paracentric inversionBoth breaks occur in one armPericentric inversionBreaks on both arms; centromere is involvedCan change morphology by altering centromere positionEffectsDisruption of a gene – no functional productPosition effectChange in gene position can affect gene expression
14 Inversion loops Chromosomes have to loop when pairing Paracentric inversion loopsIf crossing over occurs within loop:Creates a dicentric chromosome and an acentric chromosomeAcentric is lostDicentric forms a dicentric bridge, and breaksNonviable recombinant gametes
16 Inversion loops Pericentric inversion loops Crossing over within loop creates recombinant chromosomes with duplications and deletionsnonviable
17 TranslocationsRearranges genetic material to another part of the same chromosome; or nonhomologous chromosomeNonreciprocalSegment moves from one chromosome to anotherReciprocalExchange between two chromosomesEffectsLoss of gene function – breakPosition effectCreation of a fusion/abnormal protein
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