*genome Evolution And Multigene Famillies Flashcards
How can using synteny blocks help understand chromosomal rearrangements in evolution
Synteny blocks comparing genomes shows the homologous genes in different organisms
Those with less regions of synteny show chromosomal rearrangements via evolution
Name 4 main ways chromosomes rearrange
1- reciprocal translocation
2- chromosome fusion
3- robertsonian translocation
4- inversion
What is reciprocal translocation as a method of chromosomal rearrangements
Where 2 non homologous chromosomes exchange fragments of genes
Eg like in meiosis
Can produce unbalanced meiotic products
Acute myeloid leukaemia is an example of reciprocal translocation as genes on 8 and 21 exchanged. How is this causing problems
The Gene for AML transcription factor is replaced with an ETO fusion protein which interferes with the transcription factors function
The transcription factors function therefore not working and rbc don’t get produced
What is a dominant negative mutation
Where an altered product of reciprocal recombination eg the eto protein in AML act antagonistically to the genes allele and interests with the function
How is chromosome fusion an example of chromosomal recombination
Where 2 telocentric chromosomes fuse to produce 1 chromosomes
This person now has 45 chromosomes instead
What is robertsonian translocation and why doesn’t it result in any genetic material loss
Where short arms of 2 Acrocentric chromosomes are lost and the chromosome then fuses producing 45 chromosomes in karyotype
No genetic material is lost as the P arm doesnt have much genetic material just repeats
What happens due to robertsonian translocation during meiosis
Aneuploidy or trisomy generated
What is the difference between para centric and Pericentric inversions of genes (another type of chromosome rearrangement)
Para centric is where inversion of genes occurs in 1 arm of chromosome
Pericentric is where inversion occurs involving both arms and centromere
How do chromosomal rearrangements occur ?
By random in errors in eg dna replication, recombination and repair processes
What 2 ways could you increase genome complexity
Either small gene duplications
Or duplications of entire genomes
How is crossover and sister chromatids exchange unequal?
When the 2 sister chromatids line up the repeating units of dna dont line up correctly
When the strands break on non sister chromatids there is unequal number of repeating units transferred
Why is duplication of a whole gene favourable in terms of selective pressures and natural selection
They will have an extra set of genes. This means that when a mutation occurs in one gene to perform another function, the other gene is still conserved and retains old function
= better suited
What are multigene families and how do they come about
Where duplication events with of full genome or regions cause multiple genes
These genes then evolve by mutation to have specialised functions (paralogue)
How are hox genes an example of a multi gene family where there are alterations between genes and expression
Hox genes are found in clusters on chromosomes
They encode for transcription factors needed for expression of genes in different times in development
They are all evolved from eachother to encode transcription factors at different parts of development depending where on the cluster they are located
Eg first gene will be expressed first
