Flashcards in Lecture 9 Deck (40):
What are the 2 type of chromosomal mutations
structural and number
Changes in chromosomal number are refereed to as
Structural mutations involve
novel sequence rearrangements within 1 or more DNA molecule
Why are chromosomal mutations important x5
- understand how genes work together
-insights into meiosis and chromosome architecture
-tools for genomic manipulation
-cause of genetic diseases
-insights into evolutionary processes
Types of chromosomal mutations x3
-loss of genetic material
-gain of genetic material
-relocation of genetic material
What causes loss of genetic material (x2)
what causes a gain in genetic material (x2)
What causes relocation of genetic material (x2)
How do you form a deletion?
A chromosome segment can be lost
How do you form a duplication?
a section can be doubled
What sort of breaks are lethal unless repaired, and how can chromosomal rearrangement result from this
Double-stranded breaks; If ends of 2 different breaks are joined a chromosomal rearrangement can result
What does a DNA molecule have to have to survive meiosts
What is nonallelic homologous recombination
Crossing over between duplicated DNA sequences (this causes rearrangements)
How can crossing over occur between non-homologous chromosomes
Repeat sequences on different chromosomes (or within 1 chromosome)
If crossing over occurs between repeat DNA sequences that are not if in the same position on homologs then what can be produced?
Why is a deleted segment often lost?
Because it has no centromere
What's a terminal deletion
Segment deleted at the end of a chromosome
What's a interstitial deletion
segment deleted within a chromosome
a small deletion within a gene that inactivates the gene
Involve several genes and their consequences are more severe
When is a loop formed by a chromosome
In meiosis the chromosome of a deletion heterozygote
What are the consequences when a multigenic deletion is made homozyous by inbreeding
What sort of mutations never revert back to the wildtype
Pseudodominance (to do with deletions)
Deletions allow the expression of phenotypes carried as recessive alleles
Duplications that are adjacent
Duplications that are located elsewhere (not adjacent) in the genome
If a duplication has occured, how many copies of that chromosome region will a diploid cell have
What does detection of duplications involve?
Looking for duplications of chromosome banding patterns + the presence of loops at meiosis in heterozygous individuals
Describe the Bar mutation (4 main points)
-Mutation in Drosophila
-that have reduced facests in the eye, making the eye smaller
-the trait is inherited as an incomplete or partial dominant X linked train
-Heterozygous females have smaller eyes, while even smaller is that of homozygous females and hemizygous males
(see image in slides)
Duplications that range in size from 10-50 kbp and encompass whole genes and the regions between them.
-Most segemental duplications are dispersed but some are tandem.
-About 4% of the genome consists of segmental duplications
The centromere will be outside the inversion
The centromere is inside the inversion
Are people with inversions usually normal or not?
Yes because inversions dont change the overall amount of genetic material
Para or peri centric inversions cause the formation of a dicentric bridge
What's an inversion loop
During meiosis 1 chromosome twists at the ends of the inversions so that it can pair withe the untwisted homolog
In para or peri centric inversions does an acentric fragment form
paracentric - this fragment is lost because it has no centromere
In para or pericentric inversions can crossing over result in duplications and deletions result
Explain what it is meant by: Inversions act as crossover supressors
They dont stop crossing over happening, you just dont see any crossover product as they are not viable
Explain what it is meant by: Inversions can lead to the creation of 'Super Genes'
Gene are linked, can not be broken up as no crossing over