monosomy unmasks ____recessive lethalswhen one copy is not sufficient for organism to survivehaploinsufficiency- 2n + 1 chromosomes
- addition of chromosome produces more viable organismstrisomytrisomies for autosomes are often...lethaltrisomy of chromosome 21
- has 12 to 14 characteristics
- on average affected individuals express 6-8 characteristicsdown syndromeDSCRdown syndrome critical regioncritical region of chromosome 21DSCRare genes dosage sensitiveyesDSCR is responsible for many _____phenotypic associated syndromesorigin of extra 21st chromosomehomologs do not disjoin in anaphase i or ii(origin of extra 21st chromosome)
-- homologs do not disjoin in anaphase i or ii which leads to ___ gametesn+1what is the source of 95% of trisomy casesovumtrisomy chances increases with increasing...maternal agemore than two multiples of haploid chromosomes foundpolyploidyhas 3n chromosomestriploidhas 4n chromosomestetraploidhas 5n chromosomespentaploid(origin of polyploidy)
addition of one or more sets of chromosomes identical to the haploid complement of same speciesautopolyploidy(origin of polyploidy)
combination of chromosome sets from different species as a consequence of hybridizationallopolyploidyeach identical set of chromosomes is identical to parent speciesautopolyploidyhow does autopolyploidy arise-diploid gamete is produced
-two sperm fertilize one ovumchromosomes have replicated, but the parent cell never divides and instead reenters interphase, the chromosome number will be doubledautotetraploidautotetraploid is experimentally induced bycolchicineresults from hybridizing two closely related speciesallopolyploidyin allopolyploidy hybrid plant may be sterile because it cannot produce...viable gametesin allopolyploidy, chromosomes are not homologous and cannot...synapse in meiosispolyploidy contains equivalent of four haploid genomes derived from separate speciesallotetraploidis the original species known in allotetraploidnocondition where only certain cells in diploid organism are polyploid
- set of chromosomes replicates repeatedly without nuclear division
- can occur in cancer cellsenopolyploidychromosome rearrangement includesdeletions, duplications, inversions, nonreciprocal translocations, reciprocal translocationsalteration of chromosomes includesdeletions, duplications, inversions, translocationstotal amount of information in chromosome changesdeletions and duplicationsgenetic material remains the same but rearrangedinversions and translocations- missing regions of chromosomes
- chromosome breaks in one or more places
- poriton is lostdeletionsterminal of deletion can ...varydeletion near one endterminal deletiondeletion on interior or the chromosomeintercalary deletionsynapsis between chromosome with large intercalary deletion and normal complete homologcompensation loopcompensation loop requires unpaired region of normal homolog to loop out of linear structure intodeletion or compensation loopdeletion of small terminal part of chromosome 5cri du chat syndromewhat kind of deletion is cri du chat syndromesegmental deletioninfants with cri du chat syndrome exhibit...anatomical malformationsrepeated segment of chromosome
- single locus is present more than once in genome
- can produce compensation loopduplicationsduplications arise from ___ between synapsed chromosomes during meiosisunequal crossing overduplications cause ...phenotypic variation____ phenotype in drosophila results from duplicationbar-eyebar-eyed flies have narrow slit like eyes
- bar mutation is ____inheritedgene duplication may play a role in...evolutiongene duplication hypothesized to be a major source ofnew geneswhat is an example of gene duplication palying a role in evolutiongenes encoding digestive enzymes trypsin and chymotrypsinrearrangement of linear gene sequence
- no loss of genetic information
- segment of chromosome turned 180 degrees w/in chromosomeinversioninversion requires __ breaks in chromosomes, and ____ inverted segmenttwo, reinsertioninversion can arise from ___chromosomal looping- does not change lengths of two arms of chromosome
- centromere not part of inverted segmentparacentric inversion- centromere is part of inverted segment
- does change lengths of two arms of chromosomespericentric inversioninverted and noninverted chromosomes in meiosis paired only if they form an inversion loopinversion loops- organisms with one inverted chromosome and one non-inverted homolog
- can be paracentric or pericentricinversion heterozygotes-crossover between pericentric and non inverted homolog
- recombinant chromatids have duplications and deletionspercentric inversion crossovermovement of chromosomal segment to new location in genometranslocation- involves exchange of segments between two non homologous chromosomes
- genetic information is lost or gained
- has unusual synapsis configuration during meiosisreciprocal translocationtwo possible segregation patternsalternate segregation, adjacent segregationsegregation pattern at first meiotic division
has complete complement of genetic informationalternate segregationLeads to gametes containing duplications and deficiencies
if these participate in fertilization in animals, the resultant offspring do not usually surviveadjacent segregationparents with adjacent segregation havesemisterilityinvolves breaks at extreme ends of short arms of two non homologous acrocentric chromosomes
small segments are lost
large submetacentric or metacentric chromosomes are producedrobertsonian translocation (centric fusion)example of robertsonian translocationfamilial down syndromemore susceptible to chromosome breakage when cultured in the absence of folic acid or other chemicals
- sites indicate regions or nontightly coiled chromatinfragile sitesfolate-sensitive site on X chromosome exhibit ...FXSmost common form of inherited mental retadation; dominant traitFragile X syndromeanother term for fragile x syndromemartin bell syndromefragile x syndrome is caused by trinucleotide repeats in ...FMR1 genea sequence of three nucleotides is repeated many times, expands the size of the genetrinucleotide repeatsthe number of trinucleotide repeats increases with every generationgenetic anticiptation55 to 230 trinucleotide repeats is consideredcarrier statusover 230 trinucleotide repeats is consideredsyndrome statuslink between autosomal fragile sites and ___ reportedlung cancerdefect is associated with the formation of ___tumors___ gene on fragile site location, ____ altered or missing in lung cancer ellsFHIT, FRA3B
