Lec 5-2 Flashcards
Types of chromosome mutations
Rearrangements
Aneuploidy
Polyploidy
Rearrangements
Mutation of structure
Parts of chromosome are duplicated, deleted, or inverted
Aneuploidy
Mutation of number
One or more chromosomes are added or deleted
Polyploidy
Mutation of number
Complete sets of chromosomes are added
Types of chromosome rearrangements
Duplication
Deletion
Inversion
Translocation
Causes of chromosome rearrangements
Crossover error or double stranded DNA breaks
Double stranded DNA breaks (dsDNA)
Can cause cell death
chromosome rearrangements
Repair machinery
Tries to repair but sometimes makes mistakes
Duplication
Section is duplicated
Deletion
Section is deleted
Inversion
Segment is turned 180 degrees
Translocation
A segment moves from one chromosome to a different homologous chromosome or to another place on the same chromosome
Causes of duplication and deletion
Unequal crossing over
Duplication and deletion causes
Red/green colour blindness
Men affected more than women
Duplication and deletion cause
Chromosome loops during prophase 1
One chromosome is normal, the other has deletion
The normal chromosome must loop in order for the homologous sequence to of the chromosomes to align
Homozygous deletions
Often lethal
Heterozygous deletions
If centromere is deleted, whole chromosome is lost
Can cause two copies of a gene to be needed for proper function
Haploinsufficiency
One copy of a gene is not enough
Duplications are important for
Evolution
Duplication evolution example
Gene A only needs one copy to function
The second copy from duplication is free to mutate
Paracentric inversions
Next to the centromere
Paricentric inversions
Arounds the centromere
Problems from inversions
Breaks may occur within a gene or regulatory region of a gene
Reduces rate of recombination during meiosis
Consequences of inversions during meiosis
Heterozygotes will encounter chromosome alignment problems during prophase 1
Loop forms
Creates aberrant chromosome
Recombinant chromatid will have chromosomes lacking many genes and will not be viable
Inversions may play a role in
Evolution
Translocations
Movement of genetic material between non-homologous chromosomes
Break may occur within a gene or regulatory region of a gene
Possible change in expression due to positional effects
Aneuploidy
Deletion of centromere during mitosis or meiosis (loss of chromosome)
Usually lethal
Nondisjunction
Failure of homologous chromosomes to separate during mitosis/meiosis
Genetic mosaicism
Produces a gyandromorph
Gynandromorph
Has multiple phenotypes for a trait
Polyploidy
Having more than 2 sets of chromosomes
Autopolyploidy
From single species
From nondisjunction in mitosis or meiosis
Allopolypoloidy
From two species
Hybridization between two species followed by chromosome doubling
Autotriploid
3n
Significance of polyploidy
Can lead to evolution: may give rise to new species
