Chromosomal Mutations Flashcards
Chromosomal Abnormalities
Chromosomal Abnormalities
Total number of chromosomes different
Deletions of Multiple genes
* Depending on size of segment deleted
Duplications of multiple genes
* Depending on size of segment duplicated
Rearangemnt of Chromosomal Sections
* Within one chromosome
* Or between two diferent chromosomes
Wrong Number of Chromsomes
Wrong Number of Chromsomes
Aneuploidy
* Gain or loss of an entire chromosme
* Compaires against euploid Number = normal number of chromosomes
Polploidy
* Gain of an entire set of chromsomes
* Much more sever mutation becuase 3 or more of all chromosmes - therefore all genes in entire genome
Non-Disjunction
Non-Disjunction
Failure of random seperation of either sisterchromatids or homologus chromsomes
Can occur in Meiosis 1 or 2
* Leading to aneuploid gametes
Or can occur in Mitosis
* Leading to aneuploid somatic cells
* can be a cause of cancer
Autopolyploidy
Autopolyploidy
An extra set(s) of chromosomes identical to the haploid set for this species
Can arrise from:
* Non-disjucntion of all chromosomes during meiosis - producing a diploid gamete
* Two sperm fertelizing one egg
* Cell goes through S phase with out M phase - duplication without division
Allopolyploidy
Allopolyploidy
An extra set(s) of chromosomes from a different species
Can arrise from:
* Hybridization of two closley related species trying to mate
* Wont happen in animals becuase of blocks to cross-species mating
* Hybrids ocur naturally in plants
* Normally hybrid is sterile (even in plnats)
* But if hybrid undergoes autopolyploidy and somehow doubles chromosomes - becomes tetraploid (4N)
Deletion
Deletion
- Part of the chromosome is lost
- if the loss contains centromere, entire chromosome will be lost during mitosis
- Severity of phenotype depends on size of the pieace of the chromosome that was lost
Duplication
Duplication
Part of the chromosme is copied and present twice
Can arrise from:
* Unequal crossing over of homologus chromsomes during meiosis
* A replication error that re-coppies part of the sequence during S phase
Gene Redundancy
Gene Redundancy
- A single gene sequence encoded in multiple copies at different locations in a single genome
- Some genes are used so often that evolution has selected multiple copies of the gene sequence
- Extra prtoein can be made constantly from each number of sites
Gene Amplification
Gene Amplification
- Certian gene sequence is replicated repeatedly during S phase
- Some genes are used so often that evolution has selected the gene to be replcated over and over again
Inversion
Inversion
Chromosomal error where a piece of the chromosome flips within the chromosome
DNA Sequence is not lost but inverted
Inverions can change:
* Gene order
* Centromere Position
* Break a Gene
* Seperate gene from regulatory sequence
Arrise from two break points and subsuquent reinsertion
* Paracentric - centromere is not part of inverison
* Pericnetric - centromere is included within the inversion
Inversion
Inversion
Chromosomal error where a piece of the chromosome flips within the chromosome
DNA Sequence is not lost but inverted
Inverions can change:
* Gene order
* Centromere Position
* Break a Gene
* Seperate gene from regulatory sequence
Arrise from two break points and subsuquent reinsertion
* Paracentric - centromere is not part of inverison
* Pericnetric - centromere is included within the inversion
Inversion
Inversion
Acentric
* Chromosome lacking a centromere
* Crossing over of paracentric inversion
Disentric
* Chromosome with two centromeres
* Crossing over of paracentric inversion
Translocations
Translocations
- Crossing over between non homologus chromsomes
- Leads to a chromosonal segment ending up in the wrong place
Reciprocal Translocations
* Exchange information between two non homologus chromsomes
Robertsonian Translocations
* Small pieces lost, fusion of two longer pieaces
Fragile X Syndrome
Fragile X Syndrome
Most common from an inherited mental restardation (MR)
* Gene FMR-1
* Contains a trinucleotide repeat -CGG
In the unstable region imediatley upstream of the coding sequence
* Regulatory region of FMR-1
Number of copies of the trinucleotide repeat (CGG) correlated with phenotype
* Less the 50 = normal
* 50-200 = carriers
* 200 or more = Fragile X syndrome
